Performance enhancement of CIGS thin-film solar cells with a functional-window NiO thin layer

• Published in: Journal of alloys and compounds 2020-09, Vol.836, p.154803, Article 154803
• Main Authors: Youn, Sung-Min, Park, Min-Joon, Kim, Jin Hyeok, Jeong, Chaehwan
• Format: Article
• Language: English
• Subjects: Absorptivity; Carrier lifetime; Carrier recombination; CIGS; Copper indium gallium selenides; Electron affinity; Electron beam evaporators; Energy conversion efficiency; Energy gap; Functional layer; Nickel oxides; NiO; Performance enhancement; Photoluminescence; Photovoltaic cells; Room temperature; Solar cell; Solar cells; Thin film; Thin films; Transition metal oxide; Transition metal oxides
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2020.154803

Cu(In1-χGaχ)Se2 (CIGS) films have been considered as promising materials for solar cell applications owing to high absorption coefficient, bandgap grading, flexibility, and high conversion efficiency. In particular, the bandgap grading has been widely researched as a back surface field effect to reduce the carrier recombination. Recently, the front surface field has been researched by the application of a transition metal oxide (TMO) to increase the power conversion efficiency (PCE). Among them, NiO is an outstanding TMO layer because of its wide bandgap (∼3.7 eV), stable cubic structure, the low electron affinity of 1.33–1.85 eV and p-type characteristics. Consequently, the application of the NiO layer has been researched on the CIGS solar cells as an effective electron blocking barrier, which is to suppress the carrier recombination. Even though much research has proceeded on the versatile properties of the NiO, there is rarely research to apply the NiO layer on the CIGS solar cells yet. In this study, we introduced the application of NiO layer deposition on the CIGS solar cell to improve the PCE. The NiO layer (20 nm) was deposited on the CIGS solar cell using the E-beam evaporator system at room temperature. We investigated the effect of the application of the p-NiO layer on the CIGS solar cells, comparing the efficiencies and dark J-V curves. These results are in good agreement with time-resolved photoluminescence measurements on the carrier lifetime. The PCE of the device with the p-NiO layer was measured as 16.35% and the PCE of the device without the p-NiO layer was measured as 15.81%. After the application of the p-NiO layer, we gained the improvement with 0.54% of the PCE. •The p type NiO layer is proposed as an energy barrier for improvement of CIGS solar cells.•The NiO layers are evaporated by electron beam on CIGS solar cells.•Transmittance of NiO layers (20 nm) are an average of 95.37% and a bandgap as 3.7 eV.•Conversion efficiency with the p-NiO layer is increased with a gain of 0.54% at 16.35%.