Decoupling photothermal-mechanical degradation through lattice-stabilizing networks in Sn–Pb perovskites and all-perovskite tandem solar cells

All-perovskite tandem solar cells (PTSCs) demonstrate exceptional potential to surpass the Shockley-Queisser (SQ) theoretical limit. However, practical implementation faces critical challenges due to a self-reinforcing photothermal-mechanical degradation mechanism originating from multiscale physical couplings. In this study, a multifunctional polyamine ligand triphenyltriamine thiophosphate (TPTA) was introduced into the tin-lead (Sn-Pb) perovskite solution system to establish an I-Sn-N coordination-mediated lattice stabilization framework, and the photothermal-mechanical coupling path was cut off from multiple aspects such as suppressing periodic oscillations and regulating stress. Consequently, single-junction Sn-Pb perovskite solar cells (PSCs) achieve a power conversion efficiency (PCE) of 23.4% and retaining 94.9% of initial performance after 950 hours of maximum power point (MPP) tracking. When the device is integrated into the 2-terminal (2 T) tandem architecture, its PCE reaches a significant level of 29.6 % (certified PCE of 28.9%), and 93.4% of the initial efficiency can be maintained after 900 hours continuous operation. Practical implementation of all-perovskite tandem solar cells faces challenges due to the self-reinforcing photothermal-mechanical degradation mechanism. Here, authors employ a polyamine ligand to establish I-Sn-N coordination for stabilizing lattice framework, achieving device efficiency of 29.6%.