Investigation on limiting factors affecting Cu2ZnGeSe4 efficiency: Effect of annealing conditions and surface treatment
SOLAR ENERGY MATERIALS AND SOLAR CELLS(2020)
摘要
This work aims to unveil the optimal annealing conditions and surface treatments of CZGeSe absorbers, synthesized using vacuum-based deposition technique, with an eye to optimizing the main parameters allowing better control of secondary phases formation and improving crystalline quality of this absorber. Firstly, a comparative study is given of one and two-step annealing profiles, where, for each thermal treatment, the optimal temperature is probed. The second section of this study underlines the evaluation of the surface treatment effect on the as-annealed absorber using different etching agents. Finally, the effect of different post-annealing treatment temperatures on the overall performance of the fabricated devices is evaluated. For the studied optimizations, a deep understanding of the cell behavior is provided through structural, morphological and electrical characterizations. Preliminary results have given an efficiency up to 5.6% with higher V-oc = 572 mV and FF = 65% compared to the reported record cell using similar absorber (V-oc = 558 mV, FF = 59%). This performance is linked to the implementation of a two-step annealing process with lower temperatures (330 degrees C/480 degrees C) as it showed the best crystallinity-efficiency trade-off along with the smallest amount of ZnSe secondary phase among all the thermal routines studied. In addition, after the evaluation of several etching agents, the implementation of a KCN etching has shown to be the most effective leading to a remarkable improvement of the PN junction through a surface passivation.
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关键词
CZGeSe,Kesterite solar cells,Selenization,Chemical etching,Photovoltaic
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