Efficient crystalline Si solar cell with amorphous/crystalline silicon heterojunction as back contact

We study an amorphous/crystalline silicon heterojunction (Si HJ) as a back contact in industrial standard p-type five-inch pseudo-square wafer to replace Al back surface field (BSF) contact. The best efficiency in this study is over 17% with open-circuit (V_oc) of 0.623 V, which is very similar to the control cell with Al BSF. We found that V_oc has not been improved with the heterojunction structure in the back. The typical minority carrier lifetime of these wafers is on the order of 10 μs. We also found that the doping levels of p-layer affect the FF due to conductivity and band gap shifting, and an optimized layer is identified. We conclude that an amorphous/crystalline silicon heterojunction can be a very promising structure to replace Al BSF back contact.