It is important to note that an IGZO display is not a type of electronic display technology. It specifically represents a display panel that uses a backplane thin-film transistor or TFT made of indium gallium zinc oxide or IGZO semiconductor material. This means that it is compatible with different LCD technologies such as twisted nematic or TN LCD, virtual alignment or VA LCD, and in-plane switching or IPS LCD technologies.
The same material can also be used in other display technologies such as OLED or AMOLED, MicroLED, and quantum dot display technology, and complementary display technologies such as the Mini-LED backlighting scheme. Nevertheless, to understand further what IGZO displays are and how they work, it is important to understand its properties or characteristics, and thereby its advantages and disadvantages or benefits and limitations.
Benefits: Advantages of IGZO Display
1. Natural Transparency
A notable advantage of an IGZO-based TFT over silicon-based ones such as amorphous silicon or aSi-TF is that it allows the passage of more light. This is because the material is naturally transparent and more compact. Hence, based on this material property, one of the specific advantages of IGZO displays is their natural transparency.
This transparency translates to energy efficiency. An LCD based on an IGZO TFT uses less power than an LCD that uses an aSi-TFT due to the reduced need for backlighting intensity. An OLED panel that uses this material also has better transparency and more vibrant color reproduction than an OLED panel based on alternative TFT materials.
It is also worth mentioning that improving the transparency of thin-film transistors can improve the viewability of panels when used outdoors or under bright sunlight. This is an ideal solution to the poorer outdoor visibility of OLED panels. Transparency can also enhance aesthetic appeal because it can create a sense of depth and dimensionality.
2. Better Electron Mobility
An IGZO semiconductor has 30 to 50 times more electron mobility than amorphous silicon. This higher electron mobility corresponds to more specific benefits. For example, when it comes to design considerations, it allows the production of a smaller footprint without compromising conductivity. This is essential in developing thinner and lighter panels.
It is worth mentioning that the size of transistors affects the size of the pixel. Hence, because of its higher electron mobility, another advantage of an IGZO display over a silicon-based display is a higher density within a smaller display real estate. It is interesting to note that earlier IGZO display prototypes had crammed 498 pixels per inch within a six-inch footprint.
The backlighting in a pixel-dense silicon-based LCD panel is obstructed. This panel is rated to draw more power for more intense backlighting to compensate for this drawback. The power consumption requirement increases of an aSi-TFT LCD increases with an increase in the pixel density. This is not a problem in IGZO-based TFT LCD panels.
3. Low Current Leakage
It is also worth mentioning that IGZO has electron mobility that is almost comparable to a material called LTPS or low-temperature polysilicon. The problem with an LTPS is that it has a higher current leakage which makes it power inefficient. An amorphous silicon has a lower current leakage but it also has a lower electron mobility than IGZO and LTPS.
The low current leakage and high electron mobility of IGZO affords it a more advantageous current flow than both aSi and LTPS. This advantage means that the transistors in this TFT material do not have to be refreshed continuously while displaying a still image because it can retain the active state of its pixels longer due to its advantageous current flow.
Panels that use either aSi or LTPS need to overwrite still image data through a continuous refresh. This means that these panels can consume between 80 percent and 90 percent more power while displaying still images than panels based on IGZO. A specific IGZO display panel is more ideal for use cases that involve static images or less need for pixel refreshing.
4. Less Noise Influence
Another advantage of IGZO is less noise influence. Note that noise influence is characterized by unwanted or random variations in the brightness, color, or sharpness of the pixels on a screen. This can be a source of distraction for some users. IGZO display panels are less susceptible to this effect because indium gallium zinc oxide is an intermittent semiconductor,
Take note that the drive in a specific IGZO display does not need to be continuous. This allows touch input to be more sensitive and responsive. Furthermore, although noise is a consequence of touch-sensitive panels, the noise generated by touching a panel that uses an IGZO TFT is brief. This results in a more accurate detection of even the faintest signal.
IGZO display panels with an accurate level of touch sensitivity can pick up thinner and finer lines than non-IGZO display panels such as those that use silicon-based TFT materials. This means that writing on an IGZO using a stylus pen has a closer feel to using a pen on paper. The material can enable mimicking natural handwriting input.
Limitations: Disadvantages of IGZO Display
1. Key Material Drawbacks
It is important to underscore the fact that IGZO is a metal oxide. Indium, gallium, and zinc can form unwarranted chemicals with oxygen and other elements. This is one of the notable disadvantages of this material. The metal contacts between the source or drain electrodes and the channels can react with oxygen in the air or on the surface.
The high susceptibility to chemical reactions means that display panels that use IGZO TFT can result in internal hardware failures. Oxidation can increase the capacitance and resistance of the metal contacts. The chemical composition of the material can also change due to thermal stress, mechanical stress, and other factors such as humidity and light exposure.
Another disadvantage of IGZO comes from the lower uniformity of electron mobility when compared to aSi and LTPS. This can result in variations in product quality across similar products or batches of units. The same problem with electron mobility can also result in operation disruptions or performance inconsistencies in an individual IGZO-based product.
2. Production Challenges
There is another problem when it comes to producing and popularizing IGZO display panels. Both indium and gallium are rare-earth metals. This means that capitalizing on this material exposes manufacturers to higher costs and procurement or supply chain issues that can affect their production schedules. This can also translate to higher production costs.
Furthermore, apart from securing scarce raw materials, one of the main obstacles in producing IGZO is synthesis. Pulsed Laser Deposition or PLD is the most common synthesis method used in the industry. This lengthens production time and increases costs because it requires expensive equipment and a considerable time output to adapt to environmental conditions.
The manufacturing or production challenges mentioned above translate to another advantage of IGZO display panels. Take note that IPS LCD panels made of silicon-based TFT tend to retail between USD 200.00 and USD 1000.00. Those made of IGZO have a substantial price difference that ranges from USD 1000.00 to USD 4000.00 and above.
3. Variable Response Time
Remember that one of the advantages of IGZO display is a better response time than aSi-TFT and other silicone-based TFT displays. It is worth mentioning that LCD technologies such as TN LCD and IPS LCD inherently have slow response times when compared to emissive display technologies such as OLED. This is a disadvantage of IGZO-based LCD panels.
An OLED panel based on can still take advantage of this faster response time because this is an inherent advantage. This response time is estimated to be less than 0.2 seconds. However, when factoring in the higher cost of producing OLED panels with the higher cost of synthesizing indium gallium zinc oxide, the total production costs would shoot up.
It is worth mentioning that a slower pixel response time can create ghosting effects or motion blurs when displaying fast-moving images. This can further result in eyestrains. Manufacturers have solved this issue with LCD panels through the addition of drivers or processors. This added component also translates to an additional cost and more power draw.
Takeaway: Advantages and Disadvantages of IGZO Display
The advantages of IGZO display revolve around its physical and chemical properties that enable it to operate under lesser power requirements than its silicone-based counterparts. This same TFT material enables the production of larger panels with higher pixel density. These advantages benefit consumer electronic devices such as smartphones and portable computers.
It is also important to reiterate the fact that IGZO is not a type of display panel but a specific manufacturing configuration or a complementary display technology. This means that it can be applied to other display technologies such as twisted nematic or TN LCD and in-plane switching or IPS LCD technologies or AMOLED and MicroLED technologies.
There is also no considerable difference between an LCD or OLED based on aSi-TFT and an LCD or OLED based on IGZO in terms of overall display quality. However, as discussed above, IGZO-based display panels have considerable advantages such as substantial power saving and a smaller physical footprint without compromising pixel density and brightness.
A hybrid between IGZO and LTPS is possible. Apple has demonstrated through its Apple Watch devices that it is possible to combine silicon-based and oxide-based materials with the so-called low-temperature polycrystalline oxide or LTPO display. LTPO-based panels have become one of the features of high-end consumer electronic devices such as smartphones.