Study on the improvement of the open-circuit voltage of NiOx/Si heterojunction solar cell

Heterojunction solar cell based on nickel oxide (NiOx) as hole selective layer and n-type silicon as an active absorption layer is a promising high-efficiency solar cell. Unfortunately, this type of solar cells suffers from a low open circuit voltage (VOC) which limits any significant progress in its performance. Therefore, the main scope of this study is focused on VOC improvement. Discrete traps at the NiOx/Si interface are taken into account in the simulation to describe the real situation. The simulation was performed by SILVACO-Atlas using the interfacial traps NiOx/Si concentrations and hole mobility as tools to obtain agreement with measurement reported by Hsu et al. in [Thin Solid Films. 573 (2014) 159–163]. These parameters were found to be the cause of the low VOC value. VOC and efficiency improvements were achieved by optimizing the NiOx thickness and insertion a hydrogenated amorphous Si (a-Si:H) thin layer with optimal properties (electron affinity, bandgap and thickness)as a buffer layer between NiOx and Si. VOC increased from 423 to 906.16 mV and a good promising efficiency of η=12.73% is obtained in comparison to the initial efficiency (4.50%).