A 3.4‐in. Flexible High‐Resolution Full‐Color Top‐Emitting AMOLED Display

Abstract

In this paper, we report a 3.4‐inch flexible top‐emitting AMOLED display with remarkably high resolution using oxide TFTs. Our transfer technology has an advantage of fabricating high‐performance TFTs and a high‐resolution AMOLED Display on a flexible substrate.

Metal oxide semiconductor thin-film transistors for flexible electronics

“…162 In alternative to flexible substrates manufactured independently from the TFTs, it is also possible to create the flexible substrate by covering a host substrate with a polymer using either evaporation, 80,81,141 spin, slot or blade coating techniques. 23,39,133,135,137,142,144,147,155,161,164,179 The advantages of these fabrication techniques based on a rigid support are a high compatibility with the standard fabrication processes on Si or glass wafers, a reduction of the expansion of the substrate during the manufacturing process, as well as the possibility to realize devices on very thin (%1 lm) substrates. After the TFT fabrication is completed, the flexible foils or thin deposited polymer layers carrying the devices can be separated from the rigid support using: (1) mechanical peeling, 38,142,155,158,161,164,166,168,179 (2) a low adhesion releasing layer, 133,144 (3) a supporting laser, 137 or (4) a sacrificial layer between the host carrier and the polymer.…”

“…144 To increase the mechanical stability or to realize electronic devices on alternative surfaces, thin flexible substrates have also been transferred and attached to a new carrier like PI or organic tissues. 38,39,78,80,81,141 Finally, it is also possible to fabricate TFTs directly on a rigid carrier coated with a sacrificial layer and subsequently transfer only the devices onto a flexible substrate. 38,78,82,205 In addition to the different handling possibilities, the substrate preparation typically includes a heat treatment step prior to the device fabrication itself.…”

“…Flexible n-type vacuum-processed metal oxide semiconductor TFTs, especially based on IGZO active layers, bent to different radii have been characterized by many research groups. 39,80,96,[132][133][134][135]139,[152][153][154][155][156][157][158][159][160][161][179][180][181]184,204,208,215 As illustrated in Fig. 22(a), mechanical bending tests are, in general, performed by winding the flexible TFTs substrate around cylindrical rods.…”

“…top-emitting AMOLED display yielding 326 pixels per inch (ppi) resolution and consuming 570 mW power. 39 Additionally, the display by Chida et al is operational after 1000 bending cycles at 5 mm bending radius. One year later, Genoe et al proposed the use of a digital pulse width modulation (PWM) to drive a flexible topemitting AMOLED display (0.54-in., 320 ppi).…”

“…36 Furthermore, metal oxide semiconductor TFTs show a larger resistance to mechanical strain if compared with LTPS devices. 30 This is why metal oxide semiconductors are considered the most prominent candidate for next-generation flexible high-resolution active matrix organic light emitting diode (AMOLED) display backplanes, [38][39][40][41] as well as the most suitable technology to fuel the realization of tomorrow's ubiquitous electronics. Main aim of this review is to report the recent advances obtained in the field of flexible metal oxide semiconductor TFTs: from single devices (Sections II and III), large-area circuits (Section IV) up to entirely integrated systems (Section V).…”