Boosting Conversion Efficiency in Zn3P2/InP Solar Cells Via Nanoscale Junction Engineering

Zinc phosphide () shows great promise for next-generation photovoltaics made of earth-abundant elements. To date, the poor crystal quality is limiting conversion efficiency to 4.4% for heterojunction and to 6% for Schottky junction solar cell. This work presents the fabrication and characterization of /InP solar cells with a new record efficiency of 8%. The material quality is significantly improved by using selective area epitaxy (SAE) in conjunction with a post-growth annealing. The combination of current-voltage (J-V) measurements and electron beam induced current (EBIC) mapping, alongside with optical and electrical simulations, outline the impact of the SAE pattern dimensions on the device performances. A decrease in the opening area fraction is associated with an increase in the VOC and a decrease in the JSC. Our results suggest that the degradation of the VOC for large openings is predominantly attributable to the presence of misfit dislocations at the heterojunction interface. On the other hand, the reduced JSC for small openings is associated with a smaller electron diffusion length, which is attributed to the current crowding effect. Finally, the device’s stability under outdoor testing over a year is demonstrated.