Alternative back contacts for Sb2Se3 solar cells

In this study, alternative back contacts for Sb2Se3 solar cells are explored with an aim to replace commonly used expensive gold electrode. Various low-cost contacts were tested including large work function metals such as Ni and Co. The performance of solar cells with bare metallic electrodes was lower up to 45% when compared to the reference device with Au contact, and was attributed mainly to the large back interface barrier for hole extraction. Additionally, shunt resistance of solar cells decreased significantly when Ni contact were employed as a result of metal diffusion and formation of interface defects. Thermally evaporated thin NiOx was used as a blocking layer for diffusion and mitigating hole extraction barrier. Solar cells with 7 nm of NiOx layer and Ni contact achieved 97% of reference solar cell performance. Over the period of 25 days, solar cells with 7 nm NiOx/Ni as a back contact retained 93% of initial performance, demonstrating that Au contacts can be successfully replaced by low-cost materials and retain high performance.