A comparative study of the mechanical stability, electronic, optical and photocatalytic properties of CsPbX3 (X = Cl, Br, I) by DFT calculations for optoelectronic applications

Modulating luminescence through anion variation in lead-free Cs2NaInX6 (X = Cl, Br, and I) perovskites: a first-principles study

The A2B+B'3+X6-type lead-free halide perovskite Cs2NaInCl6 has demonstrated limited luminescence performance attributed to parity-forbidden transitions in its intrinsic form. While extensive exploration has been dedicated to partial cation substitution in Cs2NaInCl6, there is a noticeable gap in understanding the impact of anion composition on this material. In this study, we investigated the influence of anion composition on the luminescence performance of Cs2NaInX6 using first-principles calculations. We first conducted calculations on Cs2NaInX6 in its intrinsic state and on Cs2NaInCl6 with cation substitution to establish the reliability of the transition dipole moment (TDM) as a luminescence descriptor in this system. Following this, we systematically assessed the formation energies, octahedral distortions, and luminescence properties of Cs2NaInX6 with diverse anion compositions. Despite sharing similar stability, closely aligned with the experimentally accessible Cs2NaInCl6, all mixed halide structures exhibited significant octahedral distortions. Additionally, most of these structures displayed considerably enhanced TDM compared to their single halide counterparts. Notably, the structures Cs2NaInX4X'2-b and Cs2NaInX3X'3-b demonstrated superior luminescence performance compared to other structures. The absorption spectra calculated for selected structures revealed the enhancement of their photo-absorbance in the presence of iodine, particularly in the low energy region. This observation provides additional evidence that light absorbance in different energy regions can be effectively regulated in this way. Finally, we also investigated other optical properties that impact luminescence performances, such as the energy loss spectrum L(ω), the reflectivity spectrum R(ω) and the refractivity index n(ω). The findings offer insights into optimizing the luminescence performance of lead-free halide perovskites through anion composition variation.

Design of highly selective and stable CsPbI3 perovskite catalyst for photocatalytic reduction of CO2 to C1 products

Finding efficient photocatalytic carbon dioxide reduction catalysts is one of the core issues in addressing global climate change. Herein, the pristine CsPbI3 perovskite and doped CsPbI3 perovskite were evaluated in carbon dioxide reduction reaction (CO2RR) to C1 products by using density functional theory. Free energy testing and electronic structure analysis methods have shown that doped CsPbI3 exhibits more effective catalytic performance, higher selectivity, and stability than undoped CsPbI3. Additionally, it is discovered that CsPbI3 (100) and (110) crystal surfaces have varied product selectivity. The photo-catalytic effectiveness is increased by the narrower band gap of Bi and Sn doped CsPbI3, which broadens the absorption spectrum of visible light and makes electron transport easier. The calculation results indicate that Bi doped CsPbI3 (100) and CsPbI3 (110) crystal faces exhibit good selectivity towards CH4, with free energy barriers as low as 0.55 eV and 0.58 eV, respectively. Sn doped CsPbI3 (100) and CsPbI3 (110) crystal planes exhibit good selectivity for HCOOH and CH3OH, respectively. The results indicate that the Bi and Sn doped CsPbI3 perovskite catalyst can further improve the CO2 photocatalytic activity and high selectivity for C1 products, making it a suitable substrate material for high-performance CO2RR.

Hydrogenation of CO2 into Value-added Chemicals Using Solid-Supported Catalysts

Reducing CO2 emissions is an urgent global priority. In this context, several mitigation strategies, including CO2 tax and stringent legislation, have been adopted to halt the deterioration of the natural environment. Also, carbon recycling procedures undoubtedly help reduce net emissions into the atmosphere, enhancing sustainability. Utilizing Earth's abundant CO2 to produce high-potential green chemicals and light fuels opens new avenues for the chemical industry. In this context, many attempts have been devoted to converting CO2 as a feedstock into various value-added chemicals, such as CH4 , lower methanol, light olefins, gasoline, and higher hydrocarbons, for numerous applications involving various catalytic reactions. Although several CO2 -conversion methods have been used, including electrochemical, photochemical, and biological approaches, the hydrogenation method allows the reaction to be tuned to produce the targeted compound without significantly altering infrastructure. This review discusses the numerous hydrogenation routes and their challenges, such as catalyst design, operation, and the combined art of structure-activity relationships for the various product formations.

Luminescence and Degeneration Mechanism of Perovskite Light-Emitting Diodes and Strategies for Improving Device Performance

Perovskite light-emitting diodes (PeLEDs) can be a promising technology for next-generation display and lighting applications due to their excellent optoelectronic properties. However, a systematical overview of luminescence and degradation mechanism of perovskite materials and PeLEDs is lacking. Therefore, it is crucial to fully understand these mechanisms and further improve device performances. In this work, the fundamental photophysical processes of perovskite materials, electroluminescence mechanism of PeLEDs including carrier kinetics and efficiency roll-off as well as device degradation mechanism are discussed in detail. In addition, the strategies to improve device performances are summarized, including optimization of photoluminescence quantum yield, charge injection and recombination, and light outcoupling efficiency. It is hoped that this work can provide guidance for future development of PeLEDs and ultimately realize industrial applications.