Grain Regrowth and Bifacial Passivation for High-Efficiency Wide-Bandgap Perovskite Solar Cells

摘要

The wide-bandgap perovskite solar cell is a crucial part of perovskite/silicontandem solar cells, which offer an avenue for surpassing the power conversionefficiency (PCE) limit of single-junction silicon solar cells. However, theactual efficiency of such tandem solar cells today is diminished by the nonradiativerecombination losses in the wide-bandgap perovskite subcells. Here,this work reports a grain regrowth and bifacial passivation (GRBP) strategy toreduce recombination losses at the grain boundaries and perovskite/chargetransport layer interfaces simultaneously. This is achieved by a posttreatmentof perovskite films with a mixture of methylammonium thiocyanate (MASCN)and phenethylammonium iodide (PEAI). The MASCN induces the regrowth ofperovskite grains and simultaneously facilitates the penetration of PEAI intothe hole-transport-layer (HTL)/perovskite bottom interface. Thereby, the bulkand interface nonradiative recombination losses are reduced and the opencircuitvoltage in solar cells is considerably increased. PCEs of 21.9% and19.9% for the 1.65-eV bandgap opaque and semitransparent perovskite solarcells, respectively, are obtained. The encapsulated semitransparent perovskitesolar cells retain their initial efficiency following 500 h of operation underone-sun illumination in ambient conditions. The perovskite/silicon 4-terminal(4-T) tandem cells are fabricated with impressive PCEs 29.8% and 28.5% for0.049 cm~2 and 1 cm~2 devices, respectively.