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Metal halide perovskites (MHPs) have emerged as promising next-generation optoelectronic materials and achieved remarkable performances in both light-emitting diodes (LEDs) and solar cells (SCs). Despite reaching market demands such as high efficiencies and low manufacturing cost, the long-term stability of MHPs is still a massive challenge for commercialization. The presence of surface and bulk defects due to low-temperature solution-processable methods causes past degradation of perovskites. Here, we have investigated the passivation strategy for methylammonium lead iodide (MAPbI3) using resin polymer poly-[(phenylglycidyl ether)-co-formaldehyde] (PCF). PCF acts as a Lewis base additive with an electron-donating oxygen atom, which can coordinate with undercoordinated Pb2+ ions or NH3+ in perovskite crystals, developing smaller nanocrystalline grains with reduced defects. As a result, the PCF-passivated samples exhibit improved stability against moisture in a humid ambient environment (RH > 70%). Moreover, enhanced photoluminescence (PL) and lifetime were achieved without encapsulation. Furthermore, LEDs are demonstrated using the optimized PCF content. These results show the importance of resin polymers, which performs multiple functionalities such as nanocrystalline grain formation, defect passivation, and stability improvements for optoelectronic devices. [ABSTRACT FROM AUTHOR]

Singlet fission is a process by which an organic semiconductor is able to generate two triplet excitons from a single photon. If charges from the triplets can be successfully harvested without heavy losses in energy, then this process can enable a single‐junction solar cell to surpass the Shockley–Queisser limit. While singlet fission processes are commonly observed in several materials, harvesting the resulting triplets is difficult and has been demonstrated with only a few transport materials. Here, transient absorption spectroscopy is used to investigate singlet fission and carrier transfer processes at the AgBiS2/pentacene (AgBiS2/Pc) heterojunction. The successful transfer of triplets from pentacene to AgBiS2 and the transfer of holes from AgBiS2 to pentacene is observed. Further singlet fission in pentacene by modifying the crystallinity of the pentacene layer and have fabricated the first singlet fission AgBiS2/Pc solar cell is enhanced. Singlet fission devices exhibit higher external quantum efficiency compared with the control devices, and thus demonstrating the significant contribution of charges from the singlet fission process. [ABSTRACT FROM AUTHOR]

CsPbX3 perovskite nanorods are known to display polarized emission, but also suffer from morphological and spectral instability. Here we synthesized CsPbX3 nanorods with polarized emission across the visible emission spectrum. We find that polarized emission is a function solely of the aspect ratio, as would be expected based on a purely dielectric effect. We then observe changes over time in the emission spectrum and polarization anisotropy as a function of the morphology. We find that, although these perovskite nanorods exhibit strongly polarized emission after synthesis, they suffer from serious morphological instability that reduces the polarization anisotropy over time. Worryingly, nanorods dispersed in anhydrous solvents, and even in a polymer matrix were observed to degrade in both inert environments and under ambient conditions. This results in a significant loss in polarized emission, and represents a problem for many intended applications. Finally, we evaluate several strategies for protecting these particles and find that silica encapsulation can be used to successfully prevent loss of polarized emission even under ambient conditions. [ABSTRACT FROM AUTHOR]

Quantum‐confined CsPbI3 perovskite nanoplatelets (NPLs) are highly desirable for optoelectronic applications owing to their anisotropic electronic properties that substantially boost the light outcoupling efficiency in light‐emitting diodes (LEDs). However, the structural instability of the emissive CsPbI3 phases makes it degrade rapidly to the non‐emissive δ‐phase under ambient conditions. Here, the study presents a synthetic approach to produce spectrally stable CsPbI3 nanoplatelets (NPLs) through solid‐phase crude reactions with metal iodide powders, MI2 (M2+ = Mn2+ or Zn2+). The synthesized NPLs exhibit narrow and color‐pure red emission with high photoluminescence (PL) quantum yields (QYs, ηPL) of up to 85%. Systematic investigations into the surface chemistry of NPLs reveal that metal iodide treatment stabilizes anisotropic CsPbI3 NPLs via surface passivation with metal and halide ions, substantially hindering from the formation of non‐emissive yellow phase. The anisotropic NPLs display signatures of spontaneous self‐assembly in spin‐casted films, which yield strong emission anisotropy, with up to 82% of the transition dipoles being horizontally oriented with respect to the substrate, as revealed by the back focal plane (BFP) imaging. The results presented here shed light on solid‐phase approaches for the preparation of quantum‐confined nanocrystals (NCs) with desirable geometry, which boost the light outcoupling efficiency in LEDs. [ABSTRACT FROM AUTHOR]

AgBiS 2 nanocrystals are a promising nontoxic alternative to PbS, CsPbI 3 , and CdS quantum dots for solution-fabricated nanocrystal photovoltaics. In this work, we fabricated the first inverted (p-i-n) structure AgBiS 2 nanocrystal solar cells. We selected spray-coated NiO as the hole-transporting material and used PCBM/BCP as the electron-transporting material. Combining transient photocurrent and photovoltage measurements with femtosecond transient absorption spectroscopy, we investigated the charge collection process on metal oxide/AgBiS 2 interfaces and demonstrated that the NiO/AgBiS 2 NC junction in the p-i-n configuration is more efficient for charge carrier collection. The fabricated p-i-n solar cells exhibited a 4.3% power conversion efficiency (PCE), which was higher than that of conventional n-i-p solar cells fabricated using the same sample. Additionally, inverted devices showed an ultrahigh short-circuit current ( J SC ) over 20.7 mA cm -2 and 0.38 V open-circuit voltage ( V OC ), suggesting their potential for further improvements in efficiency and, eventually, for large-scale production.

Materials that enable bifunctional operation in harvesting and storing energy are currently in high demand, due to their potential to efficiently use renewable solar energy. Here, we present a lead-free, all-inorganic, bismuth-based perovskite halide, which acts as a photoelectrode that can harvest energy under illumination without the assistance of an external load in a lithium-ion battery. The battery performance is shown using three different current collectors: copper, fluorine-doped tin oxide (FTO) and carbon felt (CF) to exhibit the electrode's function as a normal coin cell, as a basic photobattery with a transparent collector to elucidate its functional mechanism, and as an optimized photobattery displaying competitive metrics with other photobatteries obtaining a photo conversion efficiency of ∼0.43% for the first discharge. Upon discharging under illumination, we observed an increase in capacity from 410 to 975 mA·h·g -1 . Further exploration in anode structure and design provides a path toward more efficient photobatteries.