Near-UV Irradiation Effects on Pentacene-Based Organic Thin Film Transistors

Abstract

We irradiated Organic Thin-Film Transistors using light sources with peak wavelength in the near-UV spectrum. Organic Thin-Film Transistors have been found very sensitive to near UV rays. Irradiation generates negative trapped charge due to photogeneration, as well as neutral defects, which degrade the mobility and transconductance. We observed noticeable degradation even with 400-nm wavelength, which lies between visible and UV-light. Stronger variations were observed with the shortest wavelength, with a transconductance drop of 85% after 33000-s irradiation with 310 nm UV. We found that the mobility degradation is permanent after storing the devices in vacuum at least for 50 days

Enhanced permanent degradation of organic TFT under electrical stress and visible light exposure

“…It is well known that either light or bias induce charge trapping [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41], and this is confirmed by the experimental results plotted on Fig. 5.…”

“…Very small variations occur on the reference device. Any changes arise from the intrinsic aging, due to air and moisture exposure, and from the effects of measurements on the characteristic themselves, as we discussed in [39,40]. When bias is applied (Fig.…”

“…Because stress and/or light generate a large amount of charge unstably trapped in oxide and/or pentacene [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41], we repeated the characterization 24 and 48 h after the procedure was finished. We verified that after 24 h, the trapped charge is almost completely neutralized.…”

“…Beside permanent degradation due to oxygen and water contamination, TFTs are well known to suffer from charge trapping, if a high enough prolonged bias is applied [24][25][26][27][28][29][30][31][32][33]. Moreover, bias effects are exacerbated by light [34][35][36][37][38][39][40][41]. In [39,40] we demonstrated that permanent degradation may occur also in unbiased OTFT devices exposed to light sources with high enough photon energy, e.g.…”

“…Moreover, bias effects are exacerbated by light [34][35][36][37][38][39][40][41]. In [39,40] we demonstrated that permanent degradation may occur also in unbiased OTFT devices exposed to light sources with high enough photon energy, e.g. UV light.…”