Flexible organic N-channel phototransistor and integrated logic devices

Abstract

A flexible organic field-effect transistor (OFET) and flexible phototransistor have been fabricated using self-assembled single crystals of a small molecule, viz, N,N’-dioctyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C8). The solution processed single crystals of PTCDI-C8 with strong molecular ordering showed excellent OFET performances having mobility μ∼0.2cm2/Vs. The absence of grain boundaries, traps and intrinsically defect-free nature of the single crystals contributed to the improved device performances in PTCDI-C8 crystalline OFET. The device exhibited high sensitivity to photo-illumination with photoresponsivity value upto Ca. 3A/W and photo to dark current ratio ∼103. Both the transistor and photosensing characteristics of the OFET device were retained even under extreme bending of the flexible substrate, exhibiting robust mechanical flexibility of the OPT. To realize OFET based electro-optical logic circuits, we have suitably integrated the photo signal and electrical signal and demonstrated that binary NOT and OR operations could be performed on the OFET device with light as one of the input signal. The large area deposition of self-assembled organic single crystals with multifunctional activity, such as, photosensing with switching, signal amplification, and electro-optical logic operation opens up immense possibilities for flexible organic logic device and promises great potential for future low-cost plastic optoelectronic applications.