Solar cells based on organic−inorganic hybrid lead-halide perovskites are very promising because of their high performance and solution process feasibility. Elemental engineering on perovskite composition is a facile path to obtain high-quality crystals for efficient and stable solar cells. It was found that partially substituting I − with Cl − in the perovskite precursor promoted crystal growth, with the grain size larger than the layer thickness, and facilitated the generation of a selfpassivation layer of PbI 2 . Whereas the residual Cl − ions were suspected to diffuse to the hole-transport layer consisting of ubiquitously spiro-OMeTAD, the formation of highly bounded ionic pairing of Cl − with the oxidized state of spiro-OMeTAD led to insufficient charge extraction and severely reversible performance degradation. This issue was effectively alleviated upon Br − doping owing to the generation of Pb−Br bonds in the lattice that strengthened the phase stability by improving the binding energy between each unit. The binary halide (Br − / Cl − )-doped perovskites resulted in a champion power conversion efficiency of 20.2% with improved long-term storage stability.

Nonradiative recombination losses originating from crystallographic distortions and issues occurring upon interface formation are detrimental for the photovoltaic performance of perovskite solar cells. Herein, we incorporated a series of carbamide molecules (urea, biuret, or triuret) consisting of both Lewis base (–NH2) and Lewis acid (–C=O) groups into the perovskite precursor to simultaneously eliminate the bulk and interface defects. Depending on the different coordination ability with perovskite component, the incorporated molecules can either modify crystallization dynamics allowing for large crystal growth at low temperature (60°C), associate with antisite or undercoordinated ions for defect passivation, or accumulate at the surface as an energy cascade layer to enhance charge transfer, respectively. Synergistic benefits of the above functions can be obtained by rationally optimizing additive combinations in an all-in-one deposition method. As a result, a champion efficiency of 21.6% with prolonged operational stability was achieved in an inverted MAPbI3 perovskite solar cell by combining biuret and triuret additives. The simplified all-in-one fabrication procedure, adaptable to different types of perovskites in terms of pure MAPbI3, mixed perovskite, and all-inorganic perovskite, provides a cost-efficient and reproducible way to obtain high-performance inverted perovskite solar cells.

The emerging inorganic CsPbI2Br perovskite is regarded as a promising candidate for future photovoltaics due to its superior photo-physical property and thermal stability, but it usually requires a high fabrication...