Delft University of Technology researchers will describe a novel low-temperature method for fabricating solution-processed polysilicon thin-film transistors (TFTs) for use with a wide range of arbitrary large-area substrates, including paper. The TFTs had electron mobilities of 23.5 and 21.0 cm2/Vs (for PMOS and NMOS, respectively).
Although other solution-processed polysilicon and single-grain silicon TFTs have higher electron mobilities, they require high-temperature annealing which rules out low-cost plastic or paper substrates. Meanwhile, other TFTs made at low temperatures but from organic or metal-oxide materials have poor mobilities, only half as much as the Delft devices at best, meaning their performance is limited.
The Delft team made the devices by casting a quantity of liquid polysilane onto a substrate, and forming a thin film from it by “doctor-blading,” or skimming it with a blade. High-performance polysilicon channel regions then were formed by laser annealing, using short pulses of coherent light to selectively crystallize the disordered film. The maximum temperature required was only 150ºC, making the TFTs suitable for paper and plastic substrates such as PET and PEN.
(Paper #26.5, “Solution-Processed Poly-Si TFTs Fabricated at a Maximum Temperature of 150°C,” M. Trifunovic et al, Delft University of Technology)