Copper zinc tin sulfur selenide (Cu₂ZnSn(S,Se)₄, CZTSSe) thin-film solar cells have emerged as a promising photovoltaic technology due to their environmentally benign composition and abundant elemental constituents, though their current efficiency record remains constrained by substantial open-circuit voltage losses at the heterojunction interface. This review systematically examines the crucial role of heterojunction annealing processes in enhancing device performance, demonstrating that precisely optimized annealing parameters can effectively promote interfacial element redistribution, improve band alignment, and significantly suppress recombination losses. The low-temperature prolonged annealing approach has proven particularly effective in achieving superior interface passivation while maintaining structural integrity. Further interface optimization has been realized through innovative strategies including nanoscale interlayer engineering and cationic substitution approaches. By comprehensively analyzing recent advances in heterojunction annealing technology and highlighting promising research directions such as atomic-scale interface modification and computational optimization methods, this work provides valuable insights for overcoming the efficiency limitations of CZTSSe solar cells and advancing their commercial potential.

Photothermal conversion efficiency and biocompatibility are two valuable factors of photothermal agents for photothermal therapy of tumors. However, the synthesis of efficient photothermal agents with desired biocompatibility remains a great challenge in the green synthesis due to harsh reaction conditions of existing methods. Herein, a green and facile biosynthetic method for preparing the photothermal agent (PTA) copper sulfide by cell-regulated was reported for the first time. The intracellular CuS nanoaggregates (nCuS) are biosynthesized using yeast cells as bioreactors and the functional yeast cells including the intercellular bio-PTA with photothermal effect are constructed (nCuS@yeast). The biomolecules derived from the yeast cells are used as conditioning and stabilizing mediator to regulate the biosynthesis of the nCuS. The biosynthetic nCuS exhibits a good biocompatibility and a high photothermal conversion efficiency (45.24%). Additionally, the absorption of internal nCuS in the near-infrared region is not affected by the cell wall, which is beneficial for photothermal therapy. In vitro and in vivo studies reveal the great potential of nCuS@yeast in tumor photothermal therapy. This research establishes a new and green avenue for the synthesis of biocompatible photothermal nanomaterials through a cell-based biosynthesis strategy, highlighting its potential application in the field of tumor therapy.

Due to the inherent toxicity of lead (Pb) and the severe structural instability of lead halide perovskites (LHPs), the advancement of LHPs solar cells (LHPSCs) has been significantly impeded. Consequently, the search for environmentally friendly alternative materials has become a key focus of current research. Bismuth (Bi) halide perovskites (BHPs) have gained considerable attention as viable alternatives in photovoltaic (PV) applications owing to their lower toxicity, excellent PV performance, and tunable structural properties. This review categorizes BHPs based on their elemental composition into ternary A_aBi_bX_a+3b (A = MA⁺, FA⁺, Ag⁺, Cu⁺, Cs⁺; X = Br⁻, Cl⁻, I⁻) and quaternary A₂AgBiX₆ (A = Cs⁺, Cu⁺; X = Br⁻, Cl⁻, I⁻) structures, as well as Cu_aAg_bBi_cI_d, and presents a detailed overview of the current research progress and future development prospects of these materials in the field of solar cells. Furthermore, strategies for preparing high-performance BHP solar cells (BHPSCs) are summarized, addressing aspects such as fabrication process, component engineering and additive engineering, interface modification and device structure optimization. Through this review, we strive to establish a systematic framework for a comprehensive understanding of the current research on BHPs and their potential applications in PV field, and offer reference and guidance for future research and development.

Silver sulfide (Ag₂S) is one of the best photovoltaic materials in terms of elemental composition and both chemical stability and device stability. However, the lack of suitable film processing methods severely limits the power conversion efficiency (PCE) improvement of Ag₂S-based devices. Here, we propose a specific solvent engineering train for high-quality Ag₂S absorber films by precisely tuning the dimethyl sulfoxide (DMSO)/N,N-dimethylformamide (DMF) constituent and post-deposition annealing temperature. A preferential transition in crystal orientation from (012) to ( $\overline{1}03$) crystal planes is found to play a key role in photo-induced carrier behavior. The film surface morphology and grain size are fine-tuned, while the bulk defect concentration and mitigated interface carrier recombination are well suppressed. The optimized simple indium tin oxide (ITO)/Ag₂S/2,2’,7,7’-tetrakis(N,N-di-p-methoxyphenylamine)-9,9’-spirobifluorene (Spiro-OMeTAD)/Au device exhibits a significant increase in PCE from 0.77% to 2.57%, which is currently the highest value among the reported literatures of Ag₂S solar cells without an electron transport layer.