Researchers from Professor Tan Hairen group at Nanjing University in China recently developed all-perovskite tandem solar cells with a conversion efficiency of 26.4%, certified by JET.

The team developed ammonium-cation-passivated Pb-Sn perovskites with long diffusion lengths, enabling subcells with an absorber thickness of ~1.2 μm. Molecular dynamics simulations suggest that widely-used phenethylammonium (PEA) cations are only partially adsorbed on the surface defective sites at perovskite crystallization temperatures. The passivator adsorption is predicted to be enhanced using 4-trifluoromethyl-phenylammonium (CF3-PA), which exhibits a stronger perovskite surface-passivator interaction than does PEA.

By adding a small amount of CF3-PA into precursor solution, the team increased the carrier diffusion length within Pb-Sn perovskites by 2x, to over 5 μm, and increased the efficiency of Pb-Sn perovskite solar cells to over 22%.

The team also made previous progress in large-area all-perovskite tandem solar cells modules. A tandem solar cell module with a certified efficiency of 21.7% was developed by adopting industrialized preparation technology.