Tin selenide (SnSe) is a sustainable, lead-free IV–VI semiconductor whose layered orthorhombic crystal structure induces pronounced electronic and phononic anisotropy, enabling diverse energy-related functionalities. This review systematically summarizes recent progress in understanding the structure–property–processing relationships that govern SnSe performance in thermoelectric and optoelectronic applications. Key crystallographic characteristics are first discussed, including the temperature-driven Pnma–Cmcm phase transition, anisotropic band and valley structures, and phonon transport mechanisms that lead to intrinsically low lattice thermal conductivity below 0.5 W m⁻¹ K⁻¹ and tunable carrier transport. Subsequently, major synthesis strategies are critically compared, spanning Bridgman and vertical-gradient single-crystal growth, spark plasma sintering and hot pressing of polycrystals, as well as vapor- and solution-based thin-film fabrication, with emphasis on process windows, stoichiometry control, defect chemistry, and microstructure engineering. For thermoelectric applications, directional and temperature-dependent transport behaviors are analyzed, highlighting record thermoelectric performance in single-crystal SnSe at hi. We analyze directional and temperature-dependent transport, highlighting record thermoelectric figure of merit values exceeding 2.6 along the b-axis in single-crystal SnSe at ~900 K, as well as recent progress in polycrystalline and thin-film systems through alkali/coinage-metal doping (Ag, Na, Cu), isovalent and heterovalent substitution (Zn, S), and hierarchical microstructural design. For optoelectronic applications, optical properties, carrier dynamics, and photoresponse characteristics are summarized, underscoring high absorption coefficients exceeding 10⁴ cm⁻¹ and bandgap tunability across the visible to near-infrared range, together with interface engineering strategies for thin-film photovoltaics and broadband photodetectors. Emerging applications beyond energy conversion, including phase-change memory and electrochemical energy storage, are also reviewed. Finally, key challenges related to selenium volatility, performance reproducibility, long-term stability, and scalable manufacturing are identified. Overall, this review provides a process-oriented and application-driven framework to guide the rational design, synthesis optimization, and device integration of SnSe-based materials.

As a core candidate material for indium-free transparent conductive oxides, tin dioxide (SnO₂) thin films are gradually replacing indium tin oxide (ITO) and becoming a research focus in the field of optoelectronic devices, thanks to their excellent physicochemical stability, wide bandgap characteristics, and abundant tin resource reserves. This review focuses on SnO₂ thin films. Firstly, it elaborates on the tetragonal rutile crystal structure characteristics of SnO₂ and the transparent conductive mechanism based on oxygen vacancies and doping elements to regulate free electron concentration, while clarifying the key parameters for evaluating their transparent conductive properties. Subsequently, it systematically summarizes the research progress in preparing SnO₂ transparent conductive thin films via physical methods and chemical methods in recent years. It compares the microstructure and transparent conductive properties of thin films prepared by different methods, and analyzes the regulatory laws of preparation processes, doping types, and film thickness on their optoelectronic properties. Furthermore, this work supplements the current application status of SnO₂ thin films in devices. Meanwhile, the core performance differences between indium-free tin-based thin film devices and ITO-based devices are compared. Finally, we have summarized the advantages and challenges of physical and chemical methods in the preparation of SnO₂ thin films. It also forecasts the application potential of interdisciplinary integration of physical–chemical methods and the development of new doping systems in the preparation of high-performance SnO₂ transparent conductive thin films. This review aims to provide theoretical guidance and technical references for the selection and process optimization of SnO₂ transparent conductive thin films in fields such as photovoltaic devices and flexible optoelectronic equipment.

With the increasingly prominent issues of energy shortage and environmental pollution, the development of clean energy materials has become a core topic in the academic community. SnSe, as a material with moderate bandgap, a high light absorption coefficient, and environmental friendliness, has shown broad application prospects in the fields of photovoltaics and thermoelectrics. However, pure SnSe thin films have inherent defects, low carrier concentration, and high recombination rates, which limit their photoelectric conversion efficiency. This article provides a detailed overview of the characteristics of band engineering control technology, defect control technology, and carrier concentration control technology, as well as the improvements in the characteristics of SnSe thin films that they bring. This article systematically reviews the research progress on doping control technology for SnSe thin films characteristics in recent years and analyzes and discusses the differences in typical doping elements on SnSe thin films characteristics, such as optical bandgap and absorption coefficient, and applicable application scenarios, such as photovoltaics, near-infrared/infrared detection, and thermoelectric and flexible optoelectronic devices. Furthermore, the interaction between the doping mechanism of dopants and natural defects, as well as the influence of the structural parameters of doped films on doping efficiency, were analyzed, and a predictive design route for the doping mechanism of SnSe films was proposed. Finally, the influence of different atomic fractions on the characteristics of SnSe thin films was discussed. Low atomic fractions are beneficial for bandgap tuning and absorption enhancement; high atomic fractions can easily introduce phase separation and non-radiative recombination. It is suggested that future researchers can continue to focus on the precise control of atomic fractions, exploration of new element co-doping, and industrial large-scale production applications, providing theoretical guidance for the design and application of SnSe thin films in photothermal devices.

Transparent conductive oxides (TCOs) are indispensable core materials for optoelectronic devices, yet the inherent conflict between electrical conductivity and optical transparency, along with the scarcity and brittleness of indium tin oxide (ITO), severely limits their sustainable development. This review systematically summarizes the research progress of next-generation TCOs, focusing on microstructural engineering, advanced doping strategies, and architectural innovation to decouple the conductivity–transparency trade-off. The fundamental mechanisms of carrier scattering (ionized impurity scattering, grain boundary scattering) and the mobility-centric design paradigm are elaborated. The research status of typical material systems (SnO₂-based, ZnO-based, In₂O₃-based) is analyzed, and the mechanisms of high-valent cation doping, interstitial doping, and critical nucleation in optimizing carrier mobility are clarified. The oxide/metal/oxide (OMO) multilayer architecture is highlighted as a breakthrough strategy for synergistic optoelectronic performance. Current challenges including thermal stability, large-area fabrication, and environmental reliability are discussed, and future directions such as resonant doping, machine learning-assisted optimization, and multifunctional integration are prospected. This work provides a systematic theoretical basis and technical reference for the development of high-performance, sustainable TCOs.

Copper selenide (Cu₂Se), as a typical p-type narrow bandgap semiconductor, has garnered significant attention in the fields of thermoelectrics and optoelectronics due to its inherent low thermal conductivity, high Seebeck coefficient, low cost, and environmental friendliness. Compared with bulk materials, Cu₂Se thin films exhibit unique advantages in microdevice integration and flexible applications, holding great potential for applications in flexible thermoelectric generators, solar cells, and photodetectors. This article systematically reviews the research progress of Cu₂Se thin films, focusing on key preparation parameters such as growth temperature, annealing conditions, copper/selenium element ratio, and substrate type, and elucidates their regulation of film microstructure, crystal phase structure, and thermoelectric/optoelectronic properties. It delves into the mechanisms of doping strategies such as carrier concentration regulation, band engineering, and defect modification, clarifying the synergistic optimization effects of different doping elements on conductivity, Seebeck coefficient, and thermal conductivity. The article summarizes the current application status of Cu₂Se thin films, points out existing challenges such as poor process reproducibility and insufficient thermal stability, and anticipates future research directions such as multi-parameter synergistic optimization and heterojunction design, providing a systematic reference for the development and practical application of high-performance Cu₂Se-based functional thin films.