A multifunction europium oleate passivation layer coated on surface of a MAPbI₃ film improves the moisture resistance, thermal dissipation, and hole extraction efficiency of perovskite solar cells (PSCs) through interacting with defect sites. This strategy simultaneously enhances the stability and power conversion efficiency (PCE) of PSCs, dramatically extending the T ₈₀ lifetime and achieving a champion PCE of 18.99 %.

Europium oleate (Eu(OA)₃) is designed as a multifunctional passivation layer coated onto methylammonium lead iodide (MAPbI₃) films to delay the degradation of perovskite solar cells (PSCs) caused by moisture and heat. The carbonyl group and Eu³⁺ ions of Eu(OA)₃ subsequently coordinate with uncoordinated Pb²⁺ and I⁻ ions to form a moisture-proof and heat-dissipating layer anchored onto both top and side surfaces of the perovskite film. The hydrophobicity of the MAPbI₃ film treated by Eu(OA)₃ remarkably increases, as demonstrated by the enhancement of the average contact angle from 54.9° to 90.5°. Besides, the thermal conductivity of PSCs incorporated with Eu(OA)₃ is 1.3 times that of the control device, resulting in a 1.34 °C reduction on surface temperature at 85 °C. The optimized PSCs demonstrate a T ₈₀ lifetime of 1056 h (only 180 h for pristine PSCs) at conditions of room temperature and relative humidity (RH) of 40%. Moreover, the T ₈₀ lifetime for optimized PSCs is four times that of the control device at 85 °C and RH of 85%. Finally, the power conversion efficiency (PCE) of PSCs treated with Eu(OA)₃ increases from 17.36 to 18.99%, attributed to the effective defect passivation and suppression of nonradiative recombination.