The synthesis of stoichiometrically controlled quaternary chalcogenide nanoparticles through a simple, eco-friendly process is still a great challenge. Herein, earth-abundant quaternary chalcogenide nanoparticles, Cu₂FeSnS₄ (CFTS) and Cu₂CdSnS₄ (CCdTS), were synthesized via the thermal decomposition of metal precursors. The prepared CFTS and CCdTS films were used as alternative counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). The effects of the annealing atmosphere on morphology, elemental composition, electrical properties and electrochemical catalytic activity of the CFTS and CCdTS films were investigated. Energy dispersive spectroscopy, Hall measurements, cyclic voltammetry, and electrochemical impedance spectroscopy analysis demonstrate that the sulfurized CFTS and CCdTS-based CEs are more efficient for tri-iodide reduction as compared to the N₂-annealed CFTS and CCdTS-based CEs. The photoconversion efficiencies (PCEs) of DSSCs fabricated with sulfurized, annealed in N₂ atmosphere CFTS and CCdTS as CEs are found to 7.36 ± 0.00%, 5.78 ± 0.12% and 7.12 ± 0.08%, 5.30 ± 0.00% respectively, while the DSSCs fabricated with conventional Pt-based CEs show an efficiency of 8.15 ± 0.09%. These results indicate that the annealing atmosphere of the CEs has an impact on the DSSCs performance.

Indoor photovoltaics (IPVs) using low‐toxicity bismuth‐based perovskite‐inspired materials (PIMs) can potentially power the growing number of Internet of Things devices sustainably. However, modest indoor power conversion efficiency (PCE) values are reported due to intrinsic limitations of PIMs, particularly regarding charge carrier separation and transport. Herein, polycrystalline Cs₂AgBi₂I₉ thin films are developed with high phase purity and study their fundamental structural and photophysical properties. The comprehensive experimental and computational study reveals unique optoelectronic properties of Cs₂AgBi₂I₉ compared to other bismuth‐containing PIMs, including weak electron‐phonon coupling and low exciton binding energy (40 meV). This study also demonstrates the feasibility of large and highly mobile polaron formation in Cs₂AgBi₂I₉, supported by the observation of a phonon bottleneck and a delayed hot carrier lifetime of over 200 ps, which suggests enhanced defect tolerance and transport properties. Motivated by the suitable bandgap of this absorber (1.78 eV), the first Cs₂AgBi₂I₉‐based IPVs are developed, achieving a PCE of ≈8% at 1000 lux. Notably, the devices maintain high performance across various indoor environments with white LED color temperatures ranging from 2700 to 6500 K. The calculated theoretical PCE limit of >40% and the promising operational stability position Cs₂AgBi₂I₉ as one of the most intriguing candidates for sustainable IPVs.

The exponential increase in demand for global energy intake in day-to-day life directs us to look for a green and cost-effective energy generation and storage alternative. India being a fastly developing nation with a vast population, requires the alternative energy resource to meet up the energy deficit in an eco-friendly manner and be self-reliant in energy demands. This review aims to compile and assess developments in energy materials research from Indian prospects. Therefore, this paper discusses India’s energy scenario by understanding the fundamental concepts and developments of various solar cell technologies and an overview of energy storage systems (batteries and supercapacitors), accentuating the research progress made so far along with future possibilities. This exploratory study reviews the systematic and sequential advances in all three generations of the solar cell, i.e. Si solar cell, thin-film solar cell, dye-sensitized solar cell, and perovskite solar cells. Herein, the discussion is directed at developing novel materials that are efficient, stable, and economical. Moreover, the current status of the high-performance devices for each technology is reviewed in detail. Finally, the prospects, areas of improvement, and future trends in developing cost-effective and efficient energy materials for solar cells and storage devices are highlighted.