The photoresponsive current-voltage characteristics of organic thin film transistors (OTFTs) have been studied as a function of gate-bias. For the active layer of the OTFTs, soluble 1,2,4,5-tetra(5′ -hexyl- [2, 2′] terthiophenyl-5-vinyl)-benzene materials have been used, and the thickness of the active layers varied. The photosensitivity of the OTFTs was controlled through both gate-bias (Vg) and incident light power. With increasing incident light power, the photosensitivity decreased during the source-drain current actively varied with Vg [i.e., at on-state with accumulated hole channel (Vg < Vonset)], while it increased for Vg≥Vonset (at off-state without accumulated hole channel). These variations are caused by two kinds of photocurrent mechanisms: One based on the photovoltaic effect for Vg < Vonset and another based on the photoconductive effect for Vg V onset. The maximum photosensitivity of OTFTs was found to be approximately 40 times higher in the on-state than in the off-state due to the contribution of photovoltaic effect in the on-state.
Bibliographical noteFunding Information:
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (Grant No. R0A-2007-000-20053-0).
ASJC Scopus subject areas
- Physics and Astronomy(all)