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Solvent engineering and antisolvent methods have been used extensively to achieve high-quality, homogeneous, and crystalline perovskite thin films. Usually, highly concentrated (>1.1 M) precursor solutions are used to achieve the maximum power conversion efficiency (PCE), and most fabrication studies focus on iodide-based metal halide perovskites (MHPs). However, high concentrations of precursors are not suitable for semitransparent (ST) MHP solar cells (STPSCs), which require thinner films to achieve a high average visible transmittance (AVT). The deposition of high-quality perovskites with variable concentrations in a one-step method is challenging due to the complexity of the antisolvent crystallization process. Here, we have developed an in situtechnique based on photoluminescence (PL) measurements to identify the optimum delay time for antisolvent crystallization in formamidinium lead bromide (FAPbBr3). By monitoring the in situPL, the nucleation, crystal growth, and early perovskite formation phases are easily identified for a range of concentrations. Subsequently, we fabricated opaque and ST solar cells with optically clear, ST perovskite films formed from precursors with varying concentrations. These all-solution-processed STPSCs achieved AVTs of up to 35.6, 42.5, and 49.2%, with the corresponding PCEs of 5.71, 3.25, and 1.86% in p–i–n type, FAPbBr3perovskite solar cells with transparent Ag nanowire electrodes. These devices show good stability over several weeks and an impressive Vocas high as 1.24 V for STPSCs and 1.38 V for opaque cells produced with a thick Ag electrode. This work demonstrates the potential use of in situspectroscopy to tailor the film growth of halide perovskites with varying concentrations and the feasibility of using wide-band-gap perovskites for ST solar cells with exceptional clarity and higher Voc.

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.

Lead halide perovskite nanocrystals (NCs) have shown remarkable properties for emission applications, but their toxicity and instability are a hindrance to many commercial uses. Herein, we report the synthesis of lead-free all-inorganic Cs3Cu2X5(X = I, Br/I, Br, Br/Cl, Cl) colloidal nanocrystals as members of the metal–metal halide family of materials. These nanocrystals have uniform sizes less than 10 nm in diameter and show excellent optical properties, including composition-tunable emission spectra over the spectral region of 440–530 nm; high photoluminescence quantum yields of ∼100, 20, and 30% for X = Cl, Br, and I, respectively; and large effective Stokes shifts of over 100 nm for all species. Nanocrystals are synthesized by a room temperature, antisolvent method, but the precursors and ligands are also shown to be effective in hot -injection synthesis. Pure- and mixed-halide materials show tunable emission with the halide concentration, with a large fwhm of 80–110 nm due to a widely reported exciton self-trapping emission mechanism. Notably, the Cu3Cu2Cl5NCs exhibit a near-unity quantum yield with an emission at 520 nm, high crystallinity, and good stability. These materials can be processed and maintained in adequately stable dispersions to enable inkjet printing of these materials into arbitrary patterns. These results indicate that cesium copper chloride NCs may have great potential for the future display or lighting applications.

Tandem cells are one of the most effective ways of breaking the single junction Shockley–Queisser limit. Solution-processable phosphate-buffered saline (PbS) quantum dots are good candidates for producing multiple junction solar cells because of their size-tunable band gap. The intermediate recombination layer (RL) connecting the subcells in a tandem solar cell is crucial for device performance because it determines the charge recombination efficiency and electrical resistance. In this work, a solution-processed ultrathin NiO and Ag nanoparticle film serves as an intermediate layer to enhance the charge recombination efficiency in PbS QD dual-junction tandem solar cells. The champion devices with device architecture of indium tin oxide/S–ZnO/1.45 eV PbS–PbI2/PbS–EDT/NiO/Ag NP/ZnO NP/1.22 eV PbS–PbI2/PbS–EDT/Au deliver a 7.1% power conversion efficiency, which outperforms the optimized reference subcells. This result underscores the critical role of an appropriate nanocrystalline RL in producing high-performance solution-processed PbS QD tandem cells.

Ruddlesden–Popper phase inorganic metal halide perovskites are promising candidates for efficient light-emitting diodes (LEDs) with high brightness and color purity. Here, we demonstrate LEDs made from in situ grown CsPbX3quasi 2D/3D thin films that are color tunable across the entire visible spectrum. CsPbX3nanosheets are used to produce RP phase perovskites using butylammonium as a separating ligand to create BA2Csn–1Pbn(Br/Y)3n+12D/3D mixed halide thin films, where Y = Cl or I. The number of CsPbBr3monolayers in these crystals was optimized by changing the butylammonium concentration. We demonstrate a stable perovskite phase with thin emission line widths providing points covering the edge of the CIE triangle and a maximum red/green/blue coverage of ∼130% of the National Television System Committee color standard. Additionally, we are able to report record efficiencies for blue emitting perovskite nanocrystal LEDs with a maximum external quantum efficiency (EQE) of 2.4% and 6.2% at 465 and 487 nm and a maximum luminance of 3340 cd/m2. We also demonstrate efficient green LEDs with a maximum efficiency of 10.1% EQE, 23.3 cd/A and 9.8 lm/W at 16.3 mA/cm2.

Solution-processed semiconductor nanocrystals are evolving as potential candidates for future display and lighting applications owing to their size-tunable emission, ultrasaturated colors, and compatibility with large-area flexible substrates. Among them, quantum rods (QRs) are emerging materials for optoelectronic applications, offering polarized emission, high light outcoupling efficiency, color purity, and better stability in solid films. However, synthesizing QRs covering the full visible wavelength region has been a big challenge, particularly in the blue range. Herein, we report for the first time the synthesis of red CdSe/CdS, green CdSe/ZnxCd1–xS/ZnS, and blue CdSe/ZnxCd1–xS/ZnS QRs and their application in red, green, and blue QR-based light-emitting diodes (QR-LEDs). We have improved the charge injection balance into the QRs through embedding a poly(methyl methacrylate) (PMMA) layer between the emissive and electron transport layers. The thin PMMA electron-blocking layer (EBL) suppresses the excessive electron flux and thus promotes charge injection balance and pushes the recombination zone back to the QR layer, resulting in 1.35×, 1.2×, and 1.7× peak external quantum efficiency improvement for red, green, and blue QR-LEDs, respectively. The efficiency roll-off of green and blue QR-LEDs with an EBL is less than 50% at maximum current density. The proposed red, green, and blue QR-LEDs open up an avenue toward further improving the light source efficiency and stability focusing on real device applications.

AgBiS2nanocrystals are a promising nontoxic alternative to PbS, CsPbI3, and CdS quantum dots for solution-fabricated nanocrystal photovoltaics. In this work, we fabricated the first inverted (p–i–n) structure AgBiS2nanocrystal 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/AgBiS2interfaces and demonstrated that the NiO/AgBiS2NC 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 (JSC) over 20.7 mA cm–2and 0.38 V open-circuit voltage (VOC), suggesting their potential for further improvements in efficiency and, eventually, for large-scale production.