Apple uses OLED displays in the Apple Watch.
Apple has a bunch of constraints which made the adoption of OLED for phones difficult.
There has been an ongoing issue with the color accuracy of OLEDs which would have meant a backward step for the the company. Apple has has been improving color accuracy and gamut year on year, OLEDs until recently, were often overly saturated. Only in the last year or so have the displays gotten good enough.
There is an issue with supply volume. Simply obtaining that quantity of screens would have required a significant shift in production. It’s one thing to make a few million handsets, but when Apple orders a fifty million displays, that sort of change requires more than a year to make happen. Entire plants have to be built to accommodate that size of order.
Wang Jyh-chau, CEO of LCD maker Innolux, notes that “OLED cannot replace LCD in terms of performance-cost ratio and reliability,”
OLED technology is relatively newer tech and has multiple flaws. Brightness is lower as the backlight on the led display is way more powerful than the pixels on the oled. Oled also has problems with over saturation
So here comes the idea of microLED that have not been exploited in tech circle and this one is highly functional than OLED technology!
According to Wikipedia, microLED is defined as
microLED, also known as micro-LED, mLED or µLED, is an emerging flat panel display technology. As the name implies, mLED displays consist of arrays of microscopic LEDsforming the individual pixel elements. Compared to the widespread LCD technology, mLED displays offer far greater contrast, much faster response times, and would use less energy.
Along with OLEDs, mLEDs are primarily aimed at small, low-energy devices such as smartwatches and smartphones. OLED and mLED both offer greatly reduced energy requirements compared to conventional LCD systems. Unlike OLED, mLED is based on conventional GaN LED technology, which offers far higher total brightness than OLED products, as much as 30 times, as well as higher efficiency in terms of lux/W. It also does not suffer from the shorter lifetimes of OLED, although the multi-year lifespan of modern OLEDs has mitigated this issue in most roles.
As of 2016, mLED displays have not been mass produced or commercialized.