Nanoarray heterojunction and its efficient solar cells without negative impact of photogenerated electric field

Abstract

Efficient, stable and low-cost solar cells are being desired for the photovoltaic conversion of solar energy into electricity for sustainable energy production. Nanorod/nanowire arrays of narrow-bandgap semiconductors are the promising light-harvesters for photovoltaics because of their excellent optoelectrical properties. Here, the array of preferentially oriented antimony trisulfide (Sb2S3) single-crystalline nanorods is grown on polycrystalline titania (TiO2) film by a tiny-seed-assisted solution-processing strategy, offering an Sb2S3/TiO2 nanoarray heterojunction system on a large scale. It is demonstrated that the Sb2S3 nanorod growth follows a tiny-seed-governed orientation-competing-epitaxial nucleation/growth mechanism. Using a conjugated polymer hole transporting layer on the heterojunction, we achieve a power conversion efficiency of 5.70% in the stable hybrid solar cell with a preferred p-type/intrinsic/n-type architecture featuring effectively straightforward charge transport channels and no negative impact of photogenerated electric field on device performance. An architecture-dependent charge distribution model is proposed to understand the unique photovoltaic behavior.