Solution-Processed Bismuth Halide Perovskite Thin Films: Influence of Deposition Conditions and A-Site Alloying on Morphology and Optical Properties

Influence of interaction between organic cation and inorganic unit in bi-based hybrid perovskites for photoelectronic properties

With the increase of the passion on lead-free perovskites, more and more endeavor focused on halobismuthates. Here, we have introduced the p-iodoaniline and p-phenylenediamine into Bi-based hybrid materials, and two photoactive iodobismuthate named p-phenylenediamine iodobismuthate (PDABI) and p-iodoaniline iodobismuthate (PIDBI) were prepared. Their single structures, band gaps, thermostability and other properties were explored. The structure results revealed that they all have 1D BiI₄ ^- anion chains with edge-shared BiI₆ octahedron. The DFT result revealed that PIDBI had an inherent interaction between the I substituent in p-iodoaniline cation and the Bi atom in inorganic BiI₄ ^- anion chains. The photodetector assembled by PDABI and PIDBI revealed that the interaction provided by symmetric p-phenylenediamine has a positive effect on PIDBI's optoelectronic properties compared to the role of asymmetric p-iodoaniline in PDABI.

Lead-Free Halide Perovskites for Light Emission: Recent Advances and Perspectives

Lead-based halide perovskites have received great attention in light-emitting applications due to their excellent properties, including high photoluminescence quantum yield (PLQY), tunable emission wavelength, and facile solution preparation. In spite of excellent characteristics, the presence of toxic element lead directly obstructs their further commercial development. Hence, exploiting lead-free halide perovskite materials with superior properties is urgent and necessary. In this review, the deep-seated reasons that benefit light emission for halide perovskites, which help to develop lead-free halide perovskites with excellent performance, are first emphasized. Recent advances in lead-free halide perovskite materials (single crystals, thin films, and nanocrystals with different dimensionalities) from synthesis, crystal structures, optical and optoelectronic properties to applications are then systematically summarized. In particular, phosphor-converted LEDs and electroluminescent LEDs using lead-free halide perovskites are fully examined. Ultimately, based on current development of lead-free halide perovskites, the future directions of lead-free halide perovskites in terms of materials and light-emitting devices are discussed.

Alkali-metal-ion-doping strategy to improve the photovoltaic properties of Ag2BiI5 solar cells

An efficient alkali-metal-ion-doping strategy is proposed to improve the photovoltaic properties of Ag₂BiI₅ solar cells.

Solvatochromic Photoluminescent Effects in All-Inorganic Manganese(II)-Based Perovskites by Highly Selective Solvent-Induced Crystal-to-Crystal Phase Transformations

The development of lead-free perovskite photoelectric materials has been an extensive focus in the recent years. Herein, a novel one-dimensional (1D) lead-free CsMnCl₃ (H₂ O)₂ single crystal is reported with solvatochromic photoluminescence properties. Interestingly, after contact with N,N-dimethylacetamide (DMAC) or N,N-dimethylformamide (DMF), the crystal structure can transform from 1D CsMnCl₃ (H₂ O)₂ to 0D Cs₃ MnCl₅ and finally transform into 0D Cs₂ MnCl₄ (H₂ O)₂ . The solvent-induced crystal-to-crystal phase transformations are accompanied by loss and regaining of water of crystallization, leading to the change of the coordination number of Mn²⁺ . Correspondingly, the luminescence changes from red to bright green and finally back to red emission. By fabricating a test-paper containing CsMnCl₃ (H₂ O)₂ , DMAC and DMF can be detected quickly with a response time of less than one minute. These results can expand potential applications for low-dimensional lead-free perovskites.

Large-Grained All-Inorganic Bismuth-Based Perovskites with Narrow Band Gap via Lewis Acid-Base Adduct Approach

Bismuth halide perovskites have recently been considered a potential alternative to lead halide analogues due to their low toxicity and high stability. However, the layered flake structure and wide band gap limit their applications in perovskite solar cells (PSCs). We herein show that large-grained all-inorganic bismuth-based perovskites with a narrow band gap can be obtained from a Lewis acid-base adduct reaction under ambient conditions. Thiourea (CH₄N₂S) is utilized as a Lewis base to interact with BiI₃, confirmed with infrared (IR) spectra. The strong coordination between thiourea and the Bi³⁺ center could slow down the perovskite crystallization and promote the preferred orientation of the perovskite crystals with a hexagonal phase. The morphology of the perovskite films varies dramatically with an increase of molar ratio of BiI₃ and thiourea in the precursor. The perovskites derived from a BiI₃/thiourea ratio of 1:2 display extrathick grains, higher surface coverage, extended light absorption, higher crystallinity, and similar air stability compared to the pristine sample. The power conversion efficiency (PCE) of the thiourea-induced bismuth perovskite solar cells is significantly enhanced due to the higher surface coverage and the broader absorption of the perovskite film.