BT-MA0.6FA0.4PbI3-XClX Unsymmetrical Perovskite for Solar Cells with Superior Stability and PCE over 23%

Combining superior stability and high power conversion efficiency (PCE) is a challenge in 3D (three-dimensional) and 2D (two-dimensional) perovskite solar cell (PSC) research. Mitigating the limitations of the symmetrical 3D structure and 2D charge transmissive channel has also not been achieved. Analogous 2D unsymmetrical perovskite structure is an excellent strategy to establish a balance between stability and PCE. Here, the BT (1,2,4,5-benzenetetramine tetrahydrochloride)-MA(0.6)FA(0.4)PbI(3-x)Cl(x) analogous 2D unsymmetrical perovskite film is applied to improve the PCE and stability of PSCs. The BT groups substitute the formamidinium and methylammonium ions, interact with lead trihalide to form a bond, and prevent the formation of vacancy traps from amino groups. The high electron density and extensive delocalized electrons of pi-conjugated heterocycles of BT enhance charge transport and separation. The chloride from BT provides a rich halogen environment, which further improves the quality of the perovskite film. The BT-MA(0.6)FA(0.4)PbI(3-x)Cl(x) PSC exhibits superior PCE and stability, simultaneously. The champion PCE is up to 23.33%, which is also a record PCE for MAPbI(3-x)Cl(x) PSCs. Compared with the pristine MA(0.6)FA(0.4)PbI(3-x)Cl(x) PSC, the stability of the optimized device is improved by 10-20% under different conditions. The enhanced performance is ascribed to the stable unsymmetrical structure, excellent charge transport, and high quality of the perovskite film.

Automated summary

By using a BT-MA(0.6)FA(0.4)PbI(3-x)Cl(x) film with an unsymmetrical 2D perovskite structure, the power conversion efficiency and stability of perovskite solar cells can be improved. The incorporation of BT groups enhances charge transport and prevents the formation of vacancy traps, resulting in superior performance with a champion PCE of 23.33% and improved stability of 10-20%.