Rapid UV-A photo detection using a BTBT organic thin-film transistor enhanced by a 1,5-dichloro-9,10-dintiro-anthracene acceptor

A UV-A sensitive phototransistor was demonstrated using an organic semiconductor 2,7-dipentyl[1] benzothieno[3,2- b][1] benzothiophene (C5-BTBT) and a strong electron acceptor 1,5-dichloro-9,10-dintiro-anthracene (2Cl-2NO(2)-Anth) which is not photo-isomerizable. At 0 gate bias the photo-responsivity of the device begins to saturate at an incident power P-inc = 1 mW/cm(2), where a photocurrent-to-dark current ratio (P) of P > 10(5) is observed with a photoresponsivity of 9 A/W. The photoresponsivity was increased with the decrease of P-inc, reaching 40 A/W at a P-inc = 0.0427 mW/cm(2). A persistent photocurrent with a P > 10(5) was observed for more than 2 h, demonstrating the potential use for rewritable photo memory. By applying a gate voltage program consisting of a reset pulse of -90 V every 2nd data point, the device can perform as a UV sensor or switch at the timescale of 600 ms. (C) 2016 Elsevier B.V. All rights reserved.