ABSTRACT
Wide-bandgap metal halide perovskites have demonstrated promise in multijunction photovoltaic (PV) cells. However, photoinduced phase segregation and the resultant low open-circuit voltage (Voc) have greatly limited the PV performance of perovskite-based multijunction devices. Here, a alloying strategy is reported to achieve uniform distribution of triple cations and halides in wide-bandgap perovskites by doping Rb+ and Cl- with small ionic radii, which effectively suppresses halide phase segregation while promoting the homogenization of surface potential. Based on this strategy, a Voc of 1.33 V is obtained from single-junction perovskite solar cells, and a VOC approaching 3.0 V and a power conversion efficiency of 25.0% (obtained from reverse scan direction, certified efficiency: 24.19%) on an 1.04 cm2 photoactive area can be achieved in a perovskite/perovskite/c-Si triple-junction tandem cell, where the certification efficiency is by far the greatest performance of perovskite-based triple-junction tandem solar cells. This work overcomes the performance deadlock of perovskite-based triple-junction tandem cells by setting a materials-by-design paradigm.
ABSTRACT
Monolithic perovskite/silicon tandem solar cells have been attracted much attention in recent years. Despite their high performances, the stability issue of perovskite-based devices is recognized as one of the key challenges to realize industrial application. When comes to the perovskite top subcell, the interface between perovskite and electron transporting layers (usually C60) significantly affects the device efficiency as well as the stability due to their poor adhesion. Here, different from the conventional interfacial passivation using metal fluorides, a hybrid intermediate layer is proposed-PMMA functionalized with ionic liquid (IL)-is introduced at the perovskite/C60 interface. The application of PMMA essentially improves the interfacial stability due to its strong hydrophobicity, while adding IL relieves the charge accumulation between PMMA and the perovskite. Thus, an optimal wide-bandgap perovskite solar cells achieves power conversion efficiency of 20.62%. These cells are further integrated as top subcells with silicon bottom cells in a monolithic tandem structure, presenting an optimized PCE up to 27.51%. More importantly, such monolithic perovskite/silicon cells exhibit superior stability by maintaining 90% of initial efficiency after 1200 h under continuous illumination.