Ionic selective contact controls the charge accumulation for efficient and intrinsic stable planar homo-junction perovskite solar cells

The under-coordinated ionic defects at the surface and grain boundaries of organic-inorganic halide perovskite always attract and trap the free carriers via the electrostatic force and accelerate the ions migration by defect vacancies channels, significantly limiting the charge extraction efficiency and intrinsic stability of perovskite solar cells (PSCs). Here, a novel strategy of ionic layer induced homo-junction perovskite reinforced the build in field (Ebi) is proposed to further decrease trap recombination and suppress the ions migration, thereby enhancing the power conversion efficiencies (PCEs) and intrinsic stability of PSCs. Experiments and theories certify that the adsorbed cations and anions will not only give rise to interface charge accumulation/depletion of perovskite, resulting in boarder distributed and reinforced Ebi, but also increased the interface ions vacancy migration barriers via the extra ionic interaction. As a result, the resultant n-i-p PSCs showed a record PCE of 20.88% among the organic electron transfer layer (ETL) and deliver a high stability of 88% after aged 60 days in atmosphere without encapsulation. Our findings provide a new insight to further eliminate the side effect of ionic defects and guide to design newly contact interface to minimize the trap recombination and ions motion induced intrinsic stability of PSCs.