Bandgap tunable CdS:O as efficient electron buffer layer for high-performance Sb2Se3 thin film solar cells

• Published in: Solar energy materials and solar cells 2019-06, Vol.194, p.47-53
• Main Authors: Ou, Chizhu, Shen, Kai, Li, Zhiqiang, Zhu, Hongbing, Huang, Tailang, Mai, Yaohua
• Format: Article
• Language: English
• Subjects: Antimony; Antimony compounds; Atomic oxygen; Band alignment; Buffer layers; Cadmium; Cadmium sulfide; CdS:O; Efficiency; Electromagnetic absorption; Electron buffer layer; Electrons; Energy gap; Heterojunctions; Optimization; Oxygen; Oxygen content; Photovoltaic cells; Photovoltaics; Sb2Se3; Selenide; Selenides; Solar cell; Solar cells; Thin films; Toxicity
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2019.01.043

Antimony selenide (Sb2Se3) is a promising low-cost and low-toxicity photovoltaic material. The electron buffer layer is of great significance for superstrate Sb2Se3 thin film solar cells. Herein, high-performance Sb2Se3 solar cells were fabricated by using sputtered, bandgap-tunable oxygenated cadmium sulfide (CdS:O) as a novel class of electron buffer layers. The optical transparency and energy band levels of CdS:O buffers were precisely adjusted by controlling the oxygen content in CdS:O layers. With the incorporation of an optimized wide band-gap CdS:O electron buffer layer, the device parameters JSC, VOC and FF were all improved. An efficiency of as high as 6.29% was achieved. It's found that, besides the reduced light absorption in the CdS:O layer, the high-quality CdS:O/Sb2Se3 junction played a vital role in the efficiency enhancement. The optimization of interfacial band alignment and defects passivation by atomic oxygen both contribute to the improved quality of CdS:O/Sb2Se3 heterojunction. This study demonstrates that the sputtered CdS:O is a promising electron buffer layer for preparation of high-efficiency and large-area Sb2Se3 thin film solar cells. •The CdS:O/Sb2Se3 solar cells were fabricated using sputtered, bandgap-tunable CdS:O as a novel class of electron buffer.•Both extended spectral response and improved heterojunction quality lead to an efficiency improvement from 4.10% to 6.29%.•The conductive band offset at the CdS:O/Sb2Se3 interface was optimized by adjusting the energy band of CdS:O buffer layers.