Thin film solar cell based on p-CuSbS2 together with Cd-free GaN/InGaN bilayer

Abstract

CuSbS2 thin film solar cell with 2.99 % efficiency has been demonstrated by using the Cd-free GaN and In0.15Ga0.85N as n-type semiconductor bilayer. CuSbS2 films on the TiN-coated Mo/glass substrates were made by co-sputtering technique at 300 °C with a cermet target of (Cu + Sb2S3) operated at 50–60 W and a metal target of Cu at 2 W, followed by thermal annealing at 350–450 °C for 1 h. The effects of processing conditions on the growth behavior, microstructural characteristics, and electrical properties of CuSbS2 films had been investigated. Solar cell devices were fabricated by depositing ~50 nm GaN and ~300 nm In0.15Ga0.85N layers with low temperature radio-frequency (RF) sputtering method, followed by RF sputtering 300–400 nm indium-tin oxide for front contact and pasting silver glue for electric contacts. The CuSbS2 thin film sputtered at 55 W had a [Cu]/[Sb] ratio of 0.80 with co-exists of the Sb2S3, and had a hole concentration of 1.41 × 1018 cm−3, an electrical conductivity 0.1 S cm−1, and mobility of 13 cm2 V−1 s−1. The efficiency of the solar cell device had a 3.83-fold increase if the p-CuSbS2/CdS/n-ZnO system had its conventionally designed CdS/n-type ZnO layer replaced by n-type GaN/In0.15Ga0.85N bilayer.