Developing low-cost, efficient, and stable photocatalysts is one of the most promising methods for large-scale solar water splitting. As a metal-free semiconductor material with suitable band gap, graphitic carbon nitride (g-C₃N₄) has attracted attention in the field of photocatalysis, which is mainly attributed to its fascinating physicochemical and photoelectronic properties. However, several inherent limitations and shortcomings—involving high recombination rate of photocarriers, insufficient reaction kinetics, and optical absorption—impede the practical applicability of g-C₃N₄. As an effective strategy, vacancy defect engineering has been widely used for breaking through the current limitations, considering its ability to optimize the electronic structure and surface morphology of g-C₃N₄ to obtain the desired photocatalytic activity. This review summarizes the recent progress of vacancy defect engineered g-C₃N₄ for solar water splitting. The fundamentals of solar water splitting with g-C₃N₄ are discussed first. We then focus on the fabrication strategies and effect of vacancy generated in g-C₃N₄. The advances of vacancy-modified g-C₃N₄ photocatalysts toward solar water splitting are discussed next. Finally, the current challenges and future opportunities of vacancy-modified g-C₃N₄ are summarized. This review aims to provide a theoretical basis and guidance for future research on the design and development of highly efficient defective g-C₃N₄.

Despite that organic-inorganic lead halide perovskites have attracted enormous scientific attention for energy conversion applications over the recent years, the influence of temperature and the type of the employed hole transport layer (HTL) on the charge carrier dynamics and recombination processes in perovskite photovoltaic devices is still largely unexplored. In particular, significant knowledge is missing on how these crucial parameters for radiative and non-radiative recombinations, as well as for efficient charge extraction vary among different perovskite crystalline phases that are induced by temperature variation. Herein, we perform micro photoluminescence (μPL) and ultrafast time resolved transient absorption spectroscopy (TAS) in Glass/Perovskite and two different Glass/ITO/HTL/Perovskite configurations at temperatures below room temperature, in order to probe the charge carrier dynamics of different perovskite crystalline phases, while considering also the effect of the employed HTL polymer. Namely, CH₃NH₃PbI₃ films were deposited on Glass, PEDOT:PSS and PTAA polymers, and the developed Glass/CH₃NH₃PbI₃ and Glass/ITO/HTL/CH₃NH₃PbI₃ architectures were studied from 85 K up to 215 K in order to explore the charge extraction dynamics of the CH₃NH₃PbI₃ orthorhombic and tetragonal crystalline phases. It is observed an unusual blueshift of the bandgap with temperature and the dual emission at temperature below of 100 K and also, that the charge carrier dynamics, as expressed by hole injection times and free carrier recombination rates, are strongly depended on the actual pervoskite crystal phase, as well as, from the selected hole transport material.Despite that organic-inorganic lead halide perovskites have attracted enormous scientific attention for energy conversion applications over the recent years, the influence of temperature and the type of the employed hole transport layer (HTL) on the charge carrier dynamics and recombination processes in perovskite photovoltaic devices is still largely unexplored. In particular, significant knowledge is missing on how these crucial parameters for radiative and non-radiative recombinations, as well as for efficient charge extraction vary among different perovskite crystalline phases that are induced by temperature variation. Herein, we perform micro photoluminescence (μPL) and ultrafast time resolved transient absorption spectroscopy (TAS) in Glass/Perovskite and two different Glass/ITO/HTL/Perovskite configurations at temperatures below room temperature, in order to probe the charge carrier dynamics of different perovskite crystalline phases, while considering also the effect of the employed HTL polymer. Namely, CH₃NH₃PbI₃ films were deposited on Glass, PEDOT:PSS and PTAA polymers, and the developed Glass/CH₃NH₃PbI₃ and Glass/ITO/HTL/CH₃NH₃PbI₃ architectures were studied from 85 K up to 215 K in order to explore the charge extraction dynamics of the CH₃NH₃PbI₃ orthorhombic and tetragonal crystalline phases. It is observed an unusual blueshift of the bandgap with temperature and the dual emission at temperature below of 100 K and also, that the charge carrier dynamics, as expressed by hole injection times and free carrier recombination rates, are strongly depended on the actual pervoskite crystal phase, as well as, from the selected hole transport material.

Optoelectronic applications based on the perovskites always face challenges due to the inherent chemical composition volatility of perovskite precursors. The efficiency of perovskite-based light-emitting diodes (Pe-LEDs) can be enhanced by improving the perovskite film via solvent engineering. A dual solvent post-treatment strategy was applied to the perovskite film, which provides a synchronous effect of passivating surface imperfections and reduces exciton quenching, as evidenced by improved surface morphology and photoluminance. Thus, the optimized Pe-LEDs reach 17,866cd·m-2 maximum brightness, 45.8cd·A-1 current efficiency, 8.3% external quantum efficiency, and relatively low turn-on voltage of 2.0 V. Herein, we present a simple technique for the fabrication of stable and efficient Pe-LEDs.