Charged defects at the surface of the organic–inorganic perovskite active layer are detrimental to solar cells due to exacerbated charge carrier recombination. Here we show that charged surface defects can be benign after passivation and further exploited for reconfiguration of interfacial energy band structure. Based on the electrostatic interaction between oppositely charged ions, Lewis-acid-featured fullerene skeleton after iodide ionization (PCBB-3N-3I) not only efficiently passivates positively charged surface defects but also assembles on top of the perovskite active layer with preferred orientation. Consequently, PCBB-3N-3I with a strong molecular electric dipole forms a dipole interlayer to reconfigure interfacial energy band structure, leading to enhanced built-in potential and charge collection. As a result, inverted structure planar heterojunction perovskite solar cells exhibit the promising power conversion efficiency of 21.1% and robust ambient stability. This work opens up a new window to boost perovskite solar cells via rational exploitation of charged defects beyond passivation.

3D organic–inorganic hybrid halide perovskite solar cells (pero‐SCs) inherently face severe instability issue due to ion migration under operational conditions. This ion migration inevitably results from the decomposition of ionic bonds under lattice strain and is accelerated by the existence of excess charge carriers. In this study, a 1D–3D mixed‐dimensional perovskite material is explored by adding an organic salt with a bulk benzimidazole cation (Bn+). The Bn+ can induce 3D perovskite crystalline growth with the preferred orientation and form a 1D BnPbI3 perovskite spatially distributed in the 3D perovskite film. For the first time, the electro‐strictive response, which has a significant influence on the lattice strain under an electric field, is observed in polycrystalline perovskite. The 1D–3D perovskite can effectively suppress electro‐strictive responses and unbalanced charge carrier extraction, providing an intrinsically stable lattice with enhanced ionic bonds and fewer excess charge carriers. As a result, the ion migration behavior of the p‐i‐n 1D–3D based pero‐SC is dramatically suppressed under operational conditions, showing ultra‐long‐term stability that retains 95.3% of its initial power conversion efficiency (PCE) under operation for 3072 h, and simultaneously achieving an excellent PCE with a hysteresis‐free photovoltaic behavior.

The power conversion efficiency (PCE) of planar p–i–n perovskite solar cells (pero‐SCs) is commonly lower than that of the n–i–p pero‐SCs, due to the severe nonradiative recombination stemming from the more p‐type perovskite with prevailing electron traps. Here, two n‐type organic molecules, DMBI‐2‐Th and DMBI‐2‐Th‐I, with hydrogen‐transfer properties for the doping of bulk perovskite aimed at regulating its electronic states are synthesized. The generated radicals in these n‐type dopants with high‐lying singly occupied molecular orbitals enable easy transfer of the thermally activated electrons to the MAPbI3 perovskite for the realization of n‐doped perovskites. The n‐doping degree could be further enhanced by using the iodine ionized dopant DMBI‐2‐Th‐I. The doping effect could reduce the electron trap density, increase the electron concentration of the bulk perovskite, and simultaneously improve the surface electronic contact. When the DMBI‐2‐Th‐I‐doped perovskite is used in planar p–i–n pero‐SCs, the nonradiative recombination is significantly suppressed. As a result, the photovoltaic performance improved significantly, as evidenced by an excellent PCE of 20.90% and a robust ambient stability even under high relative humidity. To the best of the knowledge, this work represents the first example where organic n‐type dopants are used to tune the electronic states of a bulk perovskite film for efficient planar p–i–n pero‐SCs.

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