​Now that Samsung Electronics (005930.KS) has begun offering its 2022 line of Mini-LED/QD and QD only TVs (or at least in part), we can look at how TV set pricing has progressed with last year’s models and how the new line’s pricing compares with 2021 pricing.  We note that while this is a microcosm of the TV space, it is at least a representation of how companies adjust TV set prices, particularly in the premium category and how seasonality and other factors affect that pricing.  The 2022 Mini-LED/QD and QD only line is essentially the same as the 2021 line other than the elimination of the 70A (2021) class, which consisted of four sizes of 4K Quantum Dot TVs.  Given that the series above (80A) and below (60A) duplicated all of those sizes and provided almost the same combination of features at similar prices, we expect Samsung saw no need to bring back that line.

When Samsung began to accumulate TV panels for the Mini-LED/QD line last year TV panel prices were on the rise (Figure 1), while this year TV panel prices had fallen considerably from the highs reached in July of last year.  Based on February Aggregate TV panel pricing, TV panels acquired in February 2022 were 38.8% lower in price than during the same period last year, while offsets would be rising component, silicon, and transportation costs, but Samsung has lowered the initial price of this year’s models by only 6.7%, with the bulk of the reductions in the lower price tier Mini-LED/QD line (85 Series) and the higher prices QD only line (80 Series).  Due to the potential for feature changes and potential cost offsets mentioned above in the 2022 line, it is difficult to understand exactly how much of the panel cost savings Samsung has passed on to consumers, at least as part of initial 2022 pricing, but we assume they continue to capture considerably more margin on this line than on the more generic standard LCD TV line.  We expect also that Mini-LED backlight costs are lower on a y/y basis as the number of suppliers has increased.
Based on the rate of change data (Figure 1) for the entire line, we expect to see price reductions as soon as the end of May, with the biggest price drops in June/July (summer sales), for Columbus Day in October and the Thanksgiving Holiday.  That said, the single largest overall price decline came in February of this year, usually due to a push to reduce previous year inventory as new models go into production.  The worst time to buy, at least from this sample, is right before Christmas, as desperate gift buyers tend to be more willing to pay a premium as time runs out, and similarly just before Chinese New Year, likely for the same reason.  Most significant however, is the fact that in the 328 days since the 2021 line became available the aggregated price of the entire line has decreased by 29.6% from initial prices, and 27 of the 35 models are currently at their lowest price point (one is at its highest), and across the top of the line (900 Series), which are 8K Mini-LED/QD sets, that group is down 46.7% from its initial pricing.

​With Super Bowl LV! Coming this Sunday, we thought it might be a good time to check on TV prices, given the “Deals, deals. Deals…” type advertising that is being promoted on just about every possible media type.  Since we have detailed historical data for Samsung Electronics (005930.KS) Mini-LED/QD TV line (2021 only as 2022 sets have been announced but not priced of released) we updated that data to see if the deals being offered for the Super Bowl are as good as some of the advertisements proclaim.
As we have previously noted there are 35 TV set models in the group we have been following, consisting of 6 8K Mini-LED/QD TVs, 11 Mini-LED/QD 4K TVs, and 18 QD only 4K TVs.  Pricing was released on May 20, 2021 and we have collected data 21 times since then, with the last being yesterday.  While two models were at their highest price, the $15,000 98” (QN98QN90AFXZA), a set that has not changed price since its initial release, and the least expensive QD only 32” model, which currently sells for $500 and has for most of its life, but dropped to $400 during the period around Black Friday.  Aside from those two, 22 of the 35 models are at their lowest price since release, although only 5 of those are lower than any previous low price, including those reached during the holidays, so while the discounting seen for the Super Bowl has brought many models down to their lowest prices, only 5 of those are lower than at any point in the model’s history.
We do note that the current discounts seen for Samsung’s 2021 Mini-LED/QD line are considerable against the previous pricing (1/18/22) in some cases, ranging from a low of 0.0% to a high of -26.7%, most have been seeing increases after the November/December holiday period, so while those discounts look good on a percentage and dollar basis, most are back to the same spot seen during the holidays.  We also note that Samsung has announced their new 2022 line, although pricing and release dates have not been set, so there is some incentive for discounting to move older inventory to make way for the new line.  All in, while not the perfect time to buy a TV set (ideally, the period around Black Friday), prices are certainly better than they have been for the last few months, down an average of 25.8% across the line, against original pricing and the biggest single period drop (-8.0%) (period/period) during any pricing period, including the 7.1% drop seen October 20, which began the holiday discounting.  Of course, the last two pricing periods saw increases of 4.9% and 4.2%, so in most cases prices are just back to their previous lows, but the data says its not a bad time to be buying a TV, especially a relatively high end TV as long as it doesn’t cut too deeply into the chips and dip budget.

QD III.5
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​One point that we feel obligated to make concerning quantum dots is safety.  The highest efficiency quantum dots are based on Cadmium Selenide.  Cadmium is a metal similar to zinc, however it is extremely toxic to humans and the environment, with indications that cadmium mining operations going back to pre-WW II had contaminated water sources, leading to health problems for local populations.  It is one of only 6 materials banned by RoHS (EU Restriction of Hazardous Substances) and is considered a carcinogen by the International Agency for Research on Cancer.  There are alternatives to using Cadmium in quantum dots, with Indium and Zinc among the alternatives, although they do not have the same characteristics. 
While both Cadmium based and Cadmium free QDs are produced, we found it unusual that there was a very significant disparity between where each type of QD is used.  According to the largest supplier of QDs globally, Cadmium free quantum dots are used in almost all display products produced by non-Chinese display producers, while Chinese display products seem to use Cadmium based QDs.  There is a cost to using Cadmium free QDs, as they tend to be more expensive and less efficient, but are free of toxic materials, so one might look at the trade-off between the development and use of Cadmium free QDs as one that has slowed the overall development of QDs over time.  That said, we would rather see the development of Cadmium free QDs as a global standard than a bifurcated development scenario even if it extends the developmental timeline. 

​In previous notes we have spoken about quantum dots and some of the current and future applications that present themselves for quantum dots, but in all of the application mentioned previously the dots have been stimulated optically, that is by the light coming from another source.  In some cases it was from LEDs (QDEF film or Mini-LED/QD), in some cases it was from OLED (QD/OLED), and in the future it could be from micro-LEDs, but in each of these applications, the quantum dots were shifting colors as they were being stimulated by optical sources.  Quantum dots have another characteristic that gives them a potential life even further down the road and that is the ability to be a self-emissive light source without being stimulated by another optical source.
Quantum dots are similar to OLED materials in that they can be made to ‘luminesce’ when stimulated by an electrical voltage, without the necessity of being ‘pumped’  by a light source.  In such a circumstance they produce the same narrow band color that they would in an optically stimulated situation, creating the ability for an RGB display.  That said, just as it was difficult for researchers to come up with a mechanism (stack) for OLED materials that could produce stability and consistency over the life of the device, it is the same for quantum dot EL materials, and such a device continues to be researched by a number of companies and educational institutions across the globe.
When it comes to making quantum dots for EL (Electro-luminescence) applications there are different challenges than those facing engineers designing materials for light-pumped applications.  In order to produce an efficient QD EL material, large numbers of QDs must be squeezed into a small space, which makes their shape, a result of the ‘shell’ that is used to protect the quantum dot materials, a focus point.  As ‘dots’ would imply spherical partials, that has been the typical shape for quantum dots but some have found a way to create a cube shell, which allows for more stable and more easily packed QDEL materials.
But there are still obstacles to overcome for EL QDs, and that tends to come down to the balance between  material efficiency, the ability to convert as much of the electrical energy put into the material to light, and the lifetime of the material itself.  Again similar to OLED materials, there is a balance with each new Quantum Dot structure that shows the relationship between applying additional voltage and the light output of the material.  At a certain point, increasing the voltage produces little or no additional light, making the device actually less efficient, while also reducing the lifetime of the material, so QD EL developers are always looking toward developing new QD materials and structures that  have a high efficiency and a long lifetime..
Thus far such materials are still in development, although red QD EL materials that have a lifetime and efficiency that can meet commercial specifications are becoming available from industry leader Nanosys (pvt), with a full stack (RGB) potentially available in 2024 and commercial production in 2025.  While there are certainly a number of obstacles that need to be overcome before such materials can compete with other display modes, the progress seen in developing QD EL materials over the last few years leads us to believe that quantum dot EL materials will find a place in the display world alongside quantum dot applications used today, and can present another way in which displays might improve and become even more pervasive than today.

Yesterday we spent some time breaking out a bit of detail as to the Samsung Display QD/OLED project and today we follow that up with a bit more discussion about quantum dots.. But before we delve into the applications for quantum dots, there is the question of the market for these nanostructures, and as with many technologies, there are discrepancies and disagreements as to the size of the market.  A quick look at some of the market estimates from industry reports shows a disagreement on market growth, likely based on the problem of inclusion that plagues much industry research.  While the past year estimates are fairly similar, future expectations are considerably varied among the more publicize estimates.  Rather than deal with the inconsistencies of such market data, which can include the use of quantum dots in medical and laser applications, our focus is on the use of quantum dots in consumer electronics.

​The primary current application for quantum dots in the CE space is for QD Enhancing Film, a sheet consisting of top and bottom polyethylene films (PET) that act as barriers and a layer of a polymer that contains a suspension of quantum dots.  The sheet is placed between the backlight and the liquid crystal system in an LCD display as an add-in, or can be molded into a replacement for the display’s light guide or diffuser, a translucent sheet that helps to evenly spread the white light from the backlight across the entire display.   While LEDs are used in most LCD display backlights the white light they produce contains a broad spectrum of colors. 
In displays without quantum dots, after the light passes through the liquid crystal, it reaches a color filter that is composed of red, green, and blue dots made of phosphors, materials that glow (luminescence) when exposed to radiant energy.  These phosphors eliminate much of the light energy contained in the white light in order to narrow the color to one of the red, green, or blue components that make up a display pixel.  For example, while a red phosphor dot emits red light, it blocks all other colors and therefore reduces the amount of light energy reaching the user.  Phosphors also have other limitations in that they are not very precise in terms of the light they let through, and with the broad spectrum of light coming from the LED backlight, a red phosphor might also allow some reddish orange or bluish red light to pass.
By inserting the quantum dot film before the light reaches the color filter, the dots can take the white light and ‘convert’ much of the broad color components, passing on a more pure red, green and blue to the phosphors, which then would be blocking less color energy.  As an alternative, instead of a white LED backlight, a blue LED backlight can be used, with red and green quantum dots converting 2/3 of the light to those colors and letting the blue light pass through to the color filter, again ‘purifying’ the colors before they reach the color filter, with both alternatives producing more vibrant colors without the high cost of more ‘precise’ phosphors. 
As we covered the use of quantum dots in Samsung Display’s new QD/OLED TV display system, we look a bit further out on the quantum dot timeline, with a focus on Micro-LEDs.  Not to be confused with Mini-LEDs, which are small but relatively easily produced LEDs, Micro-LEDs are generally under 100µm (0.004”) and are produced using typical MOCVD processes, however due to their size, transferring the requisite number of Micro-LEDs from a production wafer to a display substrate can be a monumental task, given that a 4K display would require 8.29m such Micro-LEDs of each of three colors, for a total of 24.88m Micro-LEDs, each having to be removed from the production wafer and placed on the display substrate to precisely match the driving circuitry.  As we have discussed previously, the transfer times involved, even using specially designed mass transfer tools, is quite long and therefore expensive.
That said there is a bigger problem for Micro-LEDs.  As each of the three color LEDs (RGB) are produced on their own wafers, there tends to be an interim step where each color’s LED die are removed from the production wafer and placed on a temporary substrate in order to be arranged in RGB sequence.  Once all three color Micro-LEDs have been placed on the temporary substrate in the correct order, they are again moved in sequence to the display substrate, further adding to TAC time and cost.  In order to eliminate this interim step, quantum dots can be used to simplify the transfer process.  In such a case only one color Micro-LED is needed, typically blue, which are moved directly from the production wafer to the display substrate, covering the entire display.  Red and green quantum dots are then applied to 2/3 of the blue Micro-LEDs, converting their light from blue to green and red, and eliminating the need for three separate Micro-LED production wafers.
This concept also helps to solve another problem facing Micro-LEDs, which is one of consistency.  When LEDs are produced there are both variations in light output and color, which tend to get worse as the size of the LED gets smaller. The potential solution is to test each Micro-LED, measuring luminance and color, and creating a ‘wafer map’ that tells the transfer tool to skip those that don’t meet minimum specifications, but even with this time consuming testing and mapping step, there are still significant variations across the wafer that would affect the final product.  Quantum dots can be ‘pumped’ by a relatively broad light spectrum, meaning that the variations in blue color that might occur during Micro-LED production, will not affect the ability of the red and green quantum dots to shift the blue to those primaries, avoiding the necessity of creating a ‘quality’ map, only looking for those Micro-LEDs that don’t work at all, creating a higher quality Micro-LED display than might be created using red, green, and blue Micro-LEDs and no QDs. 
By using quantum dots to color convert a single color Micro-LED display, a number of processes can be eliminated or simplified, reducing production time and cost.  While such a display system would not be purely RGB Micro-LED, using quantum dots would make the production of small pitch Micro-LED displays a far more feasible task in a mass production environment, and while there are still many production problems that need to be solved before Micro-LED displays can be mass produced at prices that are within the budget of most consumers, the use of QDs would eliminate a number of potentially large bottlenecks and push forward the Micro-LED timeline.  More tomorrow.

Over the last few years quantum dots have become a significant part of display infrastructure and have been one of two factors that have led to the ability of LCD technology to extend its dominance over newer display modes.  The addition of quantum dots to LCD displays, particularly in the TV space, has increased specifications for such displays, at a relatively low cost both from a product and manufacturing standpoint, and has given display brands a new product tier and substantial product differentiation. 
That said, we are in unparalleled times in the display industry, with a number of new display technologies surfacing that are all vying for a dominant place in the display world.  Mini-LED based displays, essentially a typical LCD display with an LED backlight on steroids, is the ‘other’ of the two technologies that has extended the life of LCD technology by improving this older technology’s contrast (The difference between pure black and pure white), a weakness that makes LCD technology less comparable to newer self-emitting technologies such as OLED.  
OLED has gone from a novelty in 2013 to the mainstay of small panel displays and while still a niche product in the TV space (<5% of total TV unit volume), it is a key technology in the lucrative premium display market.  As a self-emissive display mode, RGB OLED allows for ultimate control over each sub-pixel, generating almost infinite contrast, but large panel OLED displays are subject to two basic limitations, the first being an inability to manufacture TV size RGB OLED displays, and second, limitations on the brightness of the display.  OLED TVs use a combination of yellow/green and blue OLED emitters to create a white light that is made up of red, green, and blue light components, but in order to create the three colors necessary for an RGB display that white light must pass through a color filter, essentially a sheet of red, green, and blue dots.  Each dot will filter out two colors (for example a ‘blue’ dot will filter out red and green, while a red dot will filter out blue and green) which reduces the amount of light that is generated by the device.
OLED materials continue to improve and improvements in light extraction materials can also help to increase WOLED light output, but Samsung Display (pvt), the leader in small panel OLED, has been developing another approach that combines the properties of self-emitting OLED materials and those of quantum dots.  Yesterday Sony (SNE) announced that it would be releasing a 4K TV (Bravia XR A95K) later this year that is based on a QD/OLED panel produced by SDC, however while this is a major step for SDC, missing from the show was an announcement from parent Samsung Electronics (005930.KS) that it would also be releasing a QD/OLED TV.  While we expect that this omission was more of a tactical issue than a technology related one, Samsung’s approval and purchase of such panels are an absolute necessity for SDC, who must make the decision as to whether to expand QD/OLED production, which is currently capped at a maximum of 30,000 sheets/month. 
Without this additional potential demand SDC has little or no large panel TV display product, leaving Samsung Electronics to buy all of its TV panels from competitors and leaving SDC only able to compete in the small panel market, but Samsung Electronics must also consider where a QD/OLED TV might fit into their TV line , which already consists of pure LCD TVs at the low end, quantum dot enhanced LCD TVs at the mid-tier, quantum dot LCD+Mini-LED TVs at the top tier, and Micro-LED TVs at the ultra-high premium level. 
Rumors that Samsung is considering buying WOLED panels from LG Display (LPL) add another potential TV price class, so QD/OLED must find a place in what is a rather complex TV line-up at Samsung, and the marketing of each category is carefully considered by Samsung, who is the leader in the TV set space.  We expect Samsung Electronics to offer one or both OLED types, potentially using WOLED as a low-end OLED offering and QD/OLED as a high end OLED offering, but much will depend on SDC’s ability to keep the cost of QD/OLED panels in a range that allows Samsung these options, and with true mass production just beginning, it is likely that the focus at SDC is resolving potential yield issues rather than refining production costs.  Given the number of moving parts in such product decisions, while we were a bit surprised that Samsung did not make a specific announcement, we expect it will happen this year.
 

Since Quantum Dots are a current topic of conversations (see above), we thought it helpful to update readers on the current state of the QD space relative to display.  Quantum Dots themselves are nano-structures that are typically composed of a core material and a shell.  What makes quantum dots interesting is they are the shape-shifters of the display space, well maybe not shape-shifter but color shifter.  By stimulating a quantum dot, either optically or electrically, the quantum dot will emit light.  In the case of QDs, the actual size of the QD will determine the color that it emits, with the largest QDs emitting red and the smallest blue, so by controlling the size of the dots during production, they can be tailored to emit specific colors. 
A secondary characteristic of quantum dots is that they produce ‘precise’ colors, essentially colors that produce light at narrow wavelengths, under 50nm wide in most cases, as opposed to OLED materials that produce similar peaks but broader bases, giving display designers the ability to tailor the color balance to very tight specifications.

A 3rd characteristic of quantum dots is that when they are used to ‘color convert’ there is minimal loss of energy compared to color filters, which reduce light output by as much as 66%.  This means that when a quantum dot is ‘pumped’ (stimulated to emit light) by a light source, much of that light is converted rather than blocked, resulting in a brighter and more color saturated display.  This is theory behind Samsung Display’s QD/OLED display panels mentioned above.  In these large panels, a layer or multiple layers of OLED material, typically blue or blue and green, are spread across a substrate while red and green quantum dots are patterned above the OLED material.  In the case where the OLED material emits blue light, every third space in the quantum dot patterning is left open to allow blue light from the OLED emitter to pass through, while the red and green quantum dots convert the blue light to red and green.
There will be many variants on the structure of such panels but the theory is that the blue OLED light ‘pumps’ the quantum dots to emit their respective colors, creating a large panel RGB display without the deposition limitations that keep RGB OLED from being used for OLED TVs.  In the case of SDC’s QD/OLED display, the quantum dots are patterned using an ink jet printer, with the dots being dissolved in a solvent along with wetting agents.  This allows the entire substrate to be patterned without the metal masks used in small panel RGB OLED production and is extremely efficient in the use of materials., while able to create dots at intervals down to 2um, meaning there are few patterning limitations as to display resolution.
All in, the result should be a brighter overall panel that retains the high contrast of a self-emissive display and the color purity that quantum dots provide, however while this sounds relatively easy, the engineering behind such a device is complex.  The TFT that drive the OLED material to emit light is different than what is typically used for LTPS or LTPO backplanes used for LCD and OLED displays, so the design of the backplane  for QD/OLED was a daunting task, and while ink jet printing has been used to encapsulate OLED materials, patterning at such tight tolerances required a substantial improvement in IJP tools and  considerable research in QD ink composition, which will continue as the materials and process move into mass production. 
That said, after the initial release of Sony’s QD/OLED TV and the potential Samsung set, the question will be whether the public will see enough of a difference in the display to rationalize what will likely be a higher cost relative to WOLED.  Initial reports from some trusted sources who have seen physical demos are quite favorable, however all the positive reviews in the world are secondary to what the buyer sees when walking into  a store, and the answer to those questions will likely not be answered until later this year.  There will likely be strong pre-order sentiment from sagacious technocrats, but rank and file buyers are needed to sell enough units to justify the production expansion necessary to establish the technology as a potential display modality and to support the continuation of the R&D necessary to reduce costs and make material and manufacturing improvements.  More on QDs tomorrow.

will have to shell out more if you still want to surprise the wife with a new high-end Samsung TV.  With only two of the 35 Mini-LED/QD or QD only sets not at their lowest price (94.3%) last time we checked (11/26) Samsung has since boosted prices on many, leaving only 20 (57.1%) still at their all-time lowest price.  Samsung did not change the set prices on any of the six 8K Mini-LED TV sets, but made some serious changes in pricing on the 4K Mini-LED/QD sets, where prices increased between 7.7% and 35%, with only the 98” set remaining flat at $15,000 and a 43” Mini-LED/QD model seeing a 7.7% price drop, the only drop in the group.  The 18 QD only sets saw three price decreases (55” and smaller sets) ranging from -5.9% to -10.0%, but the rest saw price increases ranging from flat to an astounding 58.8% increase, with the average increase for QD only sets being 6.2% and the average increase across the entire Mini-LED/QD and QD only line 7.3%.
While Samsung is advertising these sets under the title of “Don’t miss Black Friday in winter pricing”, prices have increased over the last few weeks as a host of supply chain issues and COVID-19 take their toll on in-store sales.  Of the 35 Samsung TVs listed on the Best Buy (BBY) site, 23 were in stock (65.7%) and across all TV brands carried by Best Buy, 75.9% were in stock, indicating that little has changed across the TV supply chain.  While we expect few discounts between now and the end of the year, New Year sales will likely occur, at least to some degree, and with many new models from TV brands being introduced at CES in January, brands will start to focus on reducing 2021 inventory in anticipation of building 2022 model stocks, so 2021 models will likely see another round of discounts before the new models become available. 
At CES Samsung is expected to show the first iteration of its QD/OLED TV that is based on multiple OLED layers and quantum dots that convert the OLED light into RGB pixels.  While pricing will certainly be an issue given the new technology and minimal production, we expect the product to be of high quality and a step ahead of what is currently available.  While Samsung Electronics has a wide variety of TV technologies for consumers to choose from, and might be offering WOLED TVs at some point this year, the new QD/OLED product is more important to Samsung Display (pvt) who has ended most of its large panel LCD TV production and needs a product that can fill that gap over the next two years.  While SDC dominates the small panel OLED market, they have a need for a blockbuster large panel product that they can sell to parent Samsung Electronics and Sony (SNE) with enough success to justify capacity expansion.  Without that type of successful product, they will remain out of much of the TV panel market.

​Samsung (005730.KS) continues to play with its Mini-LED/QD TV pricing, almost on a weekly basis, and while two of the 36 sets in the 2021 Mini-LED/QD or QD only line-up are at their highest price point since release, 23 are at their lowest price point, with all 8K Mini-LED/QD sets at their lowest price points.  The biggest changes from our last pricing (2 weeks ago) show up in the same 8K Mini-LED/QD group, where the average price drop (wk/wk) is $400, with those sets down 25.3% from their original price on average, however as the largest size (85”) set has changed little in price over the last month, the two other sizes are down 29.3% from their original price.
A number of the QD only sets also moved considerably over the last two weeks, with one model (75QA) dropping from $2,700 to $1,900, an almost 30% discount, while most other 4K Mini-LED/QD and QD only sets are down from their original prices between the high teens and low 20% range.  While all TV brands play with TV pricing, Samsung seems to be far more willing to offer discounts on this year’s line, particularly with Mini-LED/QD sets.  While taking advantage of a particular bi-weekly change might get you some short-term savings, the trend has been downward, which will likely continue for the rest of the year.

Quantum Dots have been around for many years, but right around the time that commercial OLED TVs were being shown at CES for the first time, quantum dot films began to appear in the vocabulary of display manufacturers.  These semiconductor crystals, which vary in size from 2um to 10um, have the unique property of being able to convert light of one color (frequency) into another, with that ability being determined by the QD size, with the larger dots converting to red, intermediate size converting to green, and the smallest sizes converting to blue. 
This means by ‘tuning’ the size of the QD crystals when they are synthesized, they can be used to convert light of a particular frequency (color) to another color.  This differs from phosphors, which typically ‘block’ the light of other colors, with a red phosphor removing the blue and green from a white light and letting only the red light pass.  Phosphors therefore reduce the light energy output significantly, while quantum dots ‘shift’ the energy rather than reduce it.
Quantum dots also have other beneficial characteristics, particularly their ‘narrow’ output relative to other materials, which gives them the ability to generate ‘pure’ colors that allow displays to more precisely control the colors that are produced.  As quantum dots are ‘stimulated’ by light, they are ideal for QDEF (quantum dot enhancement films) or QDOG (quantum dot on glass) systems that are the basis for many high-end TVs sold today, and have applications where they can replace typical phosphor based color filters in large size LCD and OLED displays, or can be used to convert a single color backlight into an RGB display at a low cost.
But quantum dots have another characteristic that makes them valuable in the display space, and that is not only can they convert the frequency of light that stimulates the QDs, but by applying an electrical charge to the QDs, they can produce light on their own.  This self-emissive property is similar to the plasma displays of years ago, where a gas was electrically stimulated to produce a colored dot, or OLED materials that have the same basic property.
Producing quantum dots is a chemical process that must be carefully controlled but is certainly viable for mass production and the move away from cadmium-based quantum dots has reduced or eliminated any question of safety for consumers, with the dots being combined in films or deposited directly on light guides in TV displays.  But to use quantum dots effectively for more sophisticated applications, they face the same issues as OLED materials, that of patterning, or precisely placing the dots on the corresponding points in the TFT (thin film transistor) circuitry that controls them.  In a 4K display this means over 24m quantum dots have to be correctly placed and in an 8K display just under 100m dots ‘spots’ must align with the TFT electronics.
Small OLED displays are able to use FMM (fine metal masks) to precisely place OLED materials when creating and RGB display, but those masks do not scale to the sizes needed for large OLED TVs, which uses two OLED materials that are coated across the entire display to produce white light, which is then converted to the three primary colors by a color filter.  As noted above, the color filter is ‘subtractive’ and reduces the light output of the display, which makes it more difficult for large OLED displays to compete with large LCD displays which tend to be brighter, so the idea of using quantum dots as self-emitting materials would offer a solution to that problem only if the QDs can be patterned across such large displays.
Ink-jet printing is one way that has been tried for patterning self-emissive materials, both OLEDs and quantum dots, but IJP involves dissolving the materials in solvents so they can pass through the ink-jet heads.  This can affect the materials, requires ‘curing’ before adjacent materials are deposited, and can add variability to the ink-jet droplets themselves.  While IJP is certainly a developing technology that is already used to a degree in the display space, a simpler and less ‘invasive’ process would likely be necessary if self-emissive quantum dots were to surface as a viable commercial display process.
Much research is being conducted on moving quantum dots from ‘converters’ to emitters’, but we have noticed that a group of engineers at a TCL (000100.CH)/Chinastar (pvt) Innovation center have come up with a novel approach to patterning quantum dots that seems to hold promise as a potentially commercial process.  The concept uses a process called electrophoretic deposition, which moves particles that are charged to an oppositely charged electrode.  Quantum dots can be charged by attaching positive or negative ions to the bonds that attach to the QD core and placing an oppositely charged material in the solution will attract the dots to that material, but that only gets them there en masse.
The trick that these researchers came up with is to use photolithography to produce an electrode that is patterned, and will only attract QDs where the pattern exists, similar to the way photolithography is used to produce the circuitry that is the basis for the millions of transistors that appear on semiconductor devices.  In the same way, second and third electrode pattern can also be created that would only attract QDs to those locations when turned on, so by charging each electrode only when it is in the proper ‘color’ solution, a complete RGB QD pattern can be created on large substrates, with the thickness of the material controllable by varying the time and strength of the electrical field.  In some cases the QDs might be stacked, which would entail simpler patterning and the same three dip process and the process is not limited to rigid substrates opening up the process to flexible and 3D structures.  The process (in the lab) took less than a minute for each color with about 20mins drying time for each.
While we don’t often cite lab technology, given the difficulty in transferring much of this kind of work into scalable production, much of this process uses existing technology that is available to display producers or is already part of their process, so it does have some relevance to a working solution that could one day be profitable.  The characteristics of quantum dots, particularly their inorganic nature (core) and their color purity make them viable candidates for self-emissive displays and such a more practical process could legitimize the continuing R&D into the development of a realistic Self-emissive QD product timeline.[1]


[1] Zhao, Jinyang. “Large-Area Patterning of Full-Color Quantum Dot Arrays beyond 1000 Pixels per Inch by Selective Electrophoretic Deposition.” Nature Communications.