Electron Trapping Group Induced Enhancement in Photoresponses of Organic Field-Effect Transistors

Abstract

The dielectric–semiconductor interface plays a critical role in determining the performance of organic field-effect transistors (OFETs) as the first few layers of the semiconductor actively participate in charge transportation. Several methods, such as self-assembled monolayer deposition, plasma treatment, and UV–ozone (UVO) treatment, have been explored to modify the dielectric surface and enhance the OFET performance. Although the effect of UVO treatment on OFET characteristics has been investigated in past few reports, the influence on photoresponses still remains unexplored. This study proposes an efficient approach to enhance photoresponses in dinaphtho­[2,3-b:2′,3′-f]­thieno­[3,2-b]­thiophene (DNTT)-based OFETs through UVO treatment of the poly­(methyl methacrylate) (PMMA) surface. UVO-treated devices exhibit notable enhancement in drain-to-source current (I D) under dark conditions and improved photoresponses under white light illumination. The photosensitivity increases from 2.26 × 105 to 6.65 × 106, whereas detectivity improves from 1.09 × 109 to 1.98 × 1014 Jones after 10 min of UVO treatment. Furthermore, the responsivity increases from 1.48 × 103 to 4.33 × 105 A/W at a low intensity of 5 μW/cm2. The decrease in the water contact angle after UVO treatment indicates higher hydrophilicity of the PMMA surface, which in turn leads to better growth of DNTT molecules, further confirmed by atomic force microscopy (AFM) and grazing incidence X-ray diffraction (GIXRD). X-ray photoelectron spectroscopy (XPS) analysis indicates the generation of polar functional groups on the PMMA surface serving as electron acceptor sites. These sites enhance the effective hole concentration by trapping photoinduced electrons at the dielectric–semiconductor interface, resulting in improved photoresponses. Our findings, thus, demonstrate the potential of UVO treatment as a facile yet efficient route to enhance the photosensing performance of OFETs.