5 years ago

Room-Temperature Processed Nb2O5 as the Electron-Transporting Layer for Efficient Planar Perovskite Solar Cells

Room-Temperature Processed Nb2O5 as the Electron-Transporting Layer for Efficient Planar Perovskite Solar Cells
Zhike Liu, Fupeng Wu, Wanli Ma, Xun Tang, Yongjie Wang, Dongyang Liu, Guozheng Shi, Si Chen, Jianyu Yuan, Jiawei Zheng, Haihua Wu, Shengzhong (Frank) Liu, Xufeng Ling, Feng Jin, Yannan Zhang
In this work, we demonstrate high-efficiency planar perovskite solar cells (PSCs), using room-temperature sputtered niobium oxide (Nb2O5) as the electron-transporting layer (ETL). Widely spread ETL-like TiO2 often requires high-temperature (>450 °C) sintering, which is not desired for the fabrication of flexible devices. The amorphous Nb2O5 (labeled as a-Nb2O5) ETL, without any heat treatment, can give a best power conversion efficiency (PCE) of 17.1% for planar PSCs. Interestingly, the crystalline Nb2O5 (labeled as c-Nb2O5), with high-temperature (500 °C) annealing, results in a very similar PCE of 17.2%, indicating the great advantage of a-Nb2O5 in energy saving. We thus carried out a systematical investigation on the properties of the a-Nb2O5 film. The Hall effect measurements indicate both high mobility and conductivity of the a-Nb2O5 film. Kelvin probe force microscopy measurements define the Fermi levels of a-Nb2O5 and c-Nb2O5 as −4.31 and −4.02 eV, respectively, which allow efficient electron extraction at the Nb2O5/perovskite interface, regardless of the additional heat treatment on Nb2O5 film. Benefitting from the low-temperature process, we further demonstrated flexible PSCs based on a-Nb2O5, with a considerable PCE of 12.1%. The room-temperature processing and relatively high device performance of a-Nb2O5 suggest a great potential for its application in optoelectrical devices.

Publisher URL: http://dx.doi.org/10.1021/acsami.7b05113

DOI: 10.1021/acsami.7b05113

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