Transparent Active Matrix Organic Light-Emitting Diode Displays Driven by Nanowire Transistor Circuitry

Optically transparent, mechanically flexible displays are attractive for next-generation visual technologies and portable electronics. In principle, current generation organic light-emitting diodes (OLEDs) satisfy key requirements for this application: transparency, lightweight, flexibility, and low-temperature fabrication, among current-generation electroluminescent materials, both small molecules and polymers are promising for full-color active matrix OLED (AMOLED). The fabrication of this kind of circuits also has an important challenge, the need of transparent transistor and circuit integration strategies. Consider that each pixel must have at least one switching transistor, one driver transistor, and a storage capacitor. Silicon technologies made over glass haven proven to be able to deliver the correct amount of power over AMOLED’s. However, conventional poly Si backplanes are optically opaque and not well suited for flexible displays requiring low-temperature processing and transparency. While organic thin-film transistors are compatible with low-temperature processing and some are optically transparent they have relatively low carrier mobility and typically utilize relatively long channel lengths, dictating relatively large transistor areas to provide the required drive current, this makes architectures in which the TFT area becomes comparable to that of the pixel emitter area, leading to unacceptable brightness resolution-power consumption trade-offs.

Nanowire transistors are transistors having one or more semiconductor nanowires as active channel region, potentially offer the performance required for AMOLED circuitry along with desired transparency and processing characteristics. Approaches in which NWs are synthesized on sacrificial substrates and then straightforwardly transferred to the device substrate allow the realization of high-performance channel regions without high-temperature processing. In this paper In₂O₃  nanowires were used as active channel materials, a performance-enhancing hing-k organic self-assembled nanodielectric as the gate unsulator, and ITO as the conducting gate and S-D electrodes.

The full fabrication process can be found in the papper. 

The figure shows the cross-section view of the AMOLED structure.

This figure shows the NW-AMOLED display, where clearly we can see the brightness of the display and the possibility of controlling the brightness individually.  So in general the conclusions are that it’s possible to manufacture an AMOLED based on room temperature process and highly transparent components manufactured by nanowires.  Even do there are great results, it’s necessary to improve the maximum brightness and maximum aperture ratio.

This AMOLED’s can be used for applications such as windshield displays, head mounted displays, transparent screen monitors, mobile phones, PDAs, personal computers, etc.

Source: NanoLetters 2008 Vol. 8, No. 4. 997-1004