Detailed Study on the Role of Nature and Distribution of Pinholes and Oxide Layer on the Performance of Tunnel Oxide Passivated Contact (TOPCon) Solar Cell

Industrial silicon solar cells are now mostly based on aluminum back surface field (Al-BSF) or passivated emitter rear cell (PERC) technologies on p-type crystalline silicon wafers. Recently tunnel oxide passivated contact (TOPCon) solar cell on p-type Si wafers has attracted attention due to its demonstrated higher efficiency than either Al-BSF or PERC type solar cell. Numerical analysis using 3-D Sentaurus Technology Computer Aided Design (3-D-TCAD) software leads to the enhancement of the efficiency of the p- and n-type TOPCon solar cells by optimizing the size, nature, and number density of pinholes in the oxide layer; thickness of the oxide layer with and without pinholes and B doping concentration in the hole selective p+ poly-Si layer at the rear. Effects of both types of pinholes, either completely through (physical contact) or partially through (localized thinner oxide), are studied on cell performance. Simulation results show that pinholes in tunnel oxide have an advantage in lowering of series resistance and improvement of fill factor. To achieve optimum performance, the size, nature, and number density of pinholes and thickness of the oxide layer should be optimized. Considering both types of pinholes, the efficiency achieved is 25.3% for p-TOPCon and 26% for n-TOPCon. Also, the outputs of simulated p-TOPCon are compared with simulated p-PERC solar cell. The analysis shows that TOPCon solar cell on p-type wafer has significant ability to be adopted for industrial production.