Analysis of the diffused front surface field of n-type silicon solar cells with a-Si/c-Si heterojunction rear emitter

In this work, we focus on the optimization of small-area n +np+ n-type silicon solar cells featuring an amorphous/crystalline silicon heterojunction (a-Si:H/c-Si SHJ) rear emitter. For cells with a locally c-Si(n++) diffused high-low junction underneath the front side metallization and a full-area c-Si(n+) diffused front surface field (FSF) in between, efficiencies of up to 20.6 % have been reached. It is shown by experiment and two-dimensional device simulation that when omitting the full-area c-Si(n+) FSF a sufficient two-dimensional majority carrier transport via the base to the local c-Si(n++) FSF can be secured. For the front side passivation of the c-Si base a stack of thermal SiO2 / SiNx and Al2O3 / SiNx was applied