Charge carrier management for highly efficient perovskite/Si tandem solar cells with poly-Si based passivating contacts

Abstract

Integrating wide-bandgap organic–inorganic lead halide perovskite absorber layers with Si bottom solar cells into tandem architectures offers significant potential for increasing power conversion efficiency (PCE). However, achieving high-performance monolithic tandem devices remains challenging, particularly when processing perovskite top cells on top of industrial silicon bottom cells, featuring polycrystalline silicon on oxide (POLO) passivating contacts, as implemented in “TOPCon” solar cells. Here, we employ an advanced silicon bottom cell architecture incorporating full-area electron-selective POLO front contacts and laser-structured hole-selective POLO back contacts. We perform the N₂ annealing at an elevated temperature of silicon bottom cells, effectively curing sputter-induced damage in the full-area electron-selective POLO contact of the recombination junction and enhancing the interface between transparent conductive oxide and the n-type doped poly-Si layer. Additionally, this annealing treatment likely improves the rear small-area contact between the aluminum (Al) and the p⁺ poly-Si. Furthermore, we investigate how the nickel oxide layer regulates the substrate morphology and affects the charge carrier mechanisms for the top perovskite solar cells. These strategies remarkably promote charge carrier management, achieving a monolithic perovskite/POLO-Si tandem solar cell with a PCE of 31%. Moreover, the unencapsulated tandem cell retained 93% of its initial efficiency after operating for 240 hours at maximum power point under one sun intensity, 25 °C, and 30% relative humidity (ISOS-L-1), the extrapolated T₈₀ lifetime is estimated to be 740 hours.