Ultra-wide bandgap organic acceptor material and its application in organic UV photodetector

Abstract

Two fluorene derivatives, 2-(1,1′:3′,1″-triphenyl-5′-yl)-9,9-diphenyl-9H-fluorene (TPF) and (9,9-diphenyl-9H-fluoren-2-yl)diphenylphosphine oxide (DFPPO) with wide bandgap and good thermal stability were synthesized. The electron mobility of DFPPO is 5 times higher than that of TPF because of the introduction of the electron-withdrawing diphenylphosphine oxide group. The planar heterojunction organic ultraviolet photodetectors (UVDs) were fabricated by applying TPF or DFPPO as electron acceptor, 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) as donor. The UVDs with structure of ITO/PEDOT:PSS/C8-BTBT/DFPPO/LiF/Al presented higher ultraviolet response compared to the TPF based counterpart. Corresponding dark to light current ratio and higher sensitivity is about 179 and 0.69mA/W under illumination of 1mW/cm2 365nm UV light and bias of −0.5V.