Porous silicon solar cells with 13.66% efficiency achieved by employing graphene-quantum-dots interfacial layer, doped-graphene electrode, and bathocuproine back-surface passivation layer

Formation of Porous Si (PSi) enhances the light absorption of Si thanks to the increased surface-to-volume ratio, useful for improving the power conversion efficiency (PCE) of Si-based solar cells. Here, we first employ graphene quantum dots (GQDs) as an interfacial layer for better band alignment at the graphene (GR) transparent conductive electrode (TCE)/PSi interface. The PCE exhibits a maximum of 13.66%, highest ever achieved in GR/PSi solar cells, by doping the GR TCE and passivating the Si back surface in addition to the GQDs interfacial layer. The use of the interfacial and the passivating layers results in the reduction of the carrier recombination at the GR TCE/PSi and Si/cathode interfaces, respectively. The cell also shows excellent long-term stability by maintaining 84% of its original PCE even in air for 30 days.