The trap states at grain boundaries (GBs) within polycrystalline perovskite films deteriorate their optoelectronic properties, making GB engineering particularly important for stable high-performance optoelectronic devices. It is demonstrated that trap states within bulk films can be effectively passivated by semiconducting molecules with Lewis acid or base functional groups. The perovskite crystallization kinetics are studied using in situ synchrotron-based grazing-incidence X-ray scattering to explore the film formation mechanism. A model of the passivation mechanism is proposed to understand how the molecules simultaneously passivate the Pb-I antisite defects and vacancies created by under-coordinated Pb atoms. In addition, it also explains how the energy offset between the semiconducting molecules and the perovskite influences trap states and intergrain carrier transport. The superior optoelectronic properties are attained by optimizing the molecular passivation treatments. These benefits are translated into significant enhancements of the power conversion efficiencies to 19.3%, as well as improved environmental and thermal stability of solar cells. The passivated devices without encapsulation degrade only by ≈13% after 40 d of exposure in 50% relative humidity at room temperature, and only ≈10% after 24 h at 80 °C in controlled environment.

Solution-processed hybrid perovskite semiconductors attract a great deal of attention, but little is known about their formation process. The one-step spin-coating process of perovskites is investigated in situ, revealing that thin-film formation is mediated by solid-state precursor solvates and their nature. The stability of these intermediate phases directly impacts the quality and reproducibility of thermally converted perovskite films and their photovoltaic performance.

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Efficient and stable inorganic lead-free halide perovskites have attracted tremendous attention for next-generation solid-state lighting. However, single perovskite phosphors with strong, tunablecolor-temperature white-light emission are rare. Here, a doping strategy was developed to incorporate Sb 3+ and Bi 3+ ions into Cs 2 NaInCl 6 single crystals. Blue and yellow emission for white light with a 77% quantum yield was observed. The dual-emission originates from different [SbCl 6 ] 3− octahedron-related self-trapped excitons (STEs). The blue emission is attributable to limited Jahn−Teller deformation from Sb 3+ doping. Largeradii Bi 3+ increase the deformation level of the [SbCl 6 ] 3− octahedron, enhancing yellow STE emission. Density functional theory calculations indicated that the Bi 3+ doping forms a sub-band level, which produces yellow STE emission. Tuning between warm and cold white light can be realized by changing the Sb 3+ /Bi 3+ doping ratio, which suggests a unique interaction mechanism between Sb 3+ and Bi 3+ dopants, as well as Bi 3+ -induced lattice distortion in double perovskites.

Perovskite solar cells (PSCs) are ideally fabricated entirely via a scalable solution process at low temperatures to realize the promise of simple manufacturing, low‐cost processing, compatibility with flexible substrates, and perovskite‐based tandem solar cells. However, high‐quality photoactive perovskite thin films under those processing conditions is a challenge. Here, a laminar air‐knife‐assisted room‐temperature meniscus coating approach that enables one to control the drying kinetics during the solidification process and achieve high‐quality perovskite films and solar cells is devised. Moreover, this approach offers a solid model platform for in situ UV–vis and microscopic investigation of the perovskite film drying kinetics, which provide rich insights correlating the degree of supersaturation, the nucleation, and growth rate during the kinetic drying process, and ultimately, the film morphology and performance of the solar cell devices. Manufacturing friendly, antisolvent‐free room‐temperature coating of hysteresis‐free PSCs with a power conversion efficiency of 20.26% for 0.06 cm2 and 18.76% for 1 cm2 devices is demonstrated.