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Recently, perovskite solar cells (PSCs) and organic solar cells (OSCs) have emerged as solution-processable photovoltaic (PV) technologies with certified power conversion efficiencies (PCEs) surpassing 26% and 20%, respectively. However, challenges such as charge generation, separation, transport, collection, and recombination at the nanoscale still exist in fully controlling and understanding the performance-limiting factors in the photoactive layers of OSC and PSC devices. Although several efforts have been reported to address the above phenomena, the origin of the nanoscale defects and how they lead to performance losses have not yet been fully understood. This perspective provides an in-depth discussion of nanoscale spatial and time-resolved mapping for OSCs and PSCs to understand their roles in improving PV performance. A comprehensive multimodal technique to map the charge carrier photodynamics at the nanoscale, such as charge generation, separation, transport, collection, and recombination in OSCs and PSCs, is presented, which has the potential to evaluate the photodynamics related to local heterogeneities in the active layers of the corresponding devices. [ABSTRACT FROM AUTHOR]

All‐inorganic lead halide perovskite nanocrystals (NCs) have great optoelectronic properties with promising applications in light‐emitting diodes (LEDs), lasers, photodetectors, solar cells, and photocatalysis. However, the intrinsic toxicity of Pb and instability of the NCs impede their broad applications. Shell‐coating is an effective method for enhanced environmental stability while reducing toxicity by choosing non‐toxic shell materials such as metal oxides, polymers, silica, etc. However, multiple perovskite NCs can be encapsulated within the shell material and a uniform epitaxial‐type shell growth of well‐isolated NCs is still challenging. In this work, lead‐free vacancy‐ordered double perovskite Cs2SnX6 (X = Cl, Br, and I) shells are epitaxially grown on the surface of CsPbX3 NCs by a hot‐injection method. The effectiveness of the non‐toxic double perovskite shell protection is demonstrated by the enhanced environmental and phase stability against UV illumination and water. In addition, the photoluminescence quantum yields (PL QYs) increase for the CsPbCl3 and CsPbBr3 NCs after shelling because of the type I band alignment of the core/shell materials, while enhanced charge transport properties obtained from CsPbI3/Cs2SnI6 core/shell NCs are due to the efficient charge separation in the type II core/shell band alignment. [ABSTRACT FROM AUTHOR]

To meet the growing demand for energy storage technologies, it is crucial to develop next-generation energy storage and conversion devices with superior energy density, safety, low cost, and green sustainability. Li–air batteries (LABs) can catalyze the special redox reaction of light weight metal–oxygen (O2) couples, with superb theoretical energy density, low cost, and environmental friendliness, making them suitable for large-scale electricity storage technologies. However, an in-depth understanding of the root causes of poor battery performance and a well-defined electrochemical mechanism based on structural or material properties are still lacking. Hence, we discuss the main obstacles to the sluggish kinetics of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) at the cathode in LABs in this review. Exploration of a special redox reaction based on the design of the catalyst material is extremely instructive for battery development. Various design/manufacturing methods for nanoscale bifunctional electrocatalysts are introduced to offer general design principles. Electrocatalysts involve alloys, transition metal oxides (manganese-based, cobalt-based), other transition metal compounds (carbides/nitrides/sulfides), and carbon materials. The effects of different crystal structure designs on the bifunctional electrocatalytic mechanism of the OER/ORR are investigated at the nanoscale to guide performance improvement strategies. In addition, the root causes of poor battery performance caused by other components are discussed, as well as their possible future breakthroughs. Finally, the prospects of LABs should be highly focused on an integrated mechanism–structure–property strategy to guide catalyst synthesis and further integration with practical parameters for device development. [ABSTRACT FROM AUTHOR]

Over the past several years, kesterite Cu2ZnSnS4 (CZTS) absorber has been investigated comprehensively; however, the performance is still hampered by a large open-circuit voltage deficit associated with CZTS bulk defects and interface recombination. To overcome this trend, we report a facile approach to passivate both defect prone areas, i.e., bulk of CZTS and CZTS interface with a TiO2 buffer layer, simultaneously. The existence of oxygen ambient during TiO2 deposition has modulated the electrical properties of CZTS grain boundaries (GBs) not only inside the bulk but also at the surface of CZTS. The passivation of surface GBs is favorable for CZTS/TiO2 heterojunction electronic properties, whereas passivated bulk GBs improve the carrier transport inside the CZTS absorber. To directly probe the photovoltage generation at the CZTS/TiO2 heterojunction, Kelvin probe force microscopy is conducted in surface and junction modes. The acquired photovoltage map exhibits higher values at the GBs, which reveals an increment in downward band bending after oxygen diffusion inside the bulk of CZTS. In point of fact, the enhanced diffusion of oxygen accounts for the suppression of carrier recombination and reduction in dark current. Finally, current–voltage and capacitance–voltage measurements performed on the CZTS/TiO2 heterojunction further validate our outcomes. Our findings provide critical insight into the engineering of CZTS GBs to control electronic properties of CZTS and CZTS/TiO2 heterojunctions. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have made great strides in recent years, operating inside the theoretical Scholkely–Quisser efficiency limit with a certified power conversion efficiency (PCE) of 26.1%. However, lead toxicity from Pb‐based PSCs can harm the environment. As a result, the search for nontoxic and environmentally friendly substances to replace Pb in perovskites is the need of the hour. Tin has emerged as the most viable choice to replace Pb, due to its favorable electronic properties and smaller bandgaps of Sn‐based perovskites between 1.1 and 1.4 eV, strong charge carrier mobility, and high theoretical efficiency of 32%. Sn vacancies and point defects, on the other hand, are easily produced in Sn perovskites, leading to nonradiative recombination. Furthermore, interfacial flaws and traps impede further performance improvement. In this research, to produce high‐quality Pb‐free perovskites for high‐performance PSCs, a Lewis‐base thioacetamide (TAA) is added to the simple FASnI3 perovskite solution. FASnI3 and TAA additive‐based films effectively control perovskite film crystallinity and grain size via Lewis acid–base reaction. The champion FASnI3 + TAA‐based PSC achieves a maximum PCE of 10.67% while paving a facile way for other compositional perovskite analogues to be integrated into highly efficient and operationally stable PSCs. [ABSTRACT FROM AUTHOR]

The visual and instantaneous detection of trace levels of toxic lead ions (Pb2+) in water is still challenging. In this study, a perovskite precursor-based fluorescent sensor for visual and instantaneous detection of toxic Pb2+ in aqueous media has been demonstrated. A solution of Formamidinium Iodide (CH5IN2) salt showed excellent fluorescence quenching ability upon the addition of Pb2+ due to the formation of perovskite. Interestingly, this sensor requires three seconds for visual and instantaneous detection of Pb2+ in the range of 1 μM to 1 mM, which is the fastest response compared to the literature reports to the best of our knowledge. Furthermore, this sensor showed a linear fluorescent response with various concentrations of Pb2+ in the range of 100 nM to 1 mM. The sensor also showed a low detection limit of 100 nM for Pb2+, which is lower than the safety limit of Pb2+ in drinking water. In addition, the sensor showed excellent selectivity against a variety of interfering heavy metal ions including Hg2+, Cr3+, Zn2+, Cd2+, Ag+, etc. The excellent performance of the sensor could be attributed to the high electrostatic potential energy of the formamidinium cation (FA+), which was calculated using Density Functional Theory (DFT), that makes FA+ highly interactive toward Pb2+. Furthermore, the sensor demonstrated excellent feasibility for the detection of Pb2+ in real water samples, which confirms its potential for testing Pb2+ in environmental samples. [ABSTRACT FROM AUTHOR]

The photocurrent output of the C6H4NH2CuBr2I/TiO2 heterojunction photoelectrode in an aqueous solution is super stable even after 30 000 s. However, the photocurrent is extremely weak. Intensity-modulated photocurrent spectroscopy revealed that the electron transfer in the C6H4NH2CuBr2I/TiO2 photoelectrode without bias is not sufficiently fast to compete with the charge recombination process due to the short diffusion length (∼23 nm), resulting in a low photocurrent. The charge separation and charge transfer efficiency in the bulk of C6H4NH2CuBr2I could be significantly improved under a small reverse electric field (Er), resulting in an enhanced photocurrent. [ABSTRACT FROM AUTHOR]

All‐inorganic perovskite solar cells (PSCs) are most promising in yielding stabilized power conversion efficiencies (PCE) as compared to their hybrid organic–inorganic counterparts. However, all‐inorganic PSCs have suffered from low efficiency due to significant charge carrier recombination within perovskite active layer (PAL) bulk and at the carrier selective interfaces (CSI). Boosting the PCE through the remedy to both issues seems to be the only Achilles‐Heal on their way to commercialization. Here, a synergistic approach of liquid‐exfoliated molybdenum disulfide (MoS2) at the PAL (CsPbIBr2)/hole transport layer (NiO) interface to enhance the perovskite grain growth and stabilize the hole transport layer (HTL)/PAL interface against the carrier recombination within the PAL bulk and at the interface is reported. The in‐plane coupling between MoS2 crystal lattice and CsPbIBr2 is strongly revealed through transmission electron microscopy (TEM) results, which favored the van der Waals epitaxial growth of CsPbIBr2 PAL toward the larger crystalline grain sizes, preferential growth along (110), i.e., normal to MoS2, and low trap‐density. Therefore, the PCE of organic‐free CsPbIBr2 PSC is increased to as high as 10.98% under 1‐sun illumination, which is 48% higher than the pristine device (7.38%), which concludes that this strategy can be integrated to other analogous perovskite compositions. [ABSTRACT FROM AUTHOR]

Although the power conversion efficiency of Pb‐based perovskite solar cells (PSCs) has increased rapidly from 3.8% to 25.2%, the concerns about the toxicity of Pb greatly hinders its large‐scale application in the future. Therefore, many efforts have been made to develop environmentally benign Pb‐free perovskites, and there is a growing consensus that Sn‐based perovskites are by far the most promising alternative due to their ideal electric and optical properties. Among Sn‐based perovskites, CsSnI3 perovskite shows great promise for developing high‐efficiency Sn‐based PSCs due to its high thermal stability, ideal bandgap range, and low exciton binding energy. On the basis of the device engineering, an efficiency up to 10.1% has been reported for CsSnI3 PSCs. Nevertheless, considering the theoretical efficiency of CsSnI3 PSCs to be over 30%, there is still much room for improvement in the efficiency. Herein, the properties of CsSnI3 perovskite are summarized and the origins of stumbling the efficiency improvement of CsSnI3 PSCs are provided. The device engineering toward more stable and efficient CsSnI3 PSCs is discussed in detail. Finally, the remaining challenges and future perspectives in the field of CsSnI3 PSCs are also shown to help further the development of highly efficient CsSnI3 PSCs. [ABSTRACT FROM AUTHOR]