Analysis of recombination mechanisms in heterojunction silicon solar cells with rapid thermally annealed thin film emitters

Abstract

A new family of silicon (Si) wafer heterojunction solar cells fabricated by solid phase crystallization of PECVD amorphous silicon emitters by rapid thermal annealing (RTA) has been analyzed in order to understand the dominant recombination mechanisms. Solar cells fabricated with a broad RTA temperature range of 600–1000 °C were characterized through quantum efficiency, illuminated I–V, and capacitance–voltage measurements. Using the experimental data and theoretical considerations, the influence of carrier recombination in the quasi-neutral and space charge zones as well as at the heterojunction interface were studied. It is established that the carrier recombination in the quasi-neutral base region in the p-type Si substrate predominantly limits the device open circuit voltage. The analysis also showed that the interface recombination velocities at the heterojunction were less than 100 cm s−1. It is also qualitatively established that a post-fabrication forming gas anneal reduces the defect density at the hetero-interface.