Here we report a solution-processing strategy to stabilize the perovskite-based heterostructure. Strong Pb–Cl and Pb–O bonds formed between a [CH(NH2)2]x[CH3NH3]1−xPb1+yI3 film with a Pb-rich surface and a chlorinated graphene oxide layer. The constructed heterostructure can selectively extract photogenerated charge carriers and impede the loss of decomposed components from soft perovskites, thereby reducing damage to the organic charge-transporting semiconductors. Perovskite solar cells with an aperture area of 1.02 square centimeters maintained 90% of their initial efficiency of 21% after operation at the maximum power point under AM1.5G solar light (100 milliwatts per square centimeter) at 60°C for 1000 hours. The stabilized output efficiency of the aged device was further certified by an accredited test center.

Inverted perovskite solar cells (IPSCs) have attracted great attention in recent years due to reliable operational stability, negligible hysteresis and low-temperature fabrication process. To accelerate its commercialization, the focus of...

Organic–inorganic hybrid perovskite solar cells (PSCs) are a promising photovoltaic technology that has rapidly developed in recent years. Nevertheless, a large number of ionic defects within perovskite absorber can serve as non‐radiative recombination center to limit the performance of PSCs. Here, organic donor‐π‐acceptor (D‐π‐A) molecules with different electron density distributions are employed to efficiently passivate the defects in the perovskite films. The X‐ray photoelectron spectroscopy (XPS) analysis shows that the strong electron donating N,N‐dibutylaminophenyl unit in a molecule causes an increase in the electron density of the passivation site that is a carboxylate group, resulting in better binding with the defects of under‐coordinated Pb2+ cations. Carrier lifetime in the perovskite films measured by the time‐resolved photoluminescence spectrum is also prolonged by an increase in donation ability of the D‐π‐A molecules. As a consequence, these benefits contribute to an increase of 80 mV in the open circuit voltage of the devices, enabling a maximum power conversion efficiency (PCE) of 20.43%, in comparison with PCE of 18.52% for the control device. The authors' findings provide a novel strategy for efficient defect passivation in the perovskite solar cells based on controlling the electronic configuration of passivation molecules.

All‐inorganic cesium lead iodide perovskites (CsPbI3) are promising wide‐bandgap materials for use in the perovskite/silicon tandem solar cells, but they easily undergo a phase transition from a cubic black phase to an orthorhombic yellow phase under ambient conditions. It is shown that this phase transition is triggered by moisture that causes distortion of the corner‐sharing octahedral framework ([PbI6]4−). Here, a novel strategy to suppress the octahedral tilting of [PbI6]4− units in cubic CsPbI3 by systematically controlling the steric hindrance of surface organic terminal groups is provided. This steric hindrance effectively prevents the lattice distortion and thus increases the energy barrier for phase transition. This mechanism is verified by X‐ray diffraction measurements and density functional theory calculations. Meanwhile, the formation of an organic capping layer can also passivate the surface electronic trap states of perovskite absorber. These modifications contribute to a stable power conversion efficiency (PCE) of 13.2% for the inverted planar perovskite solar cells (PSCs), which is the highest efficiency achieved by the inverted‐structure inorganic PSCs. More importantly, the optimized devices retained 85% of their initial PCE after aging under ambient conditions for 30 days.

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Lead‐free tin perovskite solar cells (TPSCs) have attracted widespread attention in recent years due to their low toxicity, suitable bandgap, and high carrier mobility. However, the photovoltage and efficiency of TPSCs are still much lower than those of the lead counterparts because of the high trap density and unfavorable band structure in tin perovskite films. To overcome these issues, efficient and stable TPSCs with a graded heterostructure of light‐absorbing layer are reported, in which the narrow‐bandgap tin perovskite dominates at the bulk, whereas the wide‐bandgap tin perovskite is distributed with a gradient from bulk to surface. This heterostructure can selectively extract the photogenerated charge carriers at the perovskite/electron transport layer interface, reduce the density of trap states, and impede the oxidation process of Sn2+ to Sn4+ in air. As a consequence, this graded heterostructure of tin perovskite layer contributes to an increase of 120 mV in the open‐circuit voltage and a maximum power conversion efficiency of 11% for TPSCs with longer operational stability.

Tin halide perovskites are promising candidates for preparing efficient leadfree perovskite solar cells due to their ideal band gap and high charge-carrier mobility. However, the notorious rapid crystallization process results in the inferior power conversion efficiency (PCE) of tin perovskite solar cells (TPSCs). Here, a facile method is employed to manage this crystallization process by using cold precursor solution that raises the critical Gibbs free energy to slow down the nucleation rate, sparing both space and time for crystal growth. In this way, highly oriented FASnI 3 films with micrometer-scale grains are fabricated and an increase of 70 mV in the open-circuit voltage is obtained for TPSCs. This method is compatible with other existed strategies such as additive engineering or the post-treatment method. The best-performing device that combines 0 °C precursor solution and post-treatment method demonstrates a PCE of 12.11%.

Perovskite solar cells (PSCs) have emerged as one of the third‐generation photovoltaic technologies. However, the toxicity issue of the lead element in perovskite absorbers hinders their large‐scale production. Thus, exploiting lead‐free perovskite materials becomes an important solution to overcome this challenge. Among all the candidates, tin perovskites have advanced rapidly in recent years due to their low toxicity, favorable bandgap, and high carrier mobility. After a few years of development, the highest power conversion efficiency (PCE) of tin PSCs has exceeded 13%, which is mainly attributed to the breakthroughs arising from additive engineering of the Sn perovskite layer. Herein, the role of additive engineering in the research community of tin PSCs is emphasized. First, the crystal structure, electronic characteristics, and the chemical instability of Sn perovskites are introduced. Next, additives used for stabilizing the Sn2+ components, purifying SnI2 sources, and improving the crystal quality of perovskite films are discussed in detail. Finally, challenges and perspectives are laid out to advance the properties of tin halide perovskites for further improving the device efficiency and stability.