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Comprehensive Summary Key Scientists With the continuous development of photovoltaic materials, organic solar cells (OSCs) have made remarkable advancements, surpassing a power conversion efficiency (PCE) of 20%. However, the PCEs of OSCs remain lower than that of inorganic solar cells due to significant energy losses, mainly stemming from the relatively large non‐radiative recombination losses (usually be expressed as ∆E3), resulting in low open‐circuit voltages. This can be achieved by reducing non‐radiative recombination, and hereby increasing the electroluminescence quantum efficiency (EQEEL) of the photo‐active layer. This review analyzes the significance of luminescence efficiency in achieving high‐performance OSCs by examining the reciprocal relationship between ∆E3 and EQEEL. High‐efficiency organic solar cells can also be used as effective organic light‐emitting diodes (OLEDs). The discussion provides insights into the influencing factors of EQEEL and the mechanisms for adjusting various parameters, which include enhancements in photoluminescence quantum yield and the proportion of radiative excitons. The objective is to offer insights into the crucial role of luminescence performance in OSC development, guiding researchers toward developing novel photovoltaic materials or optimization strategies to enhance the luminescence performance of the active layer in OSCs, fostering the simultaneous advancement of OSCs and OLEDs. [ABSTRACT FROM AUTHOR]

Interface in perovskite solar cells (PSCs) is of vital importance because it dominates deep‐level defects and non‐radiative recombination, thus impacting both efficiency and stability further. Herein, a symmetrical acceptor–donor–acceptor (A–D–A) conjugated molecule with the core architecture of terthieno[3,2‐b hiophene and 2‐(3‐oxo‐2,3‐dihydro‐1 H‐inden‐1‐ylidene)malononitrile, named 6TIC, as a versatile buffer layer, is adopted to enhance photovoltaic performance and stability simultaneously. It is found that the conjugated molecule filling at grain boundaries and surface can not only chemically anchor with perovskite components to substantially eliminate interfacial defects and suppress detestable non‐radiative recombination, but also effectively improve the energy level alignment and facilitate charge transfer efficiency at the interface, resulting in an excellent power conversion efficiency of 24.81% with an admirable fill factor of 84.5%. Furthermore, benefiting from the unexceptionable surface protection effect of the hydrophobic buffer layer, greatly improved operational stability is delivered, with retaining 90% of initial efficiency for 960 h aging in a relative humidity of 60 ± 5% air and 1450 h aging under continuous 85 °C heating stress. This strategy may provide a new avenue for advancing high‐efficiency and stable PSCs. [ABSTRACT FROM AUTHOR]

To get maximum efficiency, potential in perovskite solar cells (PSCs) has made it hot research area now a days. Power conversion efficiency of PSCs is increasing by every passing day. Moreover, performance of perovskite absorber layer is important for high efficiency andlong term stability of PSCs. In this work, 2‐4 (Methyl sulphonyl) Phenyl) Ethylamine small molecules with functional groups are added inperovskite and enlarged grains are observed in the result. These effects show improvement in the performance of perovskite. Consequently, density of imperfections with additive in PSCs is alleviated and champion efficiency 24.16% has been achieved. Within corporation of additive with polar functional group crystallinity of absorber film is increased, that is confirmed by X‐ray diffraction and Uv‐Vis results. PL result show absorption is increased with addition ofadditive due to mitigation of nonradiative charge recombination. It is confirmed by GIWAX that charge transportation is increased since output peakintensity for (100) plane is larger than that of input. Overall, efficiencyis increased from 22% for control and exceeding 24% and stability enhanced with incorporation of small molecules. [ABSTRACT FROM AUTHOR]

Incorporating noble‐metal plasmonic nanoparticles (NPs) enhances the optoelectronic properties of perovskite solar cells (PSCs) but at a higher cost. In this work, the overlooked potential of refractory plasmonic materials is highlighted as a cost‐effective alternative additive in PSC research. This investigation aims to stimulate interest in this area by showcasing the theoretical and practical impacts of TiN plasmonic NPs when integrated into PSCs. TiN plasmonic NPs present a cost‐effective yet underexplored option. This study explores the impact of TiN NPs on PSCs through theoretical and experimental approaches. Finite‐difference time‐domain (FDTD) optical simulations and empirical data indicate that TiN NPs increase absorption and reduce reflectance in PSCs, driven by surface plasmon resonance and the significant growth of perovskite grains from 450 to 1400 nm. These NPs also regulate the perovskite crystallization rate by adsorbing DMF/DMSO, fostering larger grain formation. Improved band alignment and decreased trap states enhance charge transport and diminish non‐radiative recombination losses. As a result, PSC efficiency with optimal TiN NP concentration increased from 19.07% to 21.37%. Additionally, TiN‐enhanced PSCs display better stability, retaining 98.1% of their original PCE after 31 days under ambient conditions. [ABSTRACT FROM AUTHOR]

Perovskite solar cells have become a leading contender in next‐generation photovoltaic technologies due to their high efficiency and low‐cost potential. Managing the deep defects present effectively in the crystal lattice and at the interfaces is essential for enhancing the performance and longevity of perovskite solar cells. Here, perovskite's crystallization modulation and interfacial defect passivation are achieved by developing a guanidinium iodide (GAI)‐based surface passivation strategy. The integration of GAI passivates the grain boundaries, leading to a perovskite thin film with a smoother and more uniform grain distribution, facilitating charge carrier transport. Notably, the ammonium group, unsaturated nitrogen atoms, and iodide ions in GAI can collectively repair the surface defects of perovskite through various pathways, effectively suppressing non‐radiative recombination, thereby enhancing the photovoltaic performance of the device. Ultimately, the champion device treated with GAI achieves a power conversion efficiency (PCE) of 23.02% and demonstrates similar ambient stability under unencapsulated conditions. These findings underscore the effectiveness of GAI passivation as a strategy to balance the improvement of the performance and stability of perovskite solar cells. [ABSTRACT FROM AUTHOR]

Achieving high efficiencies in halide perovskite solar cells with thicknesses >1 µm is necessary for developing perovskite‐Si tandem cells based on small pyramidal structures. To achieve this goal, not only is the perovskite layer quality to be optimized but also the properties of the charge‐transport layers must be tuned to reduce charge‐collection losses. The transport layers provide a non‐ohmic resistance that modulates the Fermi‐level splitting inside the perovskite absorber. The finite conductivity of the transport layers can lead to losses in the fill factor (FF) and short‐circuit current, even at infinite charge‐carrier mobility in the absorber layer. These losses notably scale with the absorber layer thickness, which implies that higher‐conductivity transport layers are required for thicker perovskite absorbers. One strategy to improve charge collection and thereby FFs in thick inverted perovskite solar cells is to use bilayers of hole‐transport layers. In this study, the combination of poly[bis(4‐phenyl) (2,4,6‐trimethylphenyl)amine] with self‐assembled monolayers provides the best photovoltaic performance in single‐junction devices. [ABSTRACT FROM AUTHOR]

Antimony selenosulfide (Sb2(S,Se)3) solar cells bear great potential for sustainable photovoltaic technology, attributed to their excellent semiconductor properties. Despite the encouraging breakthroughs, the efficiency of Sb2(S,Se)3 solar cells still leaves much room for improvement due to the large open‐circuit voltage (VOC) deficit (the radiative VOC limit minus the high VOC). Herein, ammonium sulfide ((NH4)2S) solution is utilized to treat Sb2(S,Se)3 films to tailor their surface properties. The disappearance of the hole defect (H1) and the decrease of the defect concentration of hole defect (H2) confirm that non‐radiative recombination is suppressed greatly. Photovoltage decay lifetime is greatly increases from 67.9 to 297.9 µs. The upshifted valence band maximum optimizes the energy level alignment between the p–n heterojunction, enhancing the carrier transport. Remarkably, this treatment yields a record lowest VOC deficit of 0.49 V by now, and the best device with 10.41% efficiency, ca. 25% improvement over the control device (8.35%). This study provides valuable insight into reducing the VOC deficit in solar cells and related photoelectronic devices by minimizing non‐radiative recombination, and also presents a great potential strategy to achieve the lowest VOC deficit. [ABSTRACT FROM AUTHOR]

Perovskite solar cells have demonstrated low non‐radiative voltage losses and open‐circuit voltages (VOCs) that often match the internal voltage in the perovskite layer, i.e. the quasi‐Femi level splitting (QFLS). However, in many cases, the VOC differs remarkably from the internal voltage, for example in devices without perfect energy alignment. In terms of recombination losses, this loss often outweighs all non‐radiative recombination losses observed in photoluminescence quantum efficiency measurements by many orders of magnitude. As such, understanding this phenomenon is of great importance for further perovskite solar cell development and tackling stability issues. The classical theory developed for Si solar cells explains the QFLS‐VOC mismatch by considering the partial resistances/conductivities for majority and minority carriers. Here, the authors demonstrate that this generic theory applies to a variety of physical mechanisms that give rise to such a mismatch. Additionally, it is found that mobile ions can contribute to a QFLS‐VOC mismatch in realistic perovskite cells, and it is demonstrated that this can explain various key observations about light soaking and aging‐induced VOC losses. The findings in this paper shine a light on well‐debated topics in the community, identify a new degradation loss, and highlight important design principles to maximize the VOC for improved perovskite solar cells. [ABSTRACT FROM AUTHOR]

Due to their excellent photoelectric conversion efficiency and low preparation cost, perovskite solar cells (PSCs) have attracted much attention from researchers and developed rapidly in the past decade. However, the stability and efficiency of perovskite photovoltaic devices still need to be improved for their practical applications. It is mainly because the perovskite thin films are inevitably defective to some extent (such as points defects and extrinsic defects), leading to the occurrence of non‐radiative recombination (NRR) inside the device and at the interface, which is closely related to the stability and efficiency of perovskite materials. Therefore, exploring reliable passivation strategies is essential to overcome the adverse effects of NRR losses of such point defects. Here, this article summarizes the perovskite solar cells, including the crystal structure and calculations of electronic properties of perovskites, composition, and principles of operation of perovskite solar cells, and more importantly, different passivation strategies, including Lewis acid‐base passivation, anionic and cationic passivation, polymer passivation, and alkyl halogen ammonium passivation for the defects involved in perovskite materials. The passivation effects of these strategies and their regulation mechanisms of point defects involving perovskite materials are also presented. We also discuss the intrinsic relationship between crystal defects and device stability and look forward to feasible defect passivation strategy options for future research. [ABSTRACT FROM AUTHOR]

Selecting suitable charge transport layers and suppressing non‐radiative recombination at interfaces with the absorber layer is vital for maximizing the efficiency of halide perovskite solar cells. In this study, high‐quality perovskite thin films and devices are fabricated with different fullerene‐based electron transport layers and different self‐assembled monolayers as hole transport layers. Then, a comparative study of a significant variety of different electrical, optical, and photoemission‐based characterization techniques is performed to quantify the properties of the solar cells, individual layers, and, importantly, the interfaces between them. In addition, the limitations and problems of the different measurements, the insights gained by combining different methods, and the different strategies for extracting information from the experimental raw data, are highlighted. [ABSTRACT FROM AUTHOR]

The low cost and scalability advantages of printable mesoscopic perovskite solar cells (p‐MPSCs) are impaired by the issue of limited power conversion efficiency (PCE). Herein, the PCE of p‐MPSCs is improved by introducing the polymer additive polyacrylonitrile (PAN) into the formamidinium (FA)‐based perovskite for crystallization and defect modulation. PAN forms hydrogen bond and coordination bond with halide perovskite through its C≡N group. Such interactions improve the crystallization and filling of FA‐based perovskite in the mesoscopic scaffold and bring a long carrier lifetime by passivating defects. The synergy improves the PCE of p‐MPSCs from 16.80% to 18.33%. Meanwhile, the hydrophobic nature of PAN enhances the device's resistance against moisture. This work demonstrates that the polymer additive is a promising choice for breaking the PCE limit of p‐MPSCs. [ABSTRACT FROM AUTHOR]

Interface engineering strategy plays an essential role in improving the photovoltaic performance of perovskite solar cells (PSCs). In this study, nickel oxide (NiOx) films are fabricated by the low‐temperature combustion method and modified by poly[bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine] (PTAA) solution with a low concentration. Then, NiOx and NiOx/PTAA films are used as hole transport layers to fabricate low‐dimensional perovskite (4FPEA)2(MA0.9FA0.1)3Pb4I13 (n=4) (4FPEA: 4‐fluorophenylethylammonium, MA: methylammonium, FA: formamidinum). The experimental results show that the energy level alignment has been optimized by introducing a PTAA layer, which is beneficial to improving the hole extraction efficiency. Therefore, the low‐dimensional PSC exhibit the high open‐circuit voltage (1.21 V) by suppressing the non‐radiative recombination. Compared with the PSC based on NiOx film, the power conversion efficiency of the PSC based on NiOx/PTAA film is improved from 6.13 % to 12.25 %. Meanwhile, the PSC based on NiOx/PTAA film remains at 88 % of the initial efficiency after being stored in a nitrogen glove box for 900 h. Our work offers a promising route for applying NiOx film in low‐dimensional PSCs. [ABSTRACT FROM AUTHOR]

Successful manipulation of halide perovskite surfaces is typically achieved via the interactions between modulators and perovskites. Herein, it is demonstrated that a strong‐interaction surface modulator is beneficial to reduce interfacial recombination losses in inverted (p‐i‐n) perovskite solar cells (IPSCs). Two organic ammonium salts are investigated, consisting of 4‐hydroxyphenethylammonium iodide and 2‐thiopheneethylammonium iodide (2‐TEAI). Without thermal annealing, these two modulators can recover the photoluminescence quantum yield of the neat perovskite film in contact with fullerene electron transport layer (ETL). Compared to the hydroxyl‐functionalized phenethylammonium moiety, the thienylammonium facilitates the formation of a quasi‐2D structure onto the perovskite. Density functional theory and quasi‐Fermi level splitting calculations reveal that the 2‐TEAI has a stronger interaction with the perovskite surface, contributing to more suppressed non‐radiative recombination at the perovskite/ETL interface and improved open‐circuit voltage (VOC) of the fabricated IPSCs. As a result, the VOC increases from 1.11 to 1.20 V (based on a perovskite bandgap of 1.63 eV), yielding a power conversion efficiency (PCE) from ≈20% to 21.9% (stabilized PCE of 21.3%, the highest reported PCEs for IPSCs employing poly[N,N′′‐bis(4‐butylphenyl)‐N,N′′‐bis(phenyl)benzidine] as the hole transport layer, alongside the enhanced operational and shelf‐life stability for unencapsulated devices. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have attracted wide attention due to their capacity to achieve high‐power conversion efficiencies. However, the high trap‐assisted recombination taking place in the active layer leads to performance loss in PSCs. In particular, the excessive recombination at the interface between the perovskite active layer and the carrier selective contacts can be especially problematic. Therefore, the identification of the dominant recombination pathways in a given PSC architecture is of significant importance for the mitigation of losses and enhancement of device performance. Here, we introduce an approach for identifying the dominant recombination pathways in PSCs by applying illumination‐side‐dependent impedance spectroscopy (ISD‐IS) measurements on the devices with a semi‐transparent top electrode. We validate this technique using coupled ionic‐electronic numerical simulations and apply it experimentally on a standard PSC structure. Overall, this approach could be of significant importance for pinpointing the performance bottlenecks in PSC devices under operationally relevant conditions and providing a more detailed picture of the losses in a complete PSC device by examining its behaviors under illumination from both sides at different operation conditions, which could allow for a more targeted optimization strategy of PSCs to improve their performance. [ABSTRACT FROM AUTHOR]

To enhance the fluorescence efficiency of semiconductor nanocrystal quantum dots (QDs), strategies via enhancing photo‐absorption and eliminating non‐radiative relaxation have been proposed. In this study, we demonstrate that fluorescence efficiency of molybdenum disulfide quantum dots (MoS2 QDs) can be enhanced by single‐atom metal (Au, Ag, Pt, Cu) modification. Four‐fold enhancement of the fluorescence emission of MoS2 QDs is observed with single‐atom Au modification. The underlying mechanism is ascribed to the passivation of non‐radiative surface states owing to the new defect energy level of Au in the forbidden band that can trap excess electrons in n‐type MoS2, increasing the recombination probability of conduction band electrons with valence band holes of MoS2. Our results open an avenue for enhancing the fluorescence efficiency of QDs via the modification of atomically dispersed metals, and extend their scopes and potentials in a fundamental way for economic efficiency and stability of single‐atom metals. [ABSTRACT FROM AUTHOR]

A recombination and exciton loss mechanism is reported in organic solar cells involving energy transfer between charge transfer (CT) excitons and polarons, impacting photocurrent generation, particularly in the near‐infrared where polaronic transitions typically reside. This process sets a low‐energy cut‐off in the external quantum efficiency spectrum of an excitonic donor/acceptor interface, determined by the low‐energy polaron absorption peak and the CT state reorganization energy. Furthermore, this process explains the deviation from unity and bias dependence of the CT state's internal quantum efficiency at low photon energies. This process is demonstrated in a variety of systems and it is hypothesized that CT state to polaron energy transfer recombination may be responsible for a share of nonradiative recombination in all organic photovoltaics and can explain numerous experimentally observed device trends regarding photocurrent generation and energy losses. Overall, this work enhances the understanding of photophysical processes in organic materials and allows the design of systems that can avoid this recombination pathway. [ABSTRACT FROM AUTHOR]

Impressive short‐circuit current density and fill factor have been achieved simultaneously in single‐junction organic solar cells (OSCs) with the emergence of high‐performance non‐fullerene acceptors. However, the power conversion efficiencies (PCEs) of OSCs still lag behind those of inorganic and perovskite solar cells, mainly due to the modest open‐circuit voltage (VOC) imposed by relatively large energy loss (Eloss). Generally, Eloss in solar cells can be divided into three parts. Among them, ΔE1 is inevitable for all photovoltaic cells and depends on the optical bandgap of solar cells, while radiative recombination energy loss, ΔE2, in OSCs can approach the negligible value via finely matching donor with acceptor material in the blend. The relatively large non‐radiative recombination energy loss, ΔE3, becomes the main barrier to further reduce Eloss and thus enhance PCE in non‐fullerene acceptor‐based OSCs. In this review, the recent studies and achievements about ΔE3 in non‐fullerene acceptor‐based OSCs have been summarized from the aspects of material design, morphology manipulation, ternary strategy, mechanism, and theoretical study. It is hoped that this review helps to get a deep understanding and boost the advance of ΔE3 study in OSCs. [ABSTRACT FROM AUTHOR]

Interfacial engineering is the key to high‐performance perovskite solar cells (PSCs). While a wide range of fullerene interlayers are investigated for Pb‐based counterparts with a bandgap of >1.5 eV, the role of fullerene interlayers is barely investigated in Sn‐Pb mixed narrow‐bandgap (NBG) PSCs. In this work, two novel solution‐processed fullerene derivatives are investigated, namely indene‐C60‐propionic acid butyl ester and indene‐C60‐propionic acid hexyl ester (IPH), as the interlayers in NBG PSCs. It is found that the devices with IPH‐interlayer show the highest performance with a remarkable short‐circuit current density of 30.7 mA cm−2 and a low deficit in open‐circuit voltage. The reduction in voltage deficit down to 0.43 V is attributed to reduced non‐radiative recombination that the authors attribute to two aspects: 1) a higher conduction band offset of ≈0.2 eV (>0 eV) that hampers charge‐carrier‐back‐transfer recombination; 2) a decrease in trap density at the perovskite/interlayer/C60 interfaces that results in reduced trap‐assisted recombination. In addition, incorporating the IPH interlayer enhances charge extraction within the devices that results in considerable enhancement in short‐circuit current density. Using a NBG device with an IPH interlayer, a respectable power conversion efficiency of 24.8% is demonstrated in a four‐terminal all‐perovskite tandem solar cell. [ABSTRACT FROM AUTHOR]

Wide‐bandgap perovskites have attracted substantial attention due to their important role in serving as a top absorber in tandem solar cells (TSCs). However, wide‐bandgap perovskite solar cells (PVSCs) typically suffer from severe non‐radiative recombination loss and therefore exhibit high open‐circuit voltage (VOC) deficits. To address these issues, a 2D octyl‐diammonium lead iodide interlayer is adopted onto the hole‐transporting layer to induce the formation of an ultrathin quasi‐2D perovskite that is close to the hole‐selective interface. This approach not only accelerates hole transfer and retards hole accumulation but also reduces the trap density in the perovskite layer on top, thereby efficiently suppresses non‐radiative recombination pathways. Consequently, the champion wide‐bandgap device (≈1.66 eV) exhibits a power conversion efficiency (PCE) of 21.05% with a VOC of 1.23 V, where the VOC deficit of 0.43 V is among the lowest values for inverted wide‐bandgap PVSCs. Moreover, by stacking a semi‐transparent perovskite top cell on a 1.1 eV Cu2ZnSn(S,Se)4 (CZTSSe) bottom cell, a 22.27% PCE was achieved on a perovskite/CZTSSe four‐terminal tandem solar cell, paving the way for all‐solution‐processed, low‐cost, and efficient TSCs with mitigated energy loss in the wide‐bandgap top cells. [ABSTRACT FROM AUTHOR]

Efficient mixed metal lead‐tin halide perovskites are essential for the development of all‐perovskite tandem solar cells, however they are currently limited by significant short‐circuit current losses despite their near optimal bandgap (≈1.25 eV). Herein, the origin of these losses is investigated, using a combination of voltage dependent photoluminescence (PL) timeseries and various charge extraction measurements. It is demonstrated that the Pb/Sn‐perovskite devices suffer from a reduction in the charge extraction efficiency within the first few seconds of operation, which leads to a loss in current and lower maximum power output. In addition, the emitted PL from the device rises on the exact same timescales due to the accumulation of electronic charges in the active layer. Using transient charge extraction measurements, it is shown that these observations cannot be explained by doping‐induced electronic charges but by the movement of mobile ions toward the perovskite/transport layer interfaces, which inhibits charge extraction due to band flattening. Finally, these findings are generalized to lead‐based perovskites, showing that the loss mechanism is universal. This elucidates the negative role mobile ions play in perovskite solar cells and paves a path toward understanding and mitigating a key loss mechanism. [ABSTRACT FROM AUTHOR]

The electron donor/acceptor (D/A) heterojunction is the core for photocharge generation and recombination in organic photovoltaics (OPVs). Developing practical methods for the D/A heterojunction modification remains challenging and is rarely discussed in OPV research. Herein, the roles of molecular doping at the D/A heterojunction in the charge‐transfer exciton dissociation and detailed energy loss are investigated, and new insights are gained into the functions of doping on the OPV performance. Heterojunction doping simultaneously enhances all three OPV parameters, especially the short‐circuit current (Jsc). It is shown that the Jsc improvement is due to the combined effects of strengthened electric field and reduced activation energy, which is regulated via an entropy‐related mechanism. The performance enhancement is further demonstrated in homojunction devices showing the great potential of interfacial doping to overcome the intrinsic limitation between high Jsc and open‐circuit voltage (Voc) in OPVs. [ABSTRACT FROM AUTHOR]

Post‐treatment is of great importance to form nanoscale phase‐separated morphology for all‐small‐molecule organic solar cells (ASM‐OSCs), while the reasons for the difference between thermal annealing (TA) and solvent annealing (SVA) remain unclear. In this work, the influences of TA and SVA (with three common solvents of THF, CS2, and CF) are systematically investigated based on BT‐2F:N3 through characterization of photovoltaic performance, molecular stacking, charge transfer, etc. The results indicate that: i) solvents with good solubility induce stronger molecular interaction than that of TA treatment, and thus endowing molecules with better mobility to migrate for crystallization and phase separation, which leads to better J‐aggregation and molecular interconnection. ii) Donor‐selectively dissolved CS2 is better for optimizing the donor domain for its suitable domain size, improved molecular interaction and interconnection, and reduced trap states. iii) CS2 imposes a small impact on N3 acceptors and thus alleviates the increment of non‐radiative recombination. As a result, CS2 SVA with unique multifunctions enables a PCE of 15.39% with simultaneously improved voltage (0.845 V) and fill factor (75.02%), which is much higher than 14.66% of TA treatment. Moreover, 15.39% efficiency is also the highest value in binary ASM‐OSCs. [ABSTRACT FROM AUTHOR]

Currently, the performance improvement for inverted perovskite solar cells (PVSCs) is mainly limited by the high open circuit voltage (VOC) loss caused by detrimental non‐radiative recombination (NRR) processes. Herein, we report a simple and efficient way to simultaneously reduce the NRR processes inside perovskites and at the interface by rationally designing a new pyridine‐based polymer hole‐transporting material (HTM), PPY2, which exhibits suitable energy levels with perovskites, high hole mobility, effective passivation of the uncoordinated Pb2+ and iodide defects, as well as the capability of promoting the formation of high‐quality polycrystalline perovskite films. In absence of any dopants, the inverted PVSCs using PPY2 as the HTM deliver an encouraging PCE up to 22.41 % with a small VOC loss (0.40 V), among the best device performances for inverted PVSCs reported so far. Furthermore, PPY2‐based unencapsulated devices show an excellent long‐term photostability, and over 97 % of its initial PCE can be maintained after one sun constant illumination for 500 h. [ABSTRACT FROM AUTHOR]

The presence of non‐radiative recombination at the perovskite surface/interface limits the overall efficiency of perovskite solar cells (PSCs). Surface passivation has been demonstrated as an efficient strategy to suppress such recombination in Si cells. Here, 1‐naphthylmethylamine iodide (NMAI) is judiciously selected to passivate the surface of the perovskite film. In contrast to the popular phenylethylammonium iodide, NMAI post‐treatment primarily leaves NMAI salt on the surface of the perovskite film. The formed NMAI layer not only efficiently decreases the defect‐assisted recombination for chemical passivation, but also retards the charge accumulation of energy level mis‐alignment for vacuum level bending and prevents minority carrier recombination due to the charge‐blocking effect. Consequently, planar PSCs with high efficiency of 21.04% and improved long‐term stability (98.9% of the initial efficiency after 3240 h) are obtained. Moreover, open‐circuit voltage as high as 1.20 V is achieved at the absorption threshold of 1.61 eV, which is among the highest reported values in planar PSCs. This work provides new insights into the passivation mechanisms of organic ammonium salts and suggests future guidelines for developing improved passivation layers. [ABSTRACT FROM AUTHOR]

Defect passivation has been demonstrated to be effective in improving the radiative recombination of charge carriers in perovskites, and consequently, the device performance of the resultant perovskite light‐emitting diodes (LEDs). State‐of‐the‐art useful passivation agents in perovskite LEDs are mostly organic chelating molecules that, however, simultaneously sacrifice the charge‐transport properties and thermal stability of the resultant perovskite emissive layers, thereby deteriorating performance, and especially the operational stability of the devices. We demonstrate that lithium halides can efficiently passivate the defects generated by halide vacancies and reduce trap state density, thereby suppressing ion migration in perovskite films. Efficient green perovskite LEDs based on all‐inorganic CsPbBr3 perovskite with a peak external quantum efficiency of 16.2 %, as well as a high maximum brightness of 50 270 cd m−2, are achieved. Moreover, the device shows decent stability even under a brightness of 104 cd m−2. We highlight the universal applicability of defect passivation using lithium halides, which enabled us to improve the efficiency of blue and red perovskite LEDs. [ABSTRACT FROM AUTHOR]

The move toward lower cost sources of solar silicon has intensified the efforts to investigate the possibilities of passivating or reducing the recombination activity caused by deep states associated with transition metals. This is particularly important for the case of the slow diffusing metals early in the periodic sequence which are not removed by conventional gettering. In this paper, we examine reactions between hydrogen and transition metals and discuss the possibility of such reactions during cell processing. We analyse the case of hydrogenation of iron in p-type Si and show that FeH can form under non-equilibrium conditions. We consider the electrical activity of the slow diffusing metals Ti, V, and Mo, how this is affected in the presence of hydrogen, and the stability of TM-H complexes formed. Finally, we discuss recent experiments which indicate that re-siting of some transition metals from the interstitial to substitutional site is possible in the presence of excess vacancies, leading to a reduction in recombination activity. Periodic ordering of the 3d, 4d, and 5d transition metals with adjacent columns of the periodic table. The metals with hydrogen complexes which have had their electronic properties reported in the literature or in this paper are highlighted in green. [ABSTRACT FROM AUTHOR]

Effect of an internal built-in electric field on the non-radiative recombination process of strain-balanced InGaAs/GaAsP multiple quantum wells (MQWs) inserted into a GaAs p- i- n solar cell structure was investigated using the piezoelectric photo-thermal technique. From the experimental data obtained from two types of p- i- n solar cell structures with partly charge-neutral and uniform-gradient potentials, the decrease in the built-in electric field contributed to the decrease in the non-radiative carrier recombination in the MQW. This phenomenon was especially pronounced in the higher photon energy of the incident light and in large quantum well stack number. With the increase in the photon energy, the penetration length shortened, and most carriers were generated in the charge-neutral area in the i-region. The present experimental results could be understood by the increase in the radiative recombination processes within the MQW because of the wave function overlap is essentially unity. [ABSTRACT FROM AUTHOR]