Stability Improvement of Perovskite Homojunction by Inhibiting the Diffusion of Doping Defects

Perovskite homojunction can promote the separation and oriented transportation of the photocarriers through the built‐in electric field, and weaken the dependence of solar cells on the charge transport layer. Although the perovskite homojunction shows great advantages in improving device efficiency, it retains the inherent poor stability of perovskite materials. Herein, it is found that donor defects (MA + interstitial, I − vacancy, etc.) in the n‐type layer are prone to compensate the acceptor defects (MA + vacancy, I − interstitial, etc.) in the p‐type layer. This compensation behavior results from the diffusion of doping defects driven by a concentration gradient, which leads to the weakening of the built‐in electric field. Furthermore, phenethylammonium iodide is introduced into the perovskite homojunction to inhibit the defect diffusion, which enhances the stability of the homojunction and the corresponding solar cells. After modification, the efficiency of perovskite homojunction solar cells is improved from 8.60% to 9.60%, and retains 80% (standard ≈30%) of initial efficiency after 1000 h aging.