Effect of doping concentration of tunnel junction on I-V characteristics of photovoltaic power converter

Abstract Tunnel junction is the crucial part for photovoltaic power converters, especially for those with the multi-junction structure. In this research, through changing growing temperature and the ratio of V-III precursor, four single-junction photovoltaic power converters with tunnel junction of different doping concentrations are fabricated. The I - V characteristics of four samples are measured, and also their power conversion efficiency and fill factors are calculated. It was found that the I - V curves of the samples exhibited significant differences as the doping concentration increased. Within an appropriate range, the photovoltaic power converter with higher doping concentration exhibits higher power conversion efficiency. However, when the doping concentration is too high, a reverse barrier appears inside the tunnel junction, manifesting as a “stair” I - V curve. This barrier will result in a reduction in device efficiency. This work provides important guidance for designing the doping concentration of tunnel junctions and fabricating high-performance photovoltaic power converters.