Polysilicon Contact Structures for Silicon Solar Cells Using Atomic Layer Deposited Oxides and Nitrides as Ultra-thin Dielectric Interlayers
Polysilicon contact structures with ultra-thin atomic layer deposited (ALD) oxide and nitride interlayers based on SiOx, SiNx, AlOx, AlNx, and TiOx either as part of an interlayer stack when applied on top of a conventional thermally-grown SiOx or as a single interlayer were investigated. ALD SiOx single interlayers provided a very good passivation quality with high implied open-circuit voltage and low-specific contact resistivity when an optimal thickness and annealing temperature was applied. Also, ALD SiNx single interlayers showed a promising passivation quality, while AlOx and AlNx interlayers only allowed for a moderate and TiOx interlayers exhibited a very poor passivation quality. ALD SiOx interlayers on planar and textured silicon solar cells with poly-Si(p) hole-selective contacts and poly-Si(n) electron-selective contacts enabled a conversion efficiency of almost 21% as a proof-of-concept. These results are comparable with silicon solar cells with conventional thermally-grown SiOx, showing that ALD SiOx interlayers are an alternative to conventional thermally-grown SiOx in polysilicon contacts structures.