Highly efficient and stable wide-bandgap perovskite solar cells via strain management

Abstract

Abstract Wide-bandgap (WBG) perovskite solar cells (PSCs) with high performance and stability are in considerable demand in the photovoltaic market to boost tandem solar cell efficiencies. Perovskite bandgap broadening results in a high barrier for enhancing the efficiency of the PSCs and causes phase segregation in perovskite. In this study, we show that the residual strain is the key factor affecting the WBG perovskite device efficiency and stability. The DMSO addition not only helps lead halide to with opening the vertical layer spacing to form (CsI)0.08(PbI1.4Br0.6) and (CsI0.125Br0.875)0.08(PbI1.2Br0.8) intermediate phases, but also provide more nucleation sites to eliminate lattice mismatch with FAX (X = I, Br or Cl) or MAX, which dominates the strain effects on the WBG perovskite growth in a sequential deposition. By minimizing the strain, 1.67- and 1.77-eV nip devices with record efficiencies of 22.28% and 20.45%, respectively, can be achieved. The greatly enhanced suppression of phase segregation enables the device with retained 90% - 95% of initial efficiency over 4000 h of damp stability and 80% - 90% of initial efficiency over 700 h of maximum-power-point output stability under full-spectrum light without encapsulation. Besides, the 1.67-eV pin devices can achieve a competitive 22.3% efficiency while achieving considerable damp-heat, pre-ultraviolet (pre-UV) aging, and MPP tracking stability as per the tests conducted according to IEC 61215. The final efficiency for the perovskite/Si tandem is more than 28.3 %, which matches the top efficiencies reported to date.