Heterojunction with organic thin layer for three dimensional high performance hybrid solar cells

Abstract

Hybrid solar cells based on composites of silicon nanopillar arrays (SiNPs) on silicon substrates and conjugated polymer were investigated in this study. SiNPs with three dimensional (3D) geometry could orthogonalize the directions of light absorption and charge transfer while allowing for enhanced light scattering and trapping. In addition, SiNPs were fabricated by a simple process at low temperature and displayed strong light trapping capability over a wide range of incidence angles as well as near infrared light absorption. Furthermore, a method to control the density of SiNPs had been developed to obtain pillar arrays with controllable distance, which allowed conjugated polymer to reach the bottom part of SiNPs. The thickness of organic layer played a critical role on the short-circuit current, open-circuit voltage and fill factor, and optimum thickness was indispensable to achieve the superior performance. A power conversion efficiency of 9.2% was achieved based on the heterojunction with organic thin layer under AM 1.5G illumination at 100 mW cm−2. We believe that this model is appropriate for the fabrication of heterojunction hybrid devices based on alternative organic semiconductors or even inorganic semiconducting nanocrystals.