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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]

Interface defect is one of the main factors that lead to non-radiative recombination of carriers at the interface and the decomposition of perovskites. This ultimately results in low efficiency and poor stability of perovskite solar cells (PSCs). Here, a passivated molecule called 2-Aminopyridine (2-APy) was proposed to reduce the defects of the interface between the perovskite and the hole transport layer. The results showed that the amino group in 2-aminopyridine can interact with the vacancy and free iodide ions on the surface of perovskite, thus passivating the defects at the interface and enhancing the hole transport capacity. As a result, 2-APy-modified PSCs exhibited inhibited non-radiative recombination, and the efficiency of PSCs increased to 21.46 %. The increase in the efficiency of PSCs is primarily seen in the rise of the open circuit voltage (V OC , from 1.12 to 1.15 V) and short circuit current (J SC , from 22.86 to 23.77 mA/cm2). This work demonstrates that pyridine is an effective group for passivating the defects between the perovskite layer and the hole transport layer. [ABSTRACT FROM AUTHOR]

[Display omitted] • P(VDF-TRFE) boosts Spiro-OMeTAD-based power conversion efficiency (PCE) to 24.1%. • P(VDF-TRFE)-integrated cells retain > 90 % PCE for 45 days under ambient conditions. • P(VDF-TRFE)-integrated cells retained 94% PCE after 1080-hour light-soaking. • Robust bonding between P(VDF-TRFE) and Li-TFSI/TBP enhances HTL film quality. This study demonstrates the transformative impact of incorporating poly(vinylidene fluoride-co-trifluoroethylene) P(VDF-TRFE) as an additive in the hole transport layer (HTL) of 2,2′,7,7′-Tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (Spiro-OMeTAD). The P(VDF-TRFE) additive forms resilient coordination bonds with 4- tert -butylpyridine (TBP) and lithium bis(trifluoromethanesulfonyl)imide additives, which mitigates TBP evaporation and improves Spiro-OMeTAD film quality. In addition, we observed improvements in solar cell current–voltage characteristics consistent with increased Spiro-OMeTAD conductivity and suppressed non-radiative recombination at the HTL/perovskite interface. P(VDF-TRFE)-integrated devices exhibit an increment in power conversion efficiency (PCE) up to 24.1 % (reverse scan) from a reference PCE of 21.4 %. Furthermore, the unencapsulated P(VDF-TRFE)-integrated devices demonstrate improved stability, retaining over 90 % PCE after 45 days in an ambient atmosphere in the dark and 94 % PCE after 1080 h of continuous light-soaking in a nitrogen environment. This work demonstrates how additive engineering, as exemplified by P(VDF-TRFE), can effectively address stability and performance challenges within Spiro-OMeTAD in perovskite solar cells. [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]

Self-assembled GaN nanorods were grown by metal-organic chemical vapor deposition. A highly regular rosette-shaped cathodoluminescence pattern in the GaN nanorods is observed, where its origin is helpful to deepen the understanding of GaN nanorod growth. The pattern forms at the very early stages of nanorod growth, which consists of yellow luminescence at the edges and the non-luminous region at six vertices of the hexagon. To clarify its origin, we carried out detailed cathodoluminescence studies, electron microscopy studies and nanoscale secondary ion mass spectrometry at both the nanorod surface and cross-section. We found the pattern is not related to optical resonance modes or polarity inversion, which are commonly reported in GaN nanostructures. After chemical composition and strain analysis, we found higher carbon and nitrogen cluster concentration and large compressive strain at the pattern area. The pattern formation may relate to facet preferential distribution of non-radiative recombination centers related to excess carbon/nitrogen. This work provides an insight into strain distribution and defect-related emission in GaN nanorod, which is critical for future optoelectronic applications. [ABSTRACT FROM AUTHOR]

Despite rapid advancements in power conversion efficiency in the last decade, perovskite solar cells still perform below their thermodynamic efficiency limits. Non-radiative recombination, in particular, has limited the external radiative efficiency and open circuit voltage in the highest performing devices. We review the historical progress in enhancing perovskite external radiative efficiency and determine key strategies for reaching high optoelectronic quality. Specifically, we focus on non-radiative recombination within the perovskite layer and highlight novel approaches to reduce energy losses at interfaces and through parasitic absorption. By strategically targeting defects, it is likely that the next set of record-performing devices with ultra-low voltage losses will be achieved. [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 possibility to manufacture perovskite solar cells (PSCs) at low temperatures paves the way to flexible and lightweight photovoltaic (PV) devices manufactured via high-throughput roll-to-roll processes. In order to achieve higher power conversion efficiencies, it is necessary to approach the radiative limit via suppression of non-radiative recombination losses. Herein, we performed a systematic voltage loss analysis for a typical low-temperature processed, flexible PSC in n-i-p configuration using vacuum deposited C60 as electron transport layer (ETL) and two-step hybrid vacuum-solution deposition for CH3NH3PbI3 perovskite absorber. We identified the ETL/absorber interface as a bottleneck in relation to non-radiative recombination losses, the quasi-Fermi level splitting (QFLS) decreases from ~1.23 eV for the bare absorber, just ~90 meV below the radiative limit, to ~1.10 eV when C60 is used as ETL. To effectively mitigate these voltage losses, we investigated different interfacial modifications via vacuum deposited interlayers (BCP, B4PyMPM, 3TPYMB, and LiF). An improvement in QFLS of ~30–40 meV is observed after interlayer deposition and confirmed by comparable improvements in the open-circuit voltage after implementation of these interfacial modifications in flexible PSCs. Further investigations on absorber/hole transport layer (HTL) interface point out the detrimental role of dopants in Spiro-OMeTAD film (widely employed HTL in the community) as recombination centers upon oxidation and light exposure. [ABSTRACT FROM AUTHOR]

Light-induced strategies are crucial for deciding the physical and chemical properties of organometal halide perovskite materials and their photovoltaic devices. Herein, the triple cation ((FA 0.83 MA 0.17) 0.95 Cs 0.05 Pb(I 0.83 Br 0.17) 3) hybrid perovskite films have been fabricated using a simple solution-processed method. These films were illuminated by blue light (417 nm) for different time durations and characterized for structural, surface morphological, optical, and charge carrier dynamics. Under illumination conditions, a reduction in lattice micro-strain has been observed. The enhanced optical absorbance and reduced non-radiative recombination have also been monitored in light-illuminated perovskite films. Further, time-resolved photoluminescence (TRPL) and ultra-fast transient absorption spectroscopy (TAS) measurements have been performed to study the charge carrier dynamics. TRPL results show that the average lifetime of charge carriers has increased from 3 ns to 19 ns upon continuous light illumination conditions. Further, the recombination time of the charge carriers decreased from 226 ps to 66 ps upon continuous light illumination for 30 min. This study suggests that light-induced experiments on perovskite films can be utilized for micro-strain regulation and modulation of their charge carrier dynamics for future perovskite solar cell applications. [Display omitted] • Regulation of micro-strain of (FA 0.83 MA 0.17) 0.95 Cs 0.05 Pb(I 0.83 Br 0.17) 3 hybrid perovskite films due to light illumination. • The enhanced optical absorbance and reduced non-radiative recombination have also been monitored in light-illuminated perovskite films. • Relaxation of hot charge carriers from the high excited states to quasi-thermal equilibrium states has been observed by transient absorption spectra. [ABSTRACT FROM AUTHOR]

A set of OASs with various side chains are applied as passivators to regulate interfacial band alignment, decrease defect density, and increase hydrophobic property. As a consequence, PSCs passivated with TOAC bearing a Si-O-CH 3 side chain achieve an increase in stability and PCE from 16.66% to 20.55%. [Display omitted] • Studying passivation effects via using a set of OASs with various side chains. • TOAC bearing a Si-O-CH 3 side chain leads to superior defect passivation, interfacial band alignment and hydrophobic property. • TOAC-treated PSCs show an increase in mean PCE from 16.62% to 20.06%. • The unencapsulated PSCs with TOAC treatment achieve excellent high-humidity stability. The extreme vulnerability of hybrid perovskite solar cells (PSCs) to moisture greatly limits the realization of their full potential. Here, we propose an efficient strategy to reinforce the efficiency and the ambient stability of PSCs via employing a series of octadecyl ammonium salts (OASs): octadecyl trimethyl ammonium chloride (OTAC), octadecyl dimethyl benzyl ammonium chloride (ODBAC), and 3-(trimethoxysilyl)propyl octadecyldimethyl ammonium chloride (TOAC), as passivating agents. Among these OASs, TOAC bearing a trimethoxysilane (Si-O-CH 3) side chain group most efficiently promoted the efficiency along with the high-humidity stability of PSC devices. TOAC significantly passivated the defects, assisted better energy-level alignment and facilitated charge carrier transport in the devices. The TOAC-passivated PSCs exhibited an increase in the average PCE from 16.62 ± 0.56 % to 20.06 ± 0.68 % with a substantially enhanced fill factor of 80.10 ± 1.82 %. Furthermore, the unencapsulated TOAC-passivated PSCs preserved 90 % of their performance after storage in ambient conditions (25–30 ℃, 50–70 % relative humidity) for 300 h. When no OAS passivator was introduced, the devices were losing more than 74 % of their starting PCE after 150 h. The Si-O-CH 3 groups side-chained to the OAS molecules were capable of supporting superior protection to the PSC devices against the permeation of high-moisture. Thereupon, the application of multifunctional octadecyl ammonium salt molecules to passivate defects and tailor the interface energy-level alignment in PSCs offers an encouraging staging to upgrade the PV performance of PSCs. [ABSTRACT FROM AUTHOR]

Abstract High-efficiency semiconductor lasers and light-emitting diodes operating in the 3–5 μm mid-infrared (mid-IR) spectral range are currently of great demand for a wide variety of applications, in particular, gas sensing, noninvasive medical tests, IR spectroscopy etc. III-V compounds with a lattice constant of about 6.1 Å are traditionally used for this spectral range. The attractive idea to fabricate such emitters on GaAs substrates by using In(Ga,Al)As compounds is restricted by either the minimum operating wavelength of ∼8 μm in case of pseudomorphic AlGaAs-based quantum cascade lasers or requires utilization of thick metamorphic In x Al 1 -x As buffer layers (MBLs) playing a key role in reducing the density of threading dislocations (TDs) in an active region, which otherwise result in a strong decay of the quantum efficiency of such mid-IR emitters. In this review we present the results of careful investigations of employing the convex-graded In x Al 1 -x As MBLs for fabrication by molecular beam epitaxy on GaAs (001) substrates of In(Ga,Al)As heterostructures with a combined type-II/type-I InSb/InAs/InGaAs quantum well (QW) for efficient mid-IR emitters (3–3.6 μm). The issues of strain relaxation, elastic stress balance, efficiency of radiative and non-radiative recombination at T = 10–300 K are discussed in relation to molecular beam epitaxy (MBE) growth conditions and designs of the structures. A wide complex of techniques including in-situ reflection high-energy electron diffraction, atomic force microscopy (AFM), scanning and transmission electron microscopies, X-ray diffractometry, reciprocal space mapping, selective area electron diffraction, as well as photoluminescence (PL) and Fourier-transformed infrared spectroscopy was used to study in detail structural and optical properties of the metamorphic QW structures. Optimization of the growth conditions (the substrate temperature, the As 4 /III ratio) and elastic strain profiles governed by variation of an inverse step in the In content profile between the MBL and the InAlAs virtual substrate results in decrease in the TD density (down to 3 × 107 cm−2), increase of the thickness of the low-TD-density near-surface MBL region to 250–300 nm, the extremely low surface roughness with the RMS value of 1.6–2.4 nm, measured by AFM, as well as rather high 3.5 μm-PL intensity at temperatures up to 300 K in such structures. The obtained results indicate that the metamorphic InSb/In(Ga,Al)As QW heterostructures of proper design, grown under the optimum MBE conditions, are very promising for fabricating the efficient mid-IR emitters on a GaAs platform. [ABSTRACT FROM AUTHOR]

• Interfacial molecular stacking is optimized by a symmetric DDS molecule. • The DDS exhibits defect passivation capability and hydrophobicity. • A suitable intermediate energy level is achieved by DDS modification at the interface. • Carrier transfer and extraction are promoted by the DDS interlayer. • The PCE increases from 21.05% to 24.02% with a high fill factor of 84.0%. The non-radiative charge carrier recombination loss at the surface and interface of the perovskite layers in perovskite solar cells (PSCs) is the main cause of their limited power conversion efficiency (PCE). Here we propose an efficient strategy to minimize the non-radiative recombination by introducing symmetric molecules with regular arrangement at the interface between the perovskite layer and hole transport layer (HTL). One end of the symmetric molecule gets in a close contact with the terminal groups of the molecules in the HTL, while the other end promotes connection with the perovskite, resulting in an enhanced interfacial electrical contact and a better valence band energy-level alignment for efficient hole extraction. In contrast, introducing similar but asymmetrical molecules forms a dimer structure and mismatched energy levels at the interface region, which is detrimental to the carrier transport. The best-performing planar PSC with the symmetric molecular modification exhibited an increase in the PCE from 21.05% to 24.02% with a substantially enhanced fill factor of 84.0%, which can be ascribed to the synergistic effects of surface defect passivation and reduction in the interfacial energy barrier. Furthermore, the corresponding unencapsulated PSC retained 80% of the original PCE after 4,000 h of aging in dry air. [ABSTRACT FROM AUTHOR]

Organic solar cells benefit from non-fullerene acceptors (NFA) due to their high absorption coefficients, tunable frontier energy levels, and optical gaps, as well as their relatively high luminescence quantum efficiencies as compared to fullerenes. Those merits result in high yields of charge generation at a low or negligible energetic offset at the donor/NFA heterojunction, with efficiencies over 19% achieved for single-junction devices. Pushing this value significantly over 20% requires an increase in open-circuit voltage, which is currently still well below the thermodynamic limit. This can only be achieved by reducing non-radiative recombination, and hereby increasing the electroluminescence quantum efficiency of the photo-active layer. Here, current understanding of the origin of non-radiative decay, as well as an accurate quantification of the associated voltage losses are summarized. Promising strategies for suppressing these losses are highlighted, with focus on new material design, optimization of donor-acceptor combination, and blend morphology. This review aims at guiding researchers in their quest to find future solar harvesting donor-acceptor blends, which combine a high yield of exciton dissociation with a high yield of radiative free carrier recombination and low voltage losses, hereby closing the efficiency gap with inorganic and perovskite photovoltaics., (© 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

The extent of subsurface damage on (0001) GaN wafers post different polishing treatments was quantified using depth-resolved cathodoluminescence spectroscopy (DRCLS). The band edge emission spectra were obtained from CLS with different electron energies, which manifested a significant non-radiative recombination resulted from polishing-induced subsurface damage. Cross-sectional transmission electron microscopy (XTEM) was also used to diagnose the extent of the subsurface damage layer. For the GaN polished with 1.00 and 0.25 μm diamonds abrasive, the extent of non-radiative subsurface damage is about 250 and 100 nm, corresponding to the calculated electron penetration depth at the accelerating voltage for the onset of band edge emission. In this study, the depth of subsurface damage estimated from CL spectra compared well with direct XTEM measurements in GaN substrate. [ABSTRACT FROM AUTHOR]

Lead chalcogenide colloidal quantum dot solar cells (CQDSCs) have the potential to revolutionize the field of light-to-electricity conversion with their exceptional optoelectronic properties. Unfortunately, realizing their full potential has been hindered by persistent and poorly understood limitations in fill factor (FF) and open-circuit voltage (V oc) losses. In this study, we performed a systematic numerical analysis of practical PbS CQDSCs to identify the root causes of FF and V oc losses in the current development stage, and to provide a clear and feasible roadmap for achieving a PCE of more than 20% in future development stages. Our analysis revealed that the highly effective route for enhancing the current 10% device is to initially modify the internal resistances, resulting in a significant reduction in FF losses to 15%, followed by systematic optimization of surface recombination velocities in the absorber layer and the absorber/hole transfer layer (HTL) interface, which can generate a V oc improvement of 3.76%, ultimately leading to a near-15% PCE. To further elevate PCE to unprecedented heights, we identified the precise regulation of surface excess charge densities at the absorber/HTL interface and the HTL/back contact interface as critical factors. By finely tuning these performance-limiting factors, we demonstrated the feasibility of achieving over 20% PCE, with minimal V oc loss of 318.10 mV and almost negligible FF loss of 6.08% in PbS CQDSCs. Our investigation provides crucial insights into the causes of FF and V oc losses in PbS CQDSCs and offers a clear pathway for future progress in this rapidly evolving field. [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]

With the modulation of halogen of phenylethylamine, more stabilized tin halide perovskite and efficient charge transfer around the I-site and PEA+ mocule are achieced. The corresponding device achieves a notable improved power conversion efficiency of 11.94% with superior operational stability. [Display omitted] • Halogen engineering of phenylethylamine in tin halide perovskite was investigated. • Introduction of PEABr-I reduced the residual strain and stabilized the lattice. • The halide engineering decreased the formation energy of overall 2D/3D structure. • The target devices obtained a PCE of 11.94 % and a V oc of 0.81 V. • The unencapsulated devices showed superior operational stability. Stability is one of the key factors limiting the development of lead-free tin halide perovskite solar cells (TPSCs). Large organic bulky phenethylammonium ions (PEA+) have been widely introduced in TPSCs to regulate the dimensionality and film growth of perovskite. However, the mismatch in ionic radius of halogen ions could compromise the structural stability. Here, we report the halogen engineering of bulky additives in tin perovskites and their effect on the lattice stability and device performance. It was revealed that partial substitution of PEAI with PEABr could improve the structural stability as well as the charge transfer by the density functional theory calculations. A reduced residual strain along the (h 00) planes and improved crystallinity was observed after the introduction of PEABr. The halogen engineering reduced the defect density remarkably and inhibited the non-radiative recombination. As a consequence, the target inverted FA 0.75 MA 0.25 SnI 2.75 Br 0.25 (FA = formamidinium, MA = methylammonium) TPSCs obtained a power conversion efficiency (PCE) of 11.94 % with an open-circuit voltage (V oc) of 0.81 V, which was significantly higher than that of the device in absence of PEABr (PCE of 9.79 % and V oc of 0.75 V). Meanwhile, the unencapsulated devices maintained 94 % of the initial PCE after 2040 h storage in the N 2 atmosphere. [ABSTRACT FROM AUTHOR]

Thin films of CdSe-based core-shell type quantum dots (CdSe/CdZnS, CdSe/ZnS and CdSeTe/ZnS) deposited on glass substrate were found to undergo a reversible change in photoluminescence (PL) on exposure to ozone in concentrations as low as 0.1 ppm in air. PL decreased rapidly on adding ozone and fully recovered after changing back to pure air. The PL of the CdSe/ZnS quantum dots (QDs) was not quenched by pure oxygen, nitrogen, argon, carbon dioxide, and air containing hydrogen. A comparison of various CdSe-based core-shell type QDs with different emission colors showed that green-emitting QDs with smaller size were more sensitive to ozone, while red-emitting QDs (of larger size) were more resistant to high concentrations of ozone. The response time of the sensor (for a 90 % signal change) was in the order of 10-20 min. The reversible, reproducible and selective response to ozone at room temperature under atmospheric pressure suggested that these QDs have a great potential in terms of fluorescent sensing of ozone. [ABSTRACT FROM AUTHOR]

[Display omitted] • The 5PFP-Br is used as a double-interface passivator for PSCs. • The ETL with 5PFP-Br passivation has higher conductivity and electron mobility. • The perovskite with 5PFP-Br passivation has lower interfacial carrier defect state. • The PCE of the treated device increased from 18.09% to 21.15%. • The device based 5PFP-Br double-interface passivator have good stability. In order to obtain high power conversion efficiency and high stability perovskite solar cells, many innovative optimization schemes have been proposed. Thereinto, the interface modification become an effective way to improve the performance of device. Here, A dual-interface passivation by 2, 3, 4, 5, 6-pentafluorophenylammonium bromide-based (5PFP-Br) is used to optimize the performance of device with the structure of ITO/SnO 2 /perovskite/PTAA/Ag. We design the 5PFP-Br layer at SnO 2 /perovskite and perovskite/PTAA interface respectively. The results show that the interface contact between perovskite and charge transport layer is improved obviously. At the same time, the density of carrier transport defect states in the device is reduced, thus reducing the non-radiative recombination of carriers. Meanwhile, the 5PFP-Br layer at perovskite/PTAA interface can effectively passivate Pb defects and reduce the number of grain boundaries in perovskite film, and increase the carrier transfer and collection efficiency. Finally, 5PFP-Br double-interface passivation can further optimize and improve the performance of device. The device based 5PFP-Br double-interface passivation presents an increased efficiency from 18.09% to 21.15%, where FF is raised from 73.30% to 80.04%. At the same time, unpackaged device can still be maintained to more than 90% efficiency after about 1200 h at 25 °C and 25%RH. [ABSTRACT FROM AUTHOR]

The photovoltaic performance of C/O/S-doped hexagonal boron nitride (h-BN) quantum dots (QDs) is studied using density functional theory. Doping leads to occupied or unoccupied midgap states in h-BN QDs, resulting in a redshift in their absorption spectra. C-doping provides better charge transfer capability than S/O-doping. In addition, C-doping reduces the open-circuit voltage, light collection efficiency, fill factor, and driving forces of electron injection and reduction of h-BN QD. However, the fast non-radiative recombination deteriorates the energy conversion of C-doped h-BN QDs. The current study provides evidence for the rational design of photocatalytic devices based on h-BN QDs. [Display omitted] • S- and O-doping are not adequate for improving energy conversion of h-BN QDs. • C-doping offers suitable energy levels for the energy conversion of h-BN QDs • C-doping lowers the photovoltaic performance of h-BN QDs. [ABSTRACT FROM AUTHOR]

Suppressing the photon energy loss (E loss ), especially the non-radiative loss, is of importance to further improve the device performance of organic solar cells (OSCs). However, typical π-conjugated semiconductors possess a large singlet-triplet energy gap (ΔE ST ), leading to a lower triplet state than charge transfer state and contributing to a non-radiative loss channel of the photocurrent by the triplet state. Herein, a series of triplet polymer donors are developed by introducing a BNIDT block into the PM6 polymer backbone. The high electron affinity of BNIDT and the opposite resonance effect of the BN bond in BNIDT results in a lowered highest occupied molecular orbital (HOMO) and a largely reduced ΔE ST . Moreover, the morphology of the active blends is also optimized by fine-tuning the BNIDT content. Therefore, non-radiative recombination via the terminal triplet loss channels and morphology traps is effectively suppressed. The PNB-3 (with 3% BNIDT):L8-BO device exhibits both small ΔE ST and optimized morphology, favoring more efficient charge transfer and transport. Finally, the simultaneously enhanced V oc of 0.907 V, J sc of 26.59 mA cm -2 , and FF of 78.86% contribute to a champion PCE of 19.02%. Therefore, introducing BN bonds into benchmark polymers is a possible avenue toward higher-performance of OSCs., (© 2023 Wiley-VCH GmbH.)

Functional passivators are conventionally utilized in modifying the crystallization properties of perovskites to minimize the non-radiative recombination losses in perovskite light-emitting diodes (PeLEDs). However, the weak anchor ability of some commonly adopted molecules has limited passivation ability to perovskites and even may desorb from the passivated defects in a short period of time, which bring about plenty of challenges for further development of high-performance PeLEDs. Here, a multidentate molecule, formamidine sulfinic acid (FSA), is introduced as a novel passivator to perovskites. FSA has multifunctional groups (S≐O, C≐N and NH 2 ) where the S≐O and C≐N groups enable coordination with the lead ions and the NH 2 interacts with the bromide ions, thus providing the most effective chemical passivation for defects and in turn the formation of highly stable perovskite emitters. Moreover, the interaction between the FSA and octahedral [PbBr 6 ] 4- can inhibit the formation of unfavorable low-n domains to further minimize the inefficient energy transfer inside the perovskite emitters. Therefore, the FSA passivated green-emitting PeLED exhibits a high external quantum efficiency (EQE) of 26.5% with fourfold enhancement in operating lifetime as compared to the control device, consolidating that the multidentate molecule is a promising strategy to effectively and sustainably passivate the perovskites., (© 2022 Wiley-VCH GmbH.)

Inverted perovskite solar cells (inverted-PSCs) have exhibited advantages of longer stability, less hysteresis, and lower fabrication temperature when compared to their regular counterparts, which are important for industry commercialization. Because of the great efforts that have been conducted in the past several years, the obtained efficiency of inverted-PSCs has almost caught up with that of the regular ones, 25.0% versus 25.7%. In this perspective, the recent studies on the design of high-performance inverted-PSCs based on diverse hole transport materials, as well as device fabrication and characterization are first reviewed. After that, the authors moved on to the interface and additive engineering that were exploited to suppress the nonradiative recombination. Finally, the challenges and possible research pathways for facilitating the industrialization of inverted-PSCs were envisaged., Competing Interests: The authors declare no conflicts of interest., (© 2023 The Authors. Exploration published by Henan University and John Wiley & Sons Australia, Ltd.)

A facile Lewis base thiourea (TU) is introduced into the tin perovskite precursor to form a SnI 2 -TU intermediate to guide the crystallization kinetics, delivering a remarkably improved PCE and stability in tin halide perovskite solar cells. [Display omitted] • Thiourea was applied to form a SnI 2 -TU intermediate to guide the crystallization kinetics. • The film morphology was improved and the non-radiative recombination is suppressed. • These benefits delivered a PCE of over 10% in inverted tin perovskite solar cells. • The unencapsulated device retained 90% of the initial efficiency after 1600 h in N 2 atmosphere. Tin halide perovskite is the most prospective lead-free perovskite material due to its close to ideal band gap and similar optoelectronic properties to the lead counterparts. Nevertheless, the lack of a regulated crystallization process leads to considerable defects and pinholes in those tin perovskite films, further deteriorating the achievable power conversion efficiency (PCE) for related solar cells. Herein, we employed a facile Lewis base thiourea (TU) into the perovskite precursor to form a SnI 2 -TU as an intermediate adduct to guide the crystallization kinetics, where the interaction between SnI 2 and TU was detected by Fourier transform infrared (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements, respectively. Improving the perovskite morphology with TU contributed to significant suppression of the non-radiative recombination and fast charge extraction through carrier dynamics analysis. These benefits delivered a remarkable PCE of over 10% in inverted tin perovskite solar cells, which was 24% higher than the original device. The unencapsulated device with TU retained 90% of the initial efficiency after over 1600 h in N 2 atmosphere. [ABSTRACT FROM AUTHOR]

Grain interiors (GIs) and grain boundaries (GBs) of perovskites have been investigated using chemically, spatially, and temporally resolved measurements. Two dimensional (2D) chemical mapping measurements revealed the GBs consisted of the non-stoichiometric PbI x or CH 3 NH 3 PbI x , that were characterized by an absence of chloride, an enriched oxygen concentration, and a high density of iodide vacancies. In addition, steady-state 2D photoluminescence showed the bandgap broadening at the GBs while 2D lifetime mapping measurement suggested that the GBs indeed contained deep defect centers. However, it is found that defective GBs in perovskite materials do not act as high recombination sites for photogenerated charge carriers due to the bandgap broadening of non-stoichiometric PbI x or CH 3 NH 3 PbI x perovskites at the GB that forms the potential barriers for photo-generated charge carriers toward the GBs. As a consequence, the photo-generated charge carriers adjacent to the GBs will be easily repelled by the GBs, resulting in a greater reduction of the recombination of photogenerated charge carriers. This is one possible reason for the high performance of CH 3 HN 3 PbI 3-x Cl x based solar cells. [ABSTRACT FROM AUTHOR]

ZnO nano/micro-rods on Zn foil are fabricated through a simple, low-cost, catalyst- and seed-free solvothermal method by using Zn foil as the Zn 2+ source and substrate in the sodium hydroxide solution. ZnO nano/micro-rods, which show good crystalline quality and grow along the c-axis, are distributed randomly on the Zn substrate and approximately perpendicular to the Zn substrate. Through analyzing the evolution of peak position and intensity of band gap emission with the temperature, two different non-radiative recombination processes are obtained. At low temperature the main non-radiative process is the thermal effect while at high temperature the main nonradiative process is the thermal escape from the structural defects assisted by LO phonon scattering. The understanding of the non-radiative recombination processes in ZnO nano/micro-rods on Zn foil might provide meaningful information for their potential application in the optoelectronic field. [ABSTRACT FROM AUTHOR]

This paper presents an extensive analysis of the degradation of UV-A light-emitting diodes (LEDs) submitted to constant current stress. The study is based on combined electrical, optical, and thermal measurements and demonstrates the following results: 1) the UV-A LEDs submitted to constant current stress show a gradual degradation, and the degradation rate is strongly dependent on the emission wavelength; 2) the degradation process is ascribed to the generation of point defects within the active region of the devices, with a subsequent increase in the nonradiative recombination rate; and 3) the time to degradation is strongly dependent on the stress current level and is thermally activated (activation energy equal to 0.36 eV). [ABSTRACT FROM PUBLISHER]

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[Display omitted] • A piperidine-based modulator ClEP was designed to passivate multi-type defects in MAFA perovskites. • The multifunctional ClEP helps perovskites crystallize in printable mesoscopic perovskite solar cells. • The performance of ClEP-modified printable mesoscopic PSCs is increased to 17.08% due to the better crystallization and less defects. Printable mesoscopic perovskite solar cells (PSCs) have received extensive attention due to their convenient large-area fabrication and good stability. The further improvement of the power conversion efficiency (PCE) of such simplified PSC configuration is limited by the low open circuit voltage (V OC). The high density of defects at grain boundaries of perovskites inside the mesoporous scaffold can cause severe nonradiative recombination, which have negative effects on V OC. Additive engineering has demonstrated advantages in improving the perovskite crystallization inside the pores, passivating the defects of perovskite and enhancing the performance of printable mesoscopic PSCs. Herein, we introduce a multifunctional modulator 1-(2-Chloroethyl) piperidine hydrochloride (ClEP) as an additive into the perovskite precursor solution. Benefiting from the strong interaction between ClEP and perovskite, it can interact with non-coordinating ions and defect states to achieve multi-defect passivation. As a result, the V OC of the printable mesoscopic PSC increases from 895.25 mV to 982.24 mV and the ClEP-treated printable mesoscopic PSC reaches a champion PCE of 17.08%. This work provides a new approach for developing efficient printable mesoscopic PSCs. [ABSTRACT FROM AUTHOR]