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Organic–inorganic hybrid halide perovskites have emerged as the most promising optoelectronic materials for next‐generation solution‐processed devices, primarily attributed to their distinctive properties such as cost‐effectiveness, facile fabrication process, high light absorption coefficient, tunable bandgap, and relatively high charge carrier mobility. Nevertheless, the presence of Pb elements is inevitable in most high‐performance perovskite optoelectronic devices, posing environmental pollution concerns and impeding their commercialization. In this study, two novel non‐toxic bismuth‐ and antimony‐based perovskite materials with environmentally conscious approaches are developed. Their structures and optoelectronic properties have been systematically characterized. Subsequently, photoconductive‐ and photodiode‐type photodetectors are designed and fabricated. Notably, the photodiode configuration exhibits exceptionally low dark current and noise, superior detection sensitivity, fast response speed, and good device stability. Owing to these superior performance metrics, the devices demonstrate great potential for real applications. Furthermore, this study furnishes a theoretical framework and design perspectives for the solution‐processed semiconductor materials. [ABSTRACT FROM AUTHOR]

Highlights A unique approach is proposed: constructing a polymer fiber rigid network with high glass transition temperature. Frozen bulk heterojunction morphology impeded deterioration of exciton quenching, charge transport, and charge extraction properties during thermal aging. The strategy is universal and can be further optimized for enhanced thermal stability and improved mechanical resilience.

Metal halide perovskites are promising light absorbers for multijunction photovoltaic applications because of their remarkable bandgap tunability, achieved through compositional mixing on the halide site. However, poor energy‐level alignment at the interface between wide‐bandgap mixed‐halide perovskites and charge‐extraction layers still causes significant losses in solar‐cell performance. Here, the origin of such losses is investigated, focusing on the energy‐level misalignment between the valence band maximum and the highest occupied molecular orbital (HOMO) for a commonly employed combination, FA0.83Cs0.17Pb(I1‐xBrx)3 with bromide content x ranging from 0 to 1, and poly[bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine] (PTAA). A combination of time‐resolved photoluminescence spectroscopy and numerical modeling of charge‐carrier dynamics reveals that open‐circuit voltage (VOC) losses associated with a rising energy‐level misalignment derive from increasing accumulation of holes in the HOMO of PTAA, which then subsequently recombine non‐radiatively across the interface via interfacial defects. Simulations assuming an ideal choice of hole‐transport material to pair with FA0.83Cs0.17Pb(I1‐xBrx)3 show that such VOC losses originating from energy‐level misalignment can be reduced by up to 70 mV. These findings highlight the urgent need for tailored charge‐extraction materials exhibiting improved energy‐level alignment with wide‐bandgap mixed‐halide perovskites to enable solar cells with improved power conversion efficiencies. [ABSTRACT FROM AUTHOR]

Semiconductor nanowires have inspired plenty of novel nanotechnology device concepts in photonics, electronics, and sensing, owing to their unique functionalities and integrability in heterogeneous platforms. Lattice‐mismatched core/shell heterostructures, in particular, open new avenues for strain engineering and material properties modification. A notable case is the widely tunable tensile strain in the core of GaAs/InxAl1‐xAs core/shell nanowires, which can be used to tailor the GaAs bandgap for applications across near‐infrared, like optical fiber telecommunication, imaging, photovoltaics, etc. As it is shown here, though, the bandgap narrowing under high tensile strain in the GaAs core is accompanied by fast non‐radiative recombination, which is undesirable for any device application. The limiting role of the lattice‐mismatched core/shell interface is revealed, and a novel core/dual‐shell heterostructure that employs an intermediate AlyGa1‐yAs shell (spacer) is proposed. This spacer decouples the GaAs/AlyGa1‐yAs interface, which confines electrons and holes into GaAs, from the lattice‐mismatched AlyGa1‐yAs/InxAl1‐xAs one, whereas the strain in GaAs is unaffected. Choosing the optimal spacer thickness, the photoluminescence yield increases significantly, with longer emission decay lifetimes and slower carrier cooling rates. Besides unlocking the potential of GaAs for photonic applications across near‐infrared, the proposed heterostructure concept can also be adopted for other material systems. [ABSTRACT FROM AUTHOR]

Blue gallium nitride (GaN) light‐emitting diodes (LEDs), combined with red/green fluorescent converters, have broad potential for display applications. Metal halide perovskites now show excellent luminescence properties and may be suitable as light converters. Here a simple solution‐processed method is reported to prepare a methylammonium lead bromide (MAPbBr3) nanoporous GaN composite. Fast (within 2 ps) energy transfer is demonstrated from photoexcited nanoporous GaN to encapsulate MAPbBr3 nanocrystals, as observed by transient absorption spectroscopy. The spatial confinement of the perovskite within the nanoporous GaN is shown to increase the perovskite radiative recombination rate. These results offer guidelines for developing high‐performance perovskite/nanoporous GaN optoelectronics. [ABSTRACT FROM AUTHOR]

The photoelectrochemical reduction of nitrate to ammonia (PEC NO3RR) has emerged as a promising pathway for facilitating the natural nitrogen cycle. The PEC NO3RR can lower the reduction potential needed for ammonia synthesis through photogenerated voltage, showcasing the significant potential for merging abundant solar energy with sustainable nitrogen fixation. However, it is influenced by the selective photocathodes with poor carrier kinetics, low catalytic selectivity, and ammonia yields. There are few reports on suitable photoelectrodes owning efficient charge transport on PEC NO3RR at low overpotentials. Herein, we rationally constructed the CuSn alloy co‐catalysts on the antimony sulfides with a highly selective PEC ammonia and an ultra‐low onset potential (0.62 VRHE). CuSn/TiO2/Sb2S3 photoelectrodes achieved an ammonia faradic efficiency of 97.82 % at a low applied potential of 0.4 VRHE, and an ammonia yield of 16.96 μmol h−1 cm−2 at 0 VRHE under one sun illumination. Dynamics experiments and theoretical calculations have demonstrated that CuSn/TiO2/Sb2S3 has an enhanced charge separation and transfer efficiency, facilitating photogenerated electrons to participate in PEC NO3RR quickly. Meanwhile, moderate NO2* adsorption on this photocathode optimizes the catalytic activity and increases the NH4+ yield. This work opens an avenue for designing sulfide‐based photocathodes for the efficient route of solar‐to‐ammonia conversion. [ABSTRACT FROM AUTHOR]

Grain boundaries (GBs) in perovskite polycrystalline films are the most sensitive place for the formation of the defect states and the accumulation of impurities. Thus, abundant works have been carried out to explore their properties and then try to solve the induced problems. Currently, two important issues remain. First, the role of GBs in charge carrier dynamics is unclear due to their component complexity/defect tolerance nature and the insufficiency in testing accuracy. Some works conclude that GBs are benign, while others consider GBs as carrier recombination centers. Things for sure are the deterioration in ion transport and perovskite decomposition. Second, to solve the known hazards of GBs, a lot of additives have been added to anchoring ions and passivate defects. But in most of those works, GBs and perovskite surfaces are treated in the same manner ignoring the fact that GB is essentially a homogeneous junction in a narrow and slender space, while surface is a heterogeneous junction with a stratified structure. In this review, we focus on works insight into GBs and additives for them. Additionally, we also discuss the prospects of the maturity of GB exploration toward upscaling the manufacture of perovskite photovoltaic and related optoelectronic devices. [ABSTRACT FROM AUTHOR]

Highlights : A unique approach is proposed: constructing a polymer fiber rigid network with high glass transition temperature. Frozen bulk heterojunction morphology impeded deterioration of exciton quenching, charge transport, and charge extraction properties during thermal aging. The strategy is universal and can be further optimized for enhanced thermal stability and improved mechanical resilience. Organic photovoltaics (OPVs) need to overcome limitations such as insufficient thermal stability to be commercialized. The reported approaches to improve stability either rely on the development of new materials or on tailoring the donor/acceptor morphology, however, exhibiting limited applicability. Therefore, it is timely to develop an easy method to enhance thermal stability without having to develop new donor/acceptor materials or donor–acceptor compatibilizers, or by introducing another third component. Herein, a unique approach is presented, based on constructing a polymer fiber rigid network with a high glass transition temperature (Tg) to impede the movement of acceptor and donor molecules, to immobilize the active layer morphology, and thereby to improve thermal stability. A high-Tg one-dimensional aramid nanofiber (ANF) is utilized for network construction. Inverted OPVs with ANF network yield superior thermal stability compared to the ANF-free counterpart. The ANF network-incorporated active layer demonstrates significantly more stable morphology than the ANF-free counterpart, thereby leaving fundamental processes such as charge separation, transport, and collection, determining the device efficiency, largely unaltered. This strategy is also successfully applied to other photovoltaic systems. The strategy of incorporating a polymer fiber rigid network with high Tg offers a distinct perspective addressing the challenge of thermal instability with simplicity and universality. [ABSTRACT FROM AUTHOR]

A power conversion efficiency (PCE) exceeding 25% is achievable using perovskite solar cells (PSCs), with compositional engineering as the most effective strategy for high‐efficiency PSCs. However, the understanding of structural properties, charge‐carrier dynamics, and photoelectric properties, crucial for solar cell performance, still remains insufficient to establish a correlation with device performance for improving the PCE and stability of PSCs. This study uncovers the crucial links between structural disorder, charge‐carrier dynamics, and photoelectric properties of mixed‐perovskite (FAPbI3)1‐x(MAPbBr3)x thin films by investigating device performance for different mol%. Structural and morphological analyses reveal that the mixed perovskite‐thin‐film disorder exhibits composition dependence in the form of a checkmark trend, with a minimum near 0.8 mol%. Time‐resolved transient absorption spectroscopy demonstrates that charge‐carrier dynamics and optoelectronic properties exhibit a corresponding dependence on disorder. As the disorder of the perovskite thin film decreases, the trap density decreases, charge‐carrier loss decreases during the thermalization process, and the carrier lifetime is prolonged. Optical pump‐THz probe measurements show 20% effective mobility and a diffusion length of 34%. The device performance shows composition dependence and superior PCE is achieved at 0.8 mol%. This study highlights the significance of charge‐carrier dynamics in optimizing mixed perovskite composition for enhanced PCE and stability of PSCs. [ABSTRACT FROM AUTHOR]

The main obstacles to promoting the commercialization of perovskite solar cells (PSCs) include their record power conversion efficiency (PCE), which still remains below the Shockley–Queisser limit, and poor long‐term stability, attributable to crystallographic defects in perovskite films and open‐circuit voltage (Voc) loss in devices. In this study, potassium (4‐tert‐butoxycarbonylpiperazin‐1‐yl) methyl trifluoroborate (PTFBK) was employed as a multifunctional additive to target and modulate bulk perovskite defects and carrier dynamics of PSCs. Apart from simultaneously passivating anionic and cationic defects, PTFBK could also optimize the energy‐level alignment of devices and weaken the interaction between carriers and longitudinal optical phonons, resulting in a carrier lifetime of greater than 3 μs. Furthermore, it inhibited non‐radiative recombination and improved the crystallization capacity in the target perovskite film. Hence, the target rigid and flexible p‐i‐n PSCs yielded champion PCEs of 24.99 % and 23.48 %, respectively. More importantly, due to hydrogen bonding between formamidinium and fluorine, the target devices exhibited remarkable thermal, humidity, and operational tracking at maximum power point stabilities. The reduced Young's modulus and residual stress in the perovskite layer also provided excellent bending stability for flexible target devices. [ABSTRACT FROM AUTHOR]

State‐of‐the‐art triple cation, mixed halide perovskites are extensively studied in perovskite solar cells, showing very promising performance and stability. However, an in‐depth fundamental understanding of how the phase behavior in Cs0.05FA0.85MA0.10Pb(I0.97Br0.03)3 (CsMAFA) affects the optoelectronic properties is still lacking. The refined unit cell parameters a and c in combination with the thermal expansion coefficients derived from X‐ray diffraction patterns reveal that CsMAFA undergoes an α–β phase transition at ≈280 K and another transition to the γ‐phase at ≈180 K. From the analyses of the electrodeless microwave photoconductivity measurements it is shown that shallow traps only in the γ‐phase negatively affect the charge carrier dynamics. Most importantly, CsMAFA exhibits the lowest amount of microstrain in the β‐phase at around 240 K, corresponding to the lowest amount of trap density, which translates into the longest charge carrier diffusion length for electrons and holes. Below 200 K a considerable increase in deep trap states is found most likely related to the temperature‐induced compressive microstrain leading to a huge imbalance in charge carrier diffusion lengths between electrons and holes. This work provides valuable insight into how temperature‐dependent changes in structure affect the charge carrier dynamics in FA‐rich perovskites. [ABSTRACT FROM AUTHOR]

Understanding electron and ion dynamics is an important task for improving modern energy materials, such as photovoltaic perovskites. These materials usually have delicate nano‐ and microstructures that influence the device parameters. To resolve detailed structure–function relationships on the relevant micro‐ and nanometer length scales, the current macroscopic and microscopic measurement techniques are often not sufficient. Here, nanoscale surface photovoltage spectroscopy (nano‐SPV) and nanoscale ideality factor mapping (nano‐IFM) via time‐resolved Kelvin probe force microscopy are introduced. These methods can map nanoscale variations in charge carrier recombination, ion migration, and defects. To show the potential of nano‐SPV and nano‐IFM, these methods are applied to perovskite samples with different morphologies. The results clearly show an improved uniformity of the SPV and SPV decay distribution within the perovskite films upon passivation and increasing the grain size. Nevertheless, nano‐SPV and nano‐IFM can still detect local variations in the defect density on these optimized samples, guiding the way for further optimization. [ABSTRACT FROM AUTHOR]

Recently, multijunction tandem solar cells (TSCs) have presented high power conversion efficiency and revealed their immense potential in photovoltaic evolution. It is demonstrated that multiple light absorbers with various bandgap energies overcome the Shockley–Queisser limit of single‐junction solar cells by absorbing the wide‐range wavelength photons. Here, the main key challenges are reviewed, especially the charge carrier dynamics in perovskite‐based 2‐terminal (2‐T) TSCs in terms of current matching, and how to manage these issues from a vantage point of characterization. To do this, the effect of recombination layers, optical and fabrication hurdles, and the impact of wide bandgap perovskite solar cells are discussed extensively. Afterward, this review focuses on various optoelectronics, spectroscopic, and theoretical (optical simulation) characterizations to figure out those issues, especially current‐matching issues faced by the photovoltaic society. This review comprehensively provides deep insights into the relationship between the current‐matching problems and the photovoltaic performance of TSCs through a variety of perspectives. Consequently, it is believed that this review is essential to address the main problems of 2‐T TSCs, and the suggestions to elucidate the charge carrier dynamics and its characterization may pave the way to overcome such obstacles to further improve the development of 2‐T TSCs in relation to the current‐matching problems. [ABSTRACT FROM AUTHOR]

Ultrafast charge carrier dynamics of green‐light emitting InP/ZnSe/ZnS core–shell quantum dots (QDs) with three different ZnSe thickness of 2.0 nm (gQD‐20), 2.4 nm (gQD‐24), or 3.3 nm (gQD‐33) are interrogated by femtosecond transient absorption (TA) and femtosecond stimulated Raman spectroscopy (FSRS). Auger‐type cooling of hot electron into the band‐edge level of InP is clearly manifested in the TA spectra, giving its time constant of ≈222, 300, or 349 fs for gQD‐20, gQD‐24, or gQD‐33, respectively, indicating that the state‐filling to the 1S(e) of InP is significantly slowed down with the increase of the mid shell thickness. The global analysis of the whole TA spectra turns out to be extremely useful to explain the dynamic behavior of the heterogeneous ensemble of single and/or bi‐ (or multi‐) excitons in the presence of the Stark‐shift. The hole‐relaxation dynamics into the band‐edge 1S (h) of the core InP is revealed in the bleaching dynamics of the FSR bands corresponding to the phonon mode of InP or ZnSe, giving the estimated lifetime of 1.0–1.4 ps for gQD‐20. The hole‐relaxation dynamics by the phonon emission seem to be little sensitive to the ZnSe shell thickness. [ABSTRACT FROM AUTHOR]

Organic solar cell (OSC) development continues to demonstrate impressive device efficiency improvements. However, the materials synthetic simplicity essential to industrialization remains seriously lacking attention, imparting inferior performance records in low‐cost devices. Hence, low bandgap and completely non‐fused electron acceptors (CNFEAs) having simple molecular structures are investigated herein. In contrast to typically explored fused‐ring acceptors with smaller backbone conformational variations, minimizing the interface recombination sites through a greater extent of localized domains is identified as more critical in CNFEAs, leading to remarkable fill factors (FFs) approaching 75%, among the highest currently realized for low‐cost systems. However, this comes with diminishing charge generation efficiency. The general ternary blend optimization strategy modifying the morphology of host components is limited in preserving such remarkably high FFs. To suppress the trade‐off while keeping notable FFs, a new perspective of constructing functionally bridged components based on optical, electronic, and thermodynamic properties is introduced here. Specifically, charge generation is unrestrained from the host acceptor localized domains through the introduction of a "bridge" component while also taking advantage of the configuration to channel polarons toward the efficient transport moieties of the host components. Accordingly, this work incubates understanding‐guided optimizations toward the advancement of more practical devices. [ABSTRACT FROM AUTHOR]

Abstract Ultrafast charge carrier dynamics of green‐light emitting InP/ZnSe/ZnS core–shell quantum dots (QDs) with three different ZnSe thickness of 2.0 nm (gQD‐20), 2.4 nm (gQD‐24), or 3.3 nm (gQD‐33) are interrogated by femtosecond transient absorption (TA) and femtosecond stimulated Raman spectroscopy (FSRS). Auger‐type cooling of hot electron into the band‐edge level of InP is clearly manifested in the TA spectra, giving its time constant of ≈222, 300, or 349 fs for gQD‐20, gQD‐24, or gQD‐33, respectively, indicating that the state‐filling to the 1S(e) of InP is significantly slowed down with the increase of the mid shell thickness. The global analysis of the whole TA spectra turns out to be extremely useful to explain the dynamic behavior of the heterogeneous ensemble of single and/or bi‐ (or multi‐) excitons in the presence of the Stark‐shift. The hole‐relaxation dynamics into the band‐edge 1S (h) of the core InP is revealed in the bleaching dynamics of the FSR bands corresponding to the phonon mode of InP or ZnSe, giving the estimated lifetime of 1.0–1.4 ps for gQD‐20. The hole‐relaxation dynamics by the phonon emission seem to be little sensitive to the ZnSe shell thickness.

With near unity quantum efficiency and operational stability surpassing 250 days in outdoor conditions, aluminum‐doped SrTiO3 (Al:SrTiO3) with tailored cocatalysts is one of the promising photocatalysts for scalable solar H2 production. Nevertheless, mechanistic insights behind Al‐doping and Rh cocatalyst‐induced enhanced overall water splitting (OWS) efficiency are not well elucidated. Herein, detailed charge carrier dynamics from sub‐picosecond to milliseconds are unveiled for Al:SrTiO3 by transient (optical and microwave probe) spectroscopy measurements. The obtained transients are rationalized using a theoretical model considering bimolecular recombination, trapping and detrapping processes. Due to a decrease in an n‐type doping density, Al doping of SrTiO3 significantly prolongs bulk carrier lifetime from 50 ns to 12.5 µs (consistent with the previous report). The crucial electron extraction process by the Rh cocatalyst located on the surface from Al:SrTiO3 occurs well before the decay of charge carriers. In contrast, µs‐long electron extraction time observed in SrTiO3 is significantly slower than tens of ns bulk carrier lifetime, thus reducing the photocatalytic OWS reaction. Complementary analysis in conjunction with in situ charge carrier dynamics in water interface addresses the mechanistic insight into Al‐doping‐induced enhancement of OWS activity. Correlating material properties, carrier dynamics and photocatalytic activity is expected to help design next‐generation photocatalysts via dopant and/or defects engineering for efficient solar‐fuel production. [ABSTRACT FROM AUTHOR]

With power conversion efficiencies approaching 20%, organic solar cells can no longer be considered the ugly duckling of photovoltaics. Successes notwithstanding, there is still a need for further improvement of organic solar cells, both regarding energy and current management in these devices. At present, there are different and mutually exclusive interpretation schemes for the associated losses of energy and charge, hampering the rational design of next generations of organic solar cells. One critical factor that affects voltage, current, and fill factor losses is whether or not photogenerated charges are effectively near or far away from thermodynamic equilibrium. While it is commonly agreed that both the vibronic and (disordered) energetic structure of organic semiconductors affect the solar cell characteristics, the degree to which deviations from near‐equilibrium population of the associated energy level distributions matter for the photovoltaic performance is unclear: near‐equilibrium as well as kinetic descriptions have provided seemingly convincing descriptions of a wide range of experiments. Here, the most important concepts in relation to experimental results are reviewed, open questions are addressed and implications for device performance and improvement are highlighted. [ABSTRACT FROM AUTHOR]

In this study, we present a comprehensive investigation into the charge generation mechanism in bulk-heterojunction organic solar cells employing non-fullerene acceptors (NFAs) both with and without the presence of processing additives. While photovoltaic devices based on Y6 or BTP-eC9 have shown remarkable power conversion efficiencies, the underlying charge generation mechanism in polymer:NFA blends remains poorly understood. To shed light on this, we employ transient absorption (TA) spectroscopy to elucidate the charge transfer pathway within a blend of the donor polymer PM6 and NFAs. Interestingly, the charge carrier lifetimes of neat Y6 and BTP-eC9 are comparable, both reaching up to 20 ns. However, the PM6:BTP-eC9 blend exhibits substantially higher charge carrier generation and a longer carrier lifetime compared to PM6:Y6 blend films, leading to superior performance. By comparing TA data obtained from PM6:Y6 or PM6:BTP-eC9 blend films with and without processing additives, we observe significantly enhanced charge carrier generation and prolonged charge carrier lifetimes in the presence of these additives. These findings underscore the potential of manipulating excited species as a promising avenue for further enhancing the performance of organic solar cells. Moreover, this understanding contributes to the advancement of NFA-based systems and the optimization of charge transfer processes in polymer:NFA blends. [ABSTRACT FROM AUTHOR]

The quality of the perovskite absorption layer is critical for the high efficiency and long‐term stability of perovskite solar cells (PSCs). The inhomogeneity due to local lattice mismatch causes severe residual strain in low‐quality perovskite films, which greatly limits the availability of high‐performance PSCs. In this study, a multi‐active‐site potassium salt, pemirolast potassium (PP), is added to perovskite films to improve carrier dynamics and release residual stress. X‐ray photoelectron spectroscopy (XPS) and Fourier‐transform infrared spectroscopy (FTIR) measurements suggest that the proposed multifunctional additive bonds with uncoordinated Pb2+ through the carbonyl group/tetrazole N and passivated I atom defects. Moreover, the residual stress release is effective from the surface to the entire perovskite layer, and carrier extraction/transport is promoted in PP‐modified perovskite films. As a result, a champion power conversion efficiency (PCE) of 23.06% with an ultra‐high fill factor (FF) of 84.36% is achieved in the PP‐modified device, which ranks among the best in formamidinium‐cesium (FACs) PSCs. In addition, the PP‐modified device exhibits excellent thermal stability due to the inhibited phase separation. This work provides a reliable way to improve the efficiency and stability of PSCs by releasing residual stress in perovskite films through additive engineering. [ABSTRACT FROM AUTHOR]

Abstract With power conversion efficiencies approaching 20%, organic solar cells can no longer be considered the ugly duckling of photovoltaics. Successes notwithstanding, there is still a need for further improvement of organic solar cells, both regarding energy and current management in these devices. At present, there are different and mutually exclusive interpretation schemes for the associated losses of energy and charge, hampering the rational design of next generations of organic solar cells. One critical factor that affects voltage, current, and fill factor losses is whether or not photogenerated charges are effectively near or far away from thermodynamic equilibrium. While it is commonly agreed that both the vibronic and (disordered) energetic structure of organic semiconductors affect the solar cell characteristics, the degree to which deviations from near‐equilibrium population of the associated energy level distributions matter for the photovoltaic performance is unclear: near‐equilibrium as well as kinetic descriptions have provided seemingly convincing descriptions of a wide range of experiments. Here, the most important concepts in relation to experimental results are reviewed, open questions are addressed and implications for device performance and improvement are highlighted.

The use of colloidal nanocrystals as part of artificial photosynthetic systems has recently gained significant attention, owing to their strong light absorption and highly reproducible, tunable electronic and optical properties. The complete photocatalytic conversion of water to its components is yet to be achieved in a practically suitable and commercially viable manner. To complete this challenging task, we are required to fully understand the mechanistic aspects of the underlying light-driven processes involving not just single charge carriers but also multiple charge carriers in detail. This review focuses on recent progress in understanding charge carrier dynamics in semiconductor nanocrystals and the influence of various parameters such as dimension, composition, and cocatalysts. Transient absorption spectroscopic studies involving single and multiple charge carriers, and the challenges associated with the need for accumulation of multiple charge carriers to drive the targeted chemical reactions, are discussed. [ABSTRACT FROM AUTHOR]

Organo–inorganic halide perovskites continue to generate enormous interest for their potential use in various optoelectronic devices. Among the different fabrication methods, vacuum thermal deposition allows uniform films over large areas, providing good material quality without using organic solvents. However, the influence of the substrate on the properties of the material deposited by vacuum processing is a point that deserves further investigation. Herein, time‐dependent photoconductivity measurements are used to investigate the dynamics of charge carriers under illumination in planar films of CH3NH3PbI3. The samples are deposited by thermal sublimation on different substrates: PbI2, TaTm, C60, and glass. Experimentally, it is shown that the substrate has a profound effect on perovskite behavior and that photoconductivity is sensitive enough to probe these behaviors. Furthermore, a model based on Shockley–Read–Hall statistics is proposed, explaining the different photoconductivity responses by changing only the relative values of the different capture coefficients and the position of the Fermi level. It is argued that the substrate changes the stoichiometry of the evaporated material, affecting the transient photoconductivity response. [ABSTRACT FROM AUTHOR]

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.

In this study, we present a comprehensive investigation into the charge generation mechanism in bulk-heterojunction organic solar cells employing non-fullerene acceptors (NFAs) both with and without the presence of processing additives. While photovoltaic devices based on Y6 or BTP-eC9 have shown remarkable power conversion efficiencies, the underlying charge generation mechanism in polymer:NFA blends remains poorly understood. To shed light on this, we employ transient absorption (TA) spectroscopy to elucidate the charge transfer pathway within a blend of the donor polymer PM6 and NFAs. Interestingly, the charge carrier lifetimes of neat Y6 and BTP-eC9 are comparable, both reaching up to 20 ns. However, the PM6:BTP-eC9 blend exhibits substantially higher charge carrier generation and a longer carrier lifetime compared to PM6:Y6 blend films, leading to superior performance. By comparing TA data obtained from PM6:Y6 or PM6:BTP-eC9 blend films with and without processing additives, we observe significantly enhanced charge carrier generation and prolonged charge carrier lifetimes in the presence of these additives. These findings underscore the potential of manipulating excited species as a promising avenue for further enhancing the performance of organic solar cells. Moreover, this understanding contributes to the advancement of NFA-based systems and the optimization of charge transfer processes in polymer:NFA blends.

Investigation of the effects of Zr-doping in silver niobate (AgNbO3) had been carried out to improve the photocatalytic performance of AgNbO3. The X-ray diffraction patterns of the AgNbO3 and Zr-doped AgNbO3 showed that the materials are pure and have no overall change in phase upon Zr-doping. The Fourier transform infrared spectra showed an intense wide band due to bonding between Nb and O which is observed within the specified range of AgNbO3. Field emission scanning electron microscopy analysis showed that the particle size decreases with increasing Zr-doping. Tauc plots derived from the UV–Vis absorption spectra showed that Zr-doping has a limited effect on band gap narrowing. Furthermore, the photoluminescence data was indicative of lowered charge recombination rate in the Zr-doped AgNbO3 compared to AgNbO3. The photocatalytic performance of Zr-doped AgNbO3 was also studied for the degradation of RhB and MB dyes under visible light.

Recent advances in the growth of III-V semiconductor nanowires (NWs) hold great promise for nanoscale optoelectronic device applications. It is established that a small amount of nitrogen (N) incorporation in III-V semiconductor NWs can effectively red-shift their wavelength of operation and tailor their electronic properties for specific applications. However, understanding the impact of N incorporation on non-equilibrium charge carrier dynamics and transport in semiconducting NWs is critical in achieving efficient semiconducting NW devices. In this work, ultrafast optical pump-terahertz probe spectroscopy has been used to study non-equilibrium carrier dynamics and transport in Te-doped GaAsSb and dilute nitride GaAsSbN NWs, with the goal of correlating these results with electrical characterization of their equilibrium photo-response under bias and low-frequency noise characteristics. Nitrogen incorporation in GaAsSb NWs led to a significant increase in the carrier scattering rate, resulting in a severe reduction in carrier mobility. Carrier recombination lifetimes of 33 ± 1 picoseconds (ps) and 147 ± 3 ps in GaAsSbN and GaAsSb NWs, respectively, were measured. The reduction in the carrier lifetime and photoinduced optical conductivities are due to the presence of N-induced defects, leading to deterioration in the electrical and optical characteristics of dilute nitride NWs relative to the non-nitride NWs. Finally, we observed a very fast rise time of ∼2 ps for both NW materials, directly impacting their potential use as high-speed photodetectors. [ABSTRACT FROM AUTHOR]

Lead‐free double perovskite Cs2AgBiBr6 has gained increasing attention recently. However, the power conversion efficiency (PCE) of Cs2AgBiBr6 perovskite solar cells (PSCs) is still low compared with their lead‐based counterparts. Here, by using photoluminescence (PL), time‐resolved photoluminescence (TRPL), and ultrafast transient absorption (TA) measurements, the unbalance between the electron and hole in diffusion and transfer, which limits the performance of the Cs2AgBiBr6 PSCs, was further revealed. Considering this issue, a strategy of using the mesoporous TiO2 electron transport layer (ETL) to construct a bulk heterojunction in Cs2AgBiBr6 PSCs was proposed. Consequently, the PCE had improved by over 24% comparing with that only used compact TiO2 ETL. Moreover, based on mesoporous TiO2, the unencapsulated Cs2AgBiBr6 PSCs maintained 90% of their initial performance after approximately 1200 h of storage in a desiccator (humidity ~30%). This work gives further understanding of Cs2AgBiBr6 perovskite and demonstrates that a proper design of balancing the electron and hole diffusion can improve device performance. [ABSTRACT FROM AUTHOR]

Summary: A novel Bi2WO6/rGO/3D‐GCN composite with 2D/2D/3D heterojunction is synthesized by a simple microwave‐assisted method and used as a visible‐light‐responsive photocatalyst in the CO2 reduction. The chemical properties and morphology of prepared photocatalysts are identified by a variety of analytic tools and spectroscopies. As a result, the heterojuncted Bi2WO6/3D‐GCN exhibits superior CO2 reduction performance as compared to the pristine 3D‐GCN, which may be caused by the intimate contact between Bi2WO6 and 3D‐GCN. The harvest of visible‐light absorption, reduced charge transfer resistance and suppressed recombination of electron‐hole pairs are accountable for surpassing performance of Bi2WO6/3D‐GCN. Upon further incorporation of rGO into Bi2WO6/3D‐GCN heterojunction, the photocatalytic production of CO can be notably boosted by ca. 7.9‐fold higher than 3D‐GCN, suggesting the key contribution of rGO in facilitating the interfacial charge transfer kinetics and increasing CO2 uptake. This work exemplifies a time and energy‐saving method to prepare the unique 3D GCN with laminated hexagonal structure which can serve as a shuttle for Bi2WO6 heterojunction and rGO incorporation. This Bi2WO6/rGO/3D‐GCN photocatalyst could offer the potential applications in the natural solar conversions of CO2. [ABSTRACT FROM AUTHOR]

Organic-inorganic halide perovskite solar cells (PSCs) have attracted significant attention in photovoltaic research, owing to their superior optoelectronic properties and cost-effective manufacturing techniques. However, the unbalanced charge carrier diffusion length in perovskite materials leads to the recombination of photogenerated electrons and holes. The inefficient charge carrier collecting process severely affects the power conversion efficiency (PCE) of the PSCs. Herein, a solution-processed SnO 2 array electron transport layer with precisely tunable micro-nanostructures is fabricated via a bubble-template-assisted approach, serving as both electron transport layers and scaffolds for the perovskite layer. Due to the optimized electron transporting pathway and enlarged perovskite grain size, the PSCs achieve a PCE of 25.35% (25.07% certificated PCE)., (© 2024 Wiley‐VCH GmbH.)

Nanopatterned halide perovskites have emerged to improve the performance of optoelectronic devices by controlling the crystallographic and optical properties via morphological modification. However, the correlation between the photophysical property and morphology transformation in nanopatterned perovskite films remains elusive, which hinders the rational design of nanopatterned halide perovskites for optoelectronic devices. In this study, we employed nanoimprinting lithography on a perovskite film to exert a precise control over grain growth and manipulate electronic structures at the level of individual grains. Surface-selective fluorescence lifetime imaging microscopy (FLIM) analyzes the spatiotemporally disentangled geometrical variations in carrier recombination rate and band structure modulation according to different pattern morphologies. Consequently, the stereoscopic mechanism of confined grain growth was unveiled, highlighting the quantitative grain size-based parameters that are crucial for nanoscale material engineering. Notably, the pattern-induced reduction of effective charge mass enabled exclusive control over the subdiffusive carrier transport dynamics on perovskite surfaces, ultimately realizing the surface-selective perovskite photodetectors. The implications of this study are expected to provide valuable guidelines, inspiring innovative design protocols for advancing the next-generation optoelectronic technologies.

Perovskite solar cells (PSCs) are attracting widespread research and attention as highly promising candidates in the field of electronic photovoltaics owing to their exceptional power conversion efficiency (PCE). However, rigid or flexible PSCs still face challenges in preparing full-coverage and low-defect perovskite films, as well as achieving highly reproducible and highly stable devices. Herein, a multifunctional additive 2-aminoethyl hydrogen sulfate (AES) is designed to regulate the film crystallization and thereby form flat and pinhole-free perovskite films. It is found that the introduction of AES can effectively passivate defects, restrain charge carrier recombination, and then achieve a higher fill factor. As seen with grazing incidence wide-angle X-ray scattering (GIWAXS), this approach does not affect the crystal orientation distribution. It is observed that AES addition shows a universality across different perovskite components since the PCE is improved up to 20.7% for FA 0.97 MA 0.03 Pb(I 0.97 Br 0.03 ) 3 -AES, 22.85% for Cs 0.05 FA 0.95 PbI 3 -AES, 22.23% for FAPbI 2.7 Br 0.3 -AES, and 23.32% for FAPI-AES rigid devices. Remarkably, the non-encapsulated flexible Cs 0.05 (FA 0.85 MA 0.15 ) 0.95 Pb(I 0.85 Br 0.15 ) 3 device with AES additive delivers a PCE of 20.1% and maintains over 97% of its initial efficiency under ambient conditions (25 ± 5% relative humidity) over 2280 h of aging., (© 2024 The Authors. Small published by Wiley‐VCH GmbH.)

The use of colloidal nanocrystals as part of artificial photosynthetic systems has recently gained significant attention, owing to their strong light absorption and highly reproducible, tunable electronic and optical properties. The complete photocatalytic conversion of water to its components is yet to be achieved in a practically suitable and commercially viable manner. To complete this challenging task, we are required to fully understand the mechanistic aspects of the underlying light-driven processes involving not just single charge carriers but also multiple charge carriers in detail. This review focuses on recent progress in understanding charge carrier dynamics in semiconductor nanocrystals and the influence of various parameters such as dimension, composition, and cocatalysts. Transient absorption spectroscopic studies involving single and multiple charge carriers, and the challenges associated with the need for accumulation of multiple charge carriers to drive the targeted chemical reactions, are discussed.

Metal halide perovskites having high defect tolerance, high absorption characteristics, and high carrier mobility demonstrate great promise as potential light harvesters in photovoltaics and optoelectronics and have experienced an unprecedented development since their occurrence in 2009. Semiconductor quantum dots (QDs), on the other hand, have also been proved to be very flexible toward shape, dimension, bandgap, and optical properties for constructing optoelectronic devices. Of late, a strategic combination of both materials has demonstrated extraordinary promise in photovoltaic applications and optoelectronic devices. Combining QDs and perovskites has proved to be quite an effective strategy toward the formation of pinhole‐free and more stable perovskite crystals along with tunability of other properties. To boost this exciting research field, it is imperative to summarize the work done so far in recent years to provide an intriguing insight. This review is a critical account of the advanced strategy toward combining these two fascinating materials, including their different synthetic approaches regarding heteroepitaxial growth of perovskite crystals on QDs, carrier dynamics at the interface and potential application in the field of solar cells, light emitting diodes, and photodetectors. [ABSTRACT FROM AUTHOR]

Monoclinic α‐Ag2S is an intriguing member of transition metal sulfides with great potential for all‐inorganic flexible optoelectronics and thermoelectrics. Fabrication of large‐area, high‐quality α‐Ag2S thin films and understanding their charge transport properties are critical for device operations yet have remained largely unexplored. Here, a novel two‐step, the solution‐processed approach is reported to produce wafer‐sized, highly crystalline α‐Ag2S thin films. Ultrafast terahertz (THz) conductivity measurements reveal that photogenerated charge carriers undergo efficient band transport, with room‐temperature mobility of ≈150 cm2 V‐1 s‐1 and a diffusion length exceeding 500 nm. Furthermore, introducing poly(vinyl alcohol) (PVA) as the rigid component into the aqueous silver thiolate precursor enables the synthesis of free‐standing α‐Ag2S thin films with a mobility of ≈35 cm2 V‐1 s‐1, demonstrating their potential for flexible optoelectronics. This study provides a facile synthesis route for high‐quality, large‐area α‐Ag2S thin films with good charge transport properties, relevant for their integration into optoelectronics and wearable electronics. [ABSTRACT FROM AUTHOR]

Sb2Se3 has emerged as an important photoelectrochemical (PEC) and photovoltaic (PV) material due to its rapid rise in photoconversion efficiencies. However, Sb2Se3 has a complex defect chemistry, which reduces the maximum photovoltage. Thus, it is important to understand these defects and develop defect passivation strategies in Sb2Se3. A comprehensive investigation of the charge carrier dynamics of Sb2Se3 and the influence of sulfur treatment on its optoelectronic properties is performed using time‐resolved microwave conductivity (TRMC), photoluminescence (PL) spectroscopy, and low‐frequency Raman spectroscopy (LFR). The key finding in this work is that upon sulfur treatment of Sb2Se3, the carrier lifetime is increased by the passivation of deep defects in Sb2Se3 in both the surface region and the bulk, which is evidenced by increased charge carrier lifetime of TRMC decay dynamics, increased radiative recombination efficiency, decreased deep defect level emission (PL), and the emergence of new vibration modes by LFR. [ABSTRACT FROM AUTHOR]

[Display omitted] • Potassium precursor choice significantly affects g-C 3 N 4 ′s photocatalytic behavior. • K precursors differently increase density of localised states and light harvesting. • Choice of precursor, not amount of K, crucially impacts CB/VB potentials in g-C 3 N 4. • KCl precursor significantly enhanced surface ability of g-C 3 N 4 to form ·OH radicals. • TCSPC revealed higher average carrier lifetime in KCl-based g-C 3 N 4 compared to KOH. The previous studies on K-doped g-C 3 N 4 suggest a simple correlation between the increased potassium content and the improved photocatalytic activity due to a shift of the valence band potential to more positive values, leading to the direct oxidation of hydroxyl ions to hydroxyl radicals by holes. In this study, we investigated the influence of different potassium precursors on the properties and photocatalytic efficiency of K-modified g-C 3 N 4 materials in Rhodamine B degradation. Detailed characterization revealed that the choice of precursor significantly affects the structural and optoelectronic properties with complex correlations rather than superficial relationships between potassium content and photocatalytic activity. Notably, KCl-based samples, despite having a lower specific surface area, exhibited enhanced photocatalytic properties due to prolonged carrier lifetimes and improved charge transfer efficiency compared to KOH-based samples. Higher precursor concentrations resulted in more recombination centers, increasing Urbach energy and reducing photocatalytic activity. These findings underscore the importance of precise synthesis control, revealing that both K and Cl atoms act as charge transfer bridges, improving the material's photocatalytic properties beyond mere surface area enhancement. In addition, even smaller amounts of Cl atoms in g-C 3 N 4 showed much higher impact on the final position of conduction and valence band potentials than K atoms. [ABSTRACT FROM AUTHOR]

Charge transfer and subsequent separation into free carriers are key processes that govern the efficiencies of third generation solar cell technologies based on donor-acceptor heterojunctions. As these processes typically occur on picosecond to femtosecond timescales, it is necessary to employ ultrafast spectroscopic techniques to further our understanding of these processes in order to provide vital information that can aide in furthering material design. Within the framework of the National Centre of Competence in Research “Molecular Ultrafast Science and Technology” (NCCR MUST), we have developed and utilized a suite of different ultrafast spectroscopic techniques to study charge generation, separation and recombination in a variety of small molecule based organic solar cells and lead halide perovskites. Here, we provide an overview of the main techniques used in our laboratory and the recent results obtained using these spectroscopic techniques.

"Necessity is the mother of invention." The global imperative to transition from fossil fuels to renewable energy sources, driven by the pressing issue of climate change, highlights the significance of advancing solar energy technologies. While single junction solar cells have reached a peak efficiency of approximately 31 %, the pursuit of higher efficiency has led to the exploration of tandem solar cell architectures, including perovskite-silicon and all-perovskite configurations. However, the widespread use of lead in perovskite structures raises environmental and health concerns. In response to these challenges, this study proposes a novel approach by integrating a tin-based wide bandgap absorber layer with a silicon HIT solar cell (Heterojunction with Intrinsic Layer). The investigation consists of an extensive exploration of six different carrier transport layers (CTL) for the top perovskite layer, considering variations in thickness and defect density. A comprehensive analysis of charge carrier dynamics within the device is conducted to understand the role of defect density in influencing solar cell performance parameters. Simulation results show that the overall tandem device gives an encouraging PCE of 32.12 % in 2 T configuration due to its excellent high value of current density matching 17.63 mA/cm2 and open-circuit voltage of 2.19V. We sincerely hope that our work will open new avenues in the field of Solar Photovoltaics paving the way for future innovations. [Display omitted] Significance of the work. • Detailed study and understanding of the role of lead free perovskite absorber layers with Industrial solar cell. • Utilizing a tin-based absorber layer with a bandgap of 1.61eV, in tandem configuration with a silicon HIT solar cell (Heterojunction with intrinsic layer) having a bandgap of 1.12eV. • The overall tandem device gives an encouraging PCE of 32.12 % in 2 T configuration due to its excellent high value of current density matching. • The experimental validation of simulation study with previously published data is critical. [ABSTRACT FROM AUTHOR]

Water motion-induced energy generation has been studied intensively due to its potential for sustainable green energy harvesting. Although significant research efforts have been dedicated to attaining effective energy generation, the role of the water-permeable interlayer has been largely neglected. Herein, a composite material comprising reduced graphene oxide and cellulose nanofiber (rGO:CNF) is proposed. By embedding water-permeable interlayers, substantial power enhancement and long-term sustainability are observed with the potential to operate as long as sufficient water is supplied. The optimized unit device generates a voltage of 0.72 V and a current of 1.2 µA. Moreover, LED lights as a buoy warning system are prepared by connecting 12 devices in series. The generated power and energy reach 120 μW/cm2 and 133 mWh/cm2 for 53 continuous days, respectively. This finding offers insights behind realizing a high power density and exceptionally durable system through the ionovoltaic effect for expanding the water motion-induced energy harvesting field. [Display omitted] • Embedding water-permeable interlayers create stable pathways for water interaction. • Enhanced solid–liquid interaction improves power conversion efficiency. • Continuous flow of water contact line generates a highly sustainable electricity. • Ionovoltaic energy generation mechanism is elucidated by an energy band alignment. • A buoy light is activated for over 50 days with energy density up to 133 mWh/cm2. [ABSTRACT FROM AUTHOR]

Recent advances in photovoltaic devices demonstrate a potential candidature of the lead halide perovskite solar cells (PSCs) to fulfill the all-electric future of the world. Further improvements in efficiency and stability require minimization of non-radiative recombination arising due to the tr ap states created by the vacancies and defects. The device’s performance is mostly determined by the perovskite absorber material, which has single-cation, mixed-cation, and/or mixed-halide composition-dependent optoelectronic capabilities. Herein, we present an insight on the state of the art of PSCs, including types of defects, their effects, and remedies of the same. Various design strategies administered to grow highly crystalline perovskite films with low defects at interfaces are described in detail. The inclusion of a few nm thin interlayer between perovskite and charge transport layer (CTL) is an effective way to passivate the defect at the interface. Furthermore, additive engineering is emerging as an excellent strategy to grow the defect-free perovskite by simply adding a polymer, ionic liquids, organic/inorganic salts in precursor solution without precipitating after film formation. The mitigation of charge recombination could be achieved by efficient charge extraction through proper energy alignment of CTLs and absorbers. Notably, we emphasize the interface, additive, and gradient band alignment engineering and resulting improvement in the photocurrent density, photovoltage, power conversion efficiency, and long-term stability. The present review gives complete information about PSCs, starting from the selection of the materials to PSC fabrication, charge carrier dynamics, defects, effects, and remedies. We hope that this summarised information will give a basic understanding of designing new passivation strategies for advancing PSC’s present state of the art. [ABSTRACT FROM AUTHOR]

Constructing favorable heterointerface to facilitate photogenerated carrier transport is an effective way to improve the photocatalytic activities of semiconductor catalysts. However, the fabrication of atomic-level interface remains a challenge due to the difficulties in constructing intimate interface contact. Herein, a unique atom-to-atom TiO 2 /ZrTiO 4 heterointerface with the potential formation of Ti–O–Ti(Zr) bonds between TiO 2 and ZrTiO 4 was constructed through the in-situ formation of the two components using a one-step sol-gel method. The resulting photocatalyst exhibited superior photocatalytic activity and high stability, i.e., about 97% of Rhodamine B was degraded after visible light irradiation for 90 min for three consecutive photodegradation cycles. By further analyses such as refined X-ray diffractometer (XRD), X-ray photoelectron spectrometer (XPS), Raman microscope (Raman), photoluminescence (PL), and photoelectrochemical spectra (TP and EIS), it revealed that the atom-to-atom heterointerface of TiO 2 /ZrTiO 4 with stronger interaction forces would greatly accelerate the charge separation as well as provide generous defect sites, boosting the number of photogenerated carriers available at reaction sites, thus contribute to the improvement of photocatalytic performance. The present work demonstrates a new approach of in-situ construction for interface engineering TiO 2 based catalyst, providing design guidelines for heterointerface photocatalytic structures. [ABSTRACT FROM AUTHOR]