Solution-processed extremely thin films of Cu2SnS3 nanoparticles for planar heterojunction solar cells

Abstract

Cu2SnS3 is a potential absorber material for thin film solar cells. However, Cu2SnS3 solar cells are normally prepared by high temperature sulfurization process. In this work, the Cu2SnS3 nanoparticle films with a porously structured surface are in situ prepared by a new and facile molecular precursor solution approach featuring a low annealing temperature (250 °C–350 °C) and a short annealing time (5 min); furthermore, the novel planar heterojunction solar cells configured as FTO/TiO2/CdS/Cu2SnS3/P3HT/MoO3/Ag are fabricated, in which poly(3-hexylthiophene) (P3HT), an organic conjugated polymer, mainly acts as hole transporting material. It is found that the annealing temperature imposes a significant influence on the structure of Cu2SnS3 nanoparticle film. While increasing annealing temperature leads to a higher crystallinity of Cu2SnS3 nanoparticle film, the pores on the film surface become larger at annealing temperature >300 °C. It is also revealed that the solar cell performance depends on the annealing temperature and Cu2SnS3 film thickness, and the efficiency of 2.03% is obtained in the solar cells with 60 nm thick Cu2SnS3 thin film prepared at 300 °C. The results here demonstrate a low-temperature solution preparation strategy to prepare Cu2SnS3 thin films for solar cells and other optoelectronic devices.