A new kind of backplane TFT is rising on the horizon which the Apple iPhone may adopt in the long term, according to experts in the display industry.
Power consumption is always a critical element in the smartphone, with the central processing unit (CPU) and display screen the most two power-hungry components in the device. In helping prolong the overall battery life of a smartphone while also reducing its power consumption, an important element is the smartphone display, especially for emissive types like AMOLED, or active-matrix organic light-emitting display.
At present, mobile AMOLEDs have adopted low-temperature polysilicon thin-film transistor (LTPS TFT) as the standard backplane, whether in rigid OLEDs with a glass substrate or in flexible OLEDs with a polyimide substrate. This is because of good electron mobility, which drives OLED circuitry and materials to achieve high pixel densities.
However, a new kind of backplane TFT - The the so-called LTPO, or low-temperature polycrystalline oxide - is gaining interest.
The LTPO TFT was first mass-produced and applied to the display of the Apple Watch Series 4 OLED display released last September.
Speaking at the 'Display Tech Salon' hosted by Korea Display Industry Association held in Gangnam-gu, Seoul on the 21st, Park Ki-chan, Professor at Konkuk University, said that using LTPO TFTs in Apple's smartwatch series 4, the driving power was reduced by 1/3, resulting in a total power consumption reduction of 40%.
However, while smartwatches display information on a black background, iPhones use most of the screen, resulting in lower overall loewr power consumption gains. "Emission power accounts for about 80% of smartphone display power. Applying LTPO TFT to an iPhone screen would result in a total power reduction of about 13% even if the required driving power is reduced to one third," Park said.
According to IHS Markit, the oxide TFT structure can reduce the current power-leakage problem of LTPS.
"I think Apple has plans to apply LTPO to the iPhone in 2021," said Kang Min-soo, a researcher at IHS Markit.
Apple has applied for three important patents on LTPO. The first occurred in 2014 with the patent title "Organic light-emitting diode displays with semiconducting-oxide and silicon thin-film transistors." The second, in 2015, bore the patent title of "Displays with silicon and semiconducting oxide thin-film transistors." A third took place this year, with the title "Methods of protecting semiconductor oxide channel in hybrid TFT process flow."