Innovative passivating contact using quantum well at poly-Si/c-Si interface for crystalline silicon solar cells

Herein, we propose a quantum well comprising a stack of SiOx/nanocrystalline silicon (nc-Si)/SiOx layers between a polycrystalline silicon (poly-Si) layer and a crystalline silicon wafer (c-Si) for enhancing the passivation quality through the poly-Si/c-Si passivating contact for c-Si solar cells. A large number of dopants can diffuse deeply into c-Si from a heavily doped poly-Si layer during high-temperature annealing, reducing the surface passivation quality. The quantum well with the double SiOx layer plays a significant role as a double barrier, thus suppressing this. The formation of the nc-Si phase sandwiched between the SiOx layers can support carrier transport, i.e., the tunnelling of carriers through the SiOx layers for collection. Moreover, a highly doped poly-Si/quantum well/c-Si contact exhibits considerable improvement in the passivation quality, achieving a high iVoc of 742 mV and low Jo of 1.1 fA/cm2, compared with a reference poly-Si/c-Si passivating contact (iVoc = 707 mV, Jo = 32.5 fA/cm2). The results indicate the effectiveness of the innovative passivating contact concept and pave the way for further improvements in the performance of c-Si solar cells.