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Owing to the exceptional photovoltaic and optoelectronic properties of metal halide perovskites, they have sparked an intensive interest in the research community. CsPbBr₃ perovskite nanocrystals (NCs) have come into sight due to their versatile properties that can be achieved through structural modification. While the prior research on perovskite nanocrystals has focused mainly on tuning optical and electronic properties, the understanding of their electronic-ionic kinetics still remains a significant research gap. In this work, we explore how the size of CsPbBr₃ NCs impacts their electronic-ionic properties by using electrochemical impedance spectroscopy (EIS). We systematically tune NC size and investigate the resulting dielectric properties, conductivity, and capacitance. Notably, larger NCs exhibit anomalous behavior similar to that of perovskite polycrystalline thin films in the range of 0.4–0.6 V, indicating strong electronic-ionic coupling. Conversely, smaller NCs display weak electronic-ionic coupling due to ion localization. Additionally, this study sheds light on the electronic-ionic behavior of NCs approaching quantum confinement with a size reduction, suggesting opportunities for defect engineering. Ultimately, this work will pave the way for developing advanced electronic devices utilizing perovskite nanocrystals.

AgBiS2 nanocrystals have been shown to be a promising material for solar cell applications due to their high absorption coefficient, solution-processability and stability. However, detailed and systematic insight into how different surface passivation agents affect the overall material properties and corresponding device performance is still limited. Herein, a study about AgBiS2 nanocrystals treated with five different halide-based compounds - TBAI, TMAI, TBABr, TMABr and TMACl - is presented, with the nanocrystals themselves being synthesised via a newly adapted route under atmospheric conditions. For the differently passivated samples, variation in the ligand uptake, as well as shifts in the position of the valence and conduction bands could be observed. Incorporating these ligand-treated thin films into solar cell devices allowed for further investigation of their overall performance as well as into their respective charge carrier dynamics. Markedly longer charge carrier lifetimes were observed for the bromide- and chloride-passivated samples through transient photovoltage and photocurrent measurements as well as impedance spectroscopy. The effect of the surface modification on the charge carrier transport behaviour, on the other hand, was found to be less pronounced. Overall, this work demonstrates the importance of better understanding how different ligands affect nanocrystal properties, showcasing how it influences a wide variety of parameters controlling final device performance.

Recently, carbazole-based self-assembled monolayers (SAMs) have been utilized as hole transport layers (HTLs) in perovskite solar cells. However, their application in Sn or mixed Sn/Pb perovskite solar cells has been hindered by the poor wettability of the perovskite precursor solution on the carbazole surface. Here a self-assembled bilayer (SAB) comprising a covalent monolayer (Br-2PACz) and a noncovalent wetting layer (4CzNH3I) as the HTL in a Cs0.25FA0.75Sn0.5Pb0.5I3 perovskite solar cell is proposed. It is demonstrated that the wetting layer completely solves the problem due to the higher polarity of the surface and, furthermore, the ammonium groups help in the passivation of trap states at the buried SAB/perovskite interface. The introduction of the SAB enhances the device reproducibility with an average efficiency of 18.98 ± 0.28% (19.45% for the best device), compared to 11.54 ± 9.36% (19.34% for the best device) for the SAM-only devices. Furthermore, the improved perovskite processability on the SAB helps to increase the reproducibility of larger size device, where, a 12.5% efficiency for a 0.8 cm2 active area device compared to 0.68% for the best SAM-based solar cell is demonstrated. Finally, the device's operational stability is also improved to 358 hours (T80%), compared to 220 hours for the SAM-based solar cell.

Mixed tin/lead (Sn/Pb) perovskites have the potential to achieve higher performances in single junction solar cells compared to Pb-based compounds. The best Sn/Pb based devices are fabricated in a p-i-n structure, and PEDOT:PSS is frequently utilized as the hole transport layer, even if there are many doubts on a possible detrimental role of this conductive polymer. Here, we propose the use of [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz) and [2-(3, 6-dibromo-9H-carbazol-9-yl) ethyl] phosphonic acid (Br-2PACz) as substitutes for PEDOT:PSS. By using Cs(0.25)FA(0.75)Sn(0.5)Pb(0.5)I(3) as the active layer, we obtained record efficiencies as high as 19.51% on Br-2PACz, while 18.44% and 16.33% efficiencies were obtained using 2PACz and PEDOT:PSS, respectively. In addition, the implemented monolayers enhance both the shelf lifetime of the device as well as the operational stability. Finally, the Br-2PACz-based devices maintained 80% of their initial efficiency under continuous illumination for 230 h, and after being stored in a N-2 atmosphere for 4224 h (176 days).

Bromide-based perovskites have large bandgaps, making them attractive for tandem solar cells developed to overcome the Shockley–Queisser limit. A perovskite solar cell architecture employs transporting layers to improve charge extraction and transport. Due to the wide variety of materials and preparation methods, it is critical to devise fast screening methods to rank transporting layers. Herein, we evaluate perovskite fluorescence quenching followed by time- and energy-resolved photoluminescence (TER-PL) and analyse the intensity dependence as a potential method to qualify charge-transporting layers rapidly. The capability of the technique was evaluated with TiO₂/FAPbBr₃ and SnO₂/FAPbBr₃, the most commonly used electron transporting layers, which were prepared using standard protocols to make best-performing devices. The results revealed that TiO₂ is the most effective quencher due to the higher density of states in the conduction band, consistent with Marcus-Gerischer's theory. However, record-performance devices use SnO₂ as the electron transport layer. This shows that the relationship between photoluminescence quenching and device performance is not bidirectional. Therefore, additional measurements like conductivity are also needed to provide reliable feedback for device performance.

To remediate water bodies contaminated with organic micropollutants, recyclable and visible-light-driven coupled photocatalysis-peroxymonosulfate (PMS) activation systems were established by synthesizing magnetic-carbon-nanotubes (CNFe) modified TiO2-x/g-C3N4/CNFe (TCNCNFe) S-scheme heterojunction with oxygen vacancies (O-v) by a simple hydrothermal-calcination approach. The introduction of O-v and CNFe enhances the visible-light-harvesting efficiency and the internal electric field across the heterojunction accompanying favorable energy band bending could effectively migrate the photoexcited electrons along the S-scheme mechanism, thus highly suppressing in situ recombination and improving charge separation. Therefore the TCNCNFe-(30-500)/PMS/Vis system achieved 95.4% removal efficiency of atrazine after 30 min irradiation, meanwhile exhibited excellent recyclability without metal ion leaching due to the unique pod-like nanostructure of CNFe. Moreover, the impacts of certain various reaction variables on pollutant removal were explored to evaluate the practical application potential. Interestingly, the biotoxicity of the treated reaction filtrate was significantly alleviated compared to that of ATZ solution. Furthermore, the exploration of photocatalytic reaction mechanism revealed that the dominant reactive oxidizing species contributed in the following order: h(+) > (OH)-O-center dot > O-center dot(2)- > (SO4-)-S-center dot, and the feasible photodegradation pathway of atrazine was presented based on the determined in-termediates. Hence, this research work holds great promise in ecological environment protection using sustainable solar energy.

Despite considerable research efforts on photoelectrochemical water splitting over the past decades, practical application faces challenges by the absence of efficient, stable, and scalable photoelectrodes. Herein, we report a metal-halide perovskite-based photoanode for photoelectrochemical water oxidation. With a planar structure using mesoporous carbon as a hole-conducting layer, the precious metal-free FAPbBr3 photovoltaic device achieves 9.2% solar-to-electrical power conversion efficiency and 1.4 V open-circuit voltage. The photovoltaic architecture successfully applies to build a monolithic photoanode with the FAPbBr(3) absorber, carbon/graphite conductive protection layers, and NiFe catalyst layers for water oxidation. The photoanode delivers ultralow onset potential below 0 V versus the reversible hydrogen electrode and high applied bias photon-to-current efficiency of 8.5%. Stable operation exceeding 100 h under solar illumination by applying ultraviolet-filter protection. The photothermal investigation verifies the performance boost in perovskite photoanode by photothermal effect. This study is significant in guiding the development of photovoltaic material-based photoelectrodes for solar fuel applications.

High band gap FAPbBr(3) perovskite solar cellshave attractedtremendous interest in recent years due to the high open circuit voltageand good stability. Commonly a two-step method is used to preparethe FAPbBr(3) perovskite film. Here a mixed solvent approachfor the second step is introduced. Formamidinium bromide (FABr) in2-propanol and methanol mixture was applied in the second step, whichresulted in favorable properties such as suitable solubility, high-qualitycrystallization, large grain size, improved charge extraction properties,and suppressed non-radiative recombination processes, and furtherenhance the power conversion efficiency (PCE) from 4.06 to 7.87%.As previously reported, methylammonium chloride (MACl) can help toimprove the morphology and crystallinity of perovskite. To furtherprove the versatility of such a mixed solvent strategy and enhancethe photovoltage performance, a small amount of MACl was added tothe FABr solution with mixed solvents, and a high PCE of 9.23% wasachieved under ambient conditions.

Lead bromide perovskites have a larger band gap and are significantly more stable than their iodine counterparts, offering the perspective for higher voltage, tandem photovoltaics exceeding the Shockley-Queisser limit, and shorter time to deployment of photovoltaics. However, their efficiencies still need to be rivaling the iodine ones. Herein, the photophysics of FAPbBr(3) and the ones behind electron transfer from FAPbBr(3) to SnO2, one of the most effective electron transporting materials (ETMs), are reported. Time- and energy-resolved photoluminescence studies revealed the existence of two emitting states in the perovskite, which were assigned to bounded excitons and free carriers. SnO2 extracted electrons from excitons and free carriers, with a selectivity related to the SnO2 surface treatment. This new insight helps explain SnO2's unique qualities as an ETM to produce photovoltaics with reduced voltage losses. Furthermore, this study illustrates the importance of performing time- and energy-resolved photoluminescence to capture the intricacies of the photophysical process.

Renewable energy sources, such as wind and solar power, are increasingly important today to reduce emissions from fossil-based energy sources. However, the electricity from wind and solar power varies over time and depends on weather conditions and the time of the day. Therefore, to include a large fraction of electricity from these energy sources in the electricity grid, large-scale and low-cost energy storage is needed. Herein, it is investigated how a combination of quantum dot based photovoltaic cells and perovskite-based photovoltaic cells can be used to increase the energy conversion efficiency and increase the working range of energy storage devices based on conversion between heat, light, and electricity. The results show that these new types of photovoltaic materials have very promising properties for efficient utilization in energy storage devices, which have the potential for large-scale and low-cost energy storage.