Highly efficient ultraviolet photodetectors based onTiO2 nanocrystal–polymer composites via wet processing

Abstract

Solution-processed inorganic/organic hybrid films based on anataseTiO2 nanocrystals and poly (9,9-dihexylfluorene) (PFH) are fabricated via a simple spin-coatingmethod and characterized by atomic force microscopy, UV–vis absorption andphotoluminescence spectra. The photodetector devices are made from hybridTiO2/PFH bulkheterojunction films sandwiched between poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonate)pre-coated ITO and Al electrodes. The device characteristics, including current–voltage (I–V)curves under UV illumination, spectral response, response time and bias dependence, are studied.The photovoltaic effect is observed and the photocurrent shows an increase with increasingTiO2 content from 2.5 to 11 wt%. The high UV photo-to-dark current ratio of103, fast response time less than 200 ms and a responsivity of54.6 mA W − 1 are obtained for the hybrid photodetector. The fast photoresponse is attributed to theenhanced interfacial dissociation of excitons. The overlap of the spectral response with theUV–A range (320–400 nm) and the low-cost wet fabrication method show their potential forenvironmental and biological uses.