Size dependence of photovoltaic properties and surface states modulation in ZnO nanowire/poly(3-hexylthiophene) hybrid nanostructures

Abstract

An appropriate diameter and wire-to-wire distance is critical for optimizing the performance of hybrid inorganic/organic photovoltaic devices. For a deep understanding of their influences on such hybrid structures, the well-ordered ZnO nanowires with different diameters are fabricated by the versatile hydrothermal growth. The dependence of the photovoltaic performance on the surface states, wire diameter and wire-to-wire distance is investigated. We demonstrate that the pristine thick ZnO nanowires film possess a higher surface photovoltage (SPV) response than the thin one. This is mainly due to the influence of surface states on the thin ZnO nanowires, which can capture the photo-generated carriers. When the two kinds of ZnO nanowires are fabricated into a hybrid inorganic/organic structure, the thin ZnO nanowires/poly(3-hexylthiophene) hybrid film has a higher SPV response than the thick one, which is contrary to the pristine ZnO nanowires. This is benefited from the smaller diameter and wire-to-wire distance of the thin ZnO nanowires owned. The crystallinity, wire diameter and wire-to-wire distance have the crucial influence on the final photovoltaic performance. The results shown here give us insights toward designing efficient hybrid photovoltaic devices.