Researchers from South China University of Technology, The Chinese University of Hong Kong, Chinese Academy of Sciences (CAS), National Center for Nanoscience and Technology, Friedrich-Alexander University Erlangen-Nürnberg and Linköping University set out to eliminate deep traps in inorganic narrow bandgap (NBG) perovskites, in order to enable the successful development of 2T inorganic perovskite tandem solar cells (IPTSCs).
The team explained that all-inorganic perovskites prepared by substituting the organic cations (e.g. methylammonium (MA+) and formamidinium (FA+)) with inorganic cations (e.g. Cs+) are effective concepts to enhance the long-term photo- and thermal-stability of perovskite solar cells (PSCs). Hence, inorganic perovskite tandem solar cells (IPTSCs) are promising candidates for breaking the efficiency bottleneck and addressing the stability issue as well. However, challenges in fabricating 2-terminal (2T) IPTSCs due to the inferior film formation and deep trap states induced by tin cations hinder that option.
In their recent work, a ligand evolution (LE) strategy with p-toluenesulfonyl hydrazide (PTSH) was employed to regulate film formation and eliminate deep traps in inorganic narrow bandgap (NBG) perovskites, enabling the successful development of 2T IPTSCs.
Accordingly, the 1.31 eV CsPb0.4Sn0.6I3:LE device delivered a record efficiency of 17.41%. Combined with the 1.92 eV CsPbI2Br top-cell, 2T IPTSCs exhibited a champion efficiency of 22.57% (certified 21.92%).
Additionally, IPTSCs were engineered to deliver remarkable durability under maximum power point (MPP) tracking, maintaining 80% of the initial efficiency at 65 °C for 1510 h and at 85°C for 800 h, respectively.
The scientists stated that LE deliberately leverages multiple roles for inorganic NBG perovskite growth and anticipate their study will provide insightful guideline for developing high-efficiency and stable IPTSCs.
