Tailoring the work function of Mo for efficient CZTSe solar cells
Jianyu Wu a, Shengli Zhang a, Hongling Guo a, Yue Liu a, Yi Zhang a
a Nankai University, 94 Weijin Road, Nankai District, Tianjin 300071, China
Proceedings of International Conference on Advanced Light Absorbing Materials for Next Generation Photovoltaics (ABSOGEN)
Online, Spain, 2020 November 17th - 18th
Organizers: Hongxia Wang, Xiaojing Hao and Lydia Wong
Poster, Jianyu Wu, 021
Publication date: 6th November 2020

Open-circuit voltage deficit (VOC-deficit) is a crucial issue in the development of kesterite Cu2ZnSnSe4 (CZTSe) solar cells, as several factors can restrict VOC. The undesirable energy band structure is a serious limitation to boost VOC. Therefore, a mechanism is investigated in this work to optimize the energy band alignment at the back interface by adjusting the work function of the molybdenum electrode. Na3PO4 solution is used to process the Mo electrode. As phosphorus diffuses into molybdenum and bonds with Mo as anions, the work function of the Mo electrode can be increased from 4.6 eV to 5.6 eV. The formation of voids in a fine-grain CZTSe layer can be suppressed effectively by Na. A substantial increase in VOC is, therefore, obtained by a combined action of P and Na. The simulation and comparative experiment indicate the effect of P and Na on boosting VOC. After the optimization of the process, the efficiency of CZTSe solar cells increase from 6.8% to 9%. It is logically inferred that this work function tailoring method may be applied to other solar cells and electronic devices utilizing Mo as an electrode.

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