Investigation of hetero-interface and junction properties in silicon heterojunction solar cells

The amorphous silicon (a-Si:H) - crystalline silicon (c-Si) heterojunction (SHJ) solar cell fill factor (FF) is very sensitive to the properties of c-Si surface, process parameters of thin a-Si:H layers, properties of transparent conducting front electrode, and all of their interfaces. In this work, quality of hetero-interface and junction properties in n-type SHJ solar cells were investigated by; (i) suns V_OC under white, blue, and infrared light; (ii) dark and light JV; and (iii) quantum efficiency (QE) with and without voltage and light bias. Analysis of all these measurements suggest an anomalous “S” shape JV curve can arise due to at least two separate reasons; (a) existence of a large barrier for hole transport with excellent front surface passivation, and (b) existence of an opposing diode/Schottky barrier in the hetero emitter side of a SHJ solar cell. Both of the above-mentioned interface and/or junction properties severely affect minority carrier collection in SHJ cells.