Multiple-cation lead mixed-halide perovskites (MLMPs) have been recognized as ideal candidates in perovskite solar cells in terms of high efficiency and stability due to decreased open-circuit voltage loss and suppressed yellow phase formation. However, they still suffer from an unsatisfactory long-term moisture stability. In this study, phosphorus-containing Lewis acid and base molecules are employed to improve device efficiency and stability based on their multifunction including recombination reduction, phase segregation suppression, and moisture resistance. The strong fluorine-containing Lewis acid treatment can achieve a champion PCE of 22.02%. Unencapsulated and encapsulated devices retain 63% and 80% of the initial efficiency after 14 days of aging under 75% and 85% relative humidity, respectively. The better passivation of Lewis acid implies more halide defects than Pb defects at the MLMP surface. This unbalanced defect type results from phase segregation that is the synergistic effect of Cs and halide ion migrations. Identifying defect type based on different passivation effects is beneficial to not only choose suitable passivators to boost the efficiency and slow down the moisture degradation of MLMP solar cells, but also to understand the mechanism of defect-assisted moisture degradation.

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Lead halide perovskite quantum dots (PQDs) are reported as a promising branch of perovskites, which have recently emerged as a field in luminescent materials research. However, before the practical applications of PQDs can be realized, the problem of poor stability has not yet been solved. Herein, we propose a trioctylphosphine (TOP)-assisted pre-protection low-temperature solvothermal synthesis of highly stable CsPbBr 3 /TiO 2 nanocomposites. Due to the protection of branched ligands and the lower temperature of shell formation, these TOP-modified CsPbBr 3 PQDs are successfully incorporated into a TiO 2 monolith without a loss of fluorescence intensity. Because the excellent nature of both parent materials is preserved in CsPbBr 3 /TiO 2 nanocomposites, it is found that the as-prepared CsPbBr 3 /TiO 2 nanocomposites not only display excellent photocatalytic activity but also yield improved PL stability, enabling us to build highly stable white light-emitting diodes and to photodegrade rhodamine B.

main obstacles to speed up their commercialization. [1][2][3] At present, polymer coating fluorescent lamp is the primary choice. However, commercial Philips yellow lamp can only filter UV light below 420 nm, of which cutoff wavelength is expected to extend to 500 nm, and decreased greenred emission intensities are inevitable due to the transparency limitation of filter polymer. Therefore, developing broadband yellow phosphors with a large full width at half-maximum (FWHM) is hopeful to increase cutoff wavelength and not scarify green-red dual emissions.Lead halide perovskites have excellent luminescent properties, including high photoluminescence quantum yield (PLQY) and adjustable luminescence peak positions, which have great potential for applications in photoluminescence and electroluminescence LEDs. [4][5][6][7] Quantum dots (QDs) and 2D perovskites can achieve quantum confinement via size effect and crystal structure respectively, which can improve the exciton binding energy contributing to the radiative recombination luminescence. [8][9][10][11][12] However, their excellent photoluminescence (PL) properties are easily lost when they are exposed to high humidity, high temperature, or high light illumination. [13][14][15][16] High binding ligands, inorganic core-shell structures, and polymer complexes are commonly used to improve the PL stability of perovskite QDs. [17][18][19] In particular, perovskite-polymer composite films can be prepared in a large area to achieve the display application. Ex situ method is mixing perovskite QDs and polymer in a nonpolar solvent, and nonuniform dispersion often occurs after solvent evaporation due to the absence of strong chemical interaction between perovskite and polymer. [20] By contrast, in situ method can achieve perovskite crystallization in polymer, which is beneficial to achieve more uniform composites and improve stability due to their enhanced interaction. [21][22][23] For example, Zhong et al. prepared the composite film of MAPbBr 3 QDs embedded in polyvinylidene fluoride (PVDF) by in situ method. The high PLQY of 94.6% and improved water and UV radiation stabilities were obtained due to the strong interaction between NH 3 + in perovskite and CF 2 groups in PVDF. [14] Furthermore, they prepared γ-Rb x Cs 1−x PbI 3 QDs-PMMA composite film with a PLQY of 91%, and it still maintained more than 95% intensity after 1000 h of industrial aging to overcome perovskite "red wall" issue. [24] 2D metal halide perovskites have emerged as highly bright and stable light emitters, which can be employed as phosphors for optically pumped luminescence devices. However, the intrinsic volatile property is the main weakness to achieve their long-term lighting applications. Here, an in situ doctor blade method is developed to fabricate a flexible large-area (20 × 25 cm 2 ) PEA 2 PbI 4 :2Mn-PVDF film with green-red dual emissions. Under UV lightemitting diode (LED) excitation, this yellow phosphor device shows a maximum luminance value of 250 cd m −2 , an extremely large full width a...

Very recently, ultrathin perovskite nanostructures, taking the advantages of perovskite as well as the ultrathin properties, have received an enormous level of interest due to their many fascinating properties, such...

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Multiple-cation lead mixed-halide perovskites (MLMPs) with tunable band gaps have been demonstrated as ideal candidates to achieve perovskite solar cells with high efficiencies. It is well-known that a large open-circuit voltage (V OC) loss caused by nonradiative recombination still limits the approach to the Shockley–Queisser limit. However, there are few comprehensive contributions regarding the origin and pathway of nonradiative recombination in n-i-p structured MLMPs. Here, we compare the performance of MLMPs containing different halides and analyze the energy loss and interface trap-assisted nonradiative recombination characterizations. It is found that Br-containing devices with a lower interface trap density of 3.2 × 1013 cm–2 obtain a high V OC of 1.12 V, a small energy loss of 0.02 eV, radiative recombination current density of 8.05 × 10–21 A m–2, and total recombination current density of 22.16 mA cm–2. This work provides an opportunity to understand the device physics and reveals the nature of nonradiative recombination based on experiment and simulation.