Spontaneous relaxation of 2D passivation layer contributes to the aging-induced performance enhancement of perovskite solar cells

The aging-induced performance enhancement of the perovskite solar cells (PSCs) has been considered to be associated with the oxidation progress of the hole-transporting layer. Whereas the influence of the structural evolution of the passivation layer is underestimated. In this work, a spontaneous relaxation of two-dimensional (2D) passivation layer with increased n-value structure is observed, which can be accelerated under ambient atmosphere. It is demonstrated that device with relaxed 2D passivation layer exhibits reduced non-radiative recombination and optimized charge transfer property, contributing substantially to the aging-induced performance enhancement in 2D-3D heterostructured PSCs. Finally, a high fill factor of 84.15% of the devices is obtained with the relaxed 2D passivation layer, suggesting the spontaneous relaxation of 2D passivation layer is playing a key role in achieving high quality optoelectronic devices.