Enhanced Photovoltaic Performance of BiSCl Solar Cells Through Nanorod Array

van der Waals Stacking-Determined Polymorphs of Quasi-One-Dimensional BiSCl Grown by Chemical Vapor Deposition

We report chemical vapor deposition (CVD) synthesis of two quasi-one-dimensional (quasi-1D) polymorphs of BiSCl, denoted by y-BiSCl and r-BiSCl. The length of the CVD samples can reach about 0.4 mm. Such quasi-1D samples of the two polymorphs can be readily separated into individual pieces for either characterization or application. The two polymorphs can be clearly differentiated by Raman spectroscopy. First-principles calculations and group analysis are used to assign each Raman peak to the corresponding vibrational mode. Ultraviolet-visible measurements on solution grown thin-film samples reveal that the two polymorphs exhibit significantly different band gaps of 2.08 eV (y-BiSCl) and 1.81 eV (r-BiSCl). First-principles calculation further shows that the interatomic chain binding energy is 18.1 meV/Å2, confirming that the van der Waals stacking determines the difference in their band gaps. Our findings highlight the possibility of realizing the desired functionalities in quasi-1D materials by controlling stacking orientation.

Growth of BiSBr Microsheet Arrays for Enhanced Photovoltaics Performance

In this study, single-crystalline BiSBr is synthesized using a solution-based approach and conducted a systematic characterization of its photoelectric properties and photovoltaic performances. UV photoelectron spectroscopy and density functional theory (DFT) calculations reveal that BiSBr is an indirect p-type semiconductor, characterized by distinct positions and compositions of the valence band maximum and conduction band minimum. The BiSBr single crystal microrod features a significant electrical conductivity of 14 800 S m-1 along the c-axis, denoting minimal carrier resistance in this direction. For photovoltaic performance assessment, the authors successfully fabricated two homogeneous BiSBr films on TiO2 porous substrates: A microsheet array film via physical vapor deposition (PVD) and solvothermal treatment, and a BiSBr microsheet film via PVD and thermal treatment. The solar cell, comprising a BiSBr microsheet array film with an architecture of fluorine-doped tin oxide FTO/TiO2/BiSBr/(I3 -/I-)/Pt, demonstrated a power conversation efficiency of 1.40%, ≈11 times that of BiSBr microsheet film counterpart. These preliminary results underscore the potential of BiSBr microsheet arrays, producible through low-cost solution processes, as adept light absorbers, enhancing photovoltaic efficiency through effective light scattering and promoting efficient electron-hole separation and transport.

Heavy pnictogen chalcohalides for efficient, stable, and environmentally friendly solar cell applications

Solar cell technology is an effective solution for addressing climate change and the energy crisis. Therefore, many researchers have investigated various solar cell absorbers that convert Sunlight into electric energy. Among the different materials researched, heavy pnictogen chalcohalides comprising heavy pnictogen cations, such as Bi³⁺and Sb³⁺, and chalcogen-halogen anions have recently been revisited as emerging solar absorbers because of their potential for efficient, stable, and low-toxicity solar cell applications. This review explores the recent progress in the applications of heavy pnictogen chalcohalides, including oxyhalides and mixed chalcohalides, in solar cells. We categorize them into material types based on their common structural characteristics and describe their up-to-date developments in solar cell applications. Finally, we discuss their material imitations, challenges for further development, and possible strategies for overcoming them.

Colloidal Bismuth Chalcohalide Nanocrystals

Here we present a colloidal approach to synthesize bismuth chalcohalide nanocrystals (BiEX NCs, in which E=S, Se and X=Cl, Br, I). Our method yields orthorhombic elongated BiEX NCs, with BiSCl crystallizing in a previously unknown polymorph. The BiEX NCs display a composition-dependent band gap spanning the visible spectral range and absorption coefficients exceeding 105  cm-1 . The BiEX NCs show chemical stability at standard laboratory conditions and form colloidal inks in different solvents. These features enable the solution processing of the NCs into robust solid films yielding stable photoelectrochemical current densities under solar-simulated irradiation. Overall, our versatile synthetic protocol may prove valuable in accessing colloidal metal chalcohalide nanomaterials at large and contributes to establish metal chalcohalides as a promising complement to metal chalcogenides and halides for applied nanotechnology.