Effects of carrier mobility on photocurrent generation in TiO2/poly(alkylthiophene) photovoltaic devices

Abstract

In heterojunction photovoltaic devices of ITO/TiO2/poly(3-alkylthiophene)/Au, the photocurrent was characterized at different temperatures for different alkyl chain lengths and regioregularities: regiorandom, regioregular poly(3-hexylthiophene), and regioregular poly(3-dodecylthiophene). The regioregularity and alkyl chain length affected the photovoltaic characteristics due to differences in hole-carrier transportation. The drift charge mobilities of these devices were analyzed by the space-charge-limited current theory using the relation between the dark current and the bias voltage. The photocurrent in the devices based on poly(3-alkylthiophene)s decreased rapidly below the temperature at which the drift charge mobility was 10(-5) cm(2)/V (.) s.