Chen Weijie

Metal (titanium or Ti) nanopillar arrays (NaPAs), vertically protruding on a TiO₂ compact layer, function as an electron transporting layer in perovskite solar cells. Ti NaPA has highly hydrophilic surfaces passivated with TiO₂, high electron mobility, and low work function; hence it compensates the loss of light harvesting in perovskite and leads to highly efficient, antiaging photovoltaic performance.

Abstract

Electron transporting layers (ETLs), required to be optically transparent in perovskite solar cells (PSCs) having regular structures, possess a determinant effect on electron extraction and collection. Metal oxides (e.g., TiO₂) have overwhelmingly served as ETLs, but usually have low electron mobility (μ_e < 10⁻² cm² V⁻¹ s⁻¹) not favorable for photovoltaic conversion. Here, metal oxides are replaced with metals (e.g., Ti with μ_e ≈ 294 cm² V⁻¹ s⁻¹) that are sculptured via glancing angle deposition to be a close‐packed nanopillar array (NaPA), which vertically protrudes on a transparent electrode to obtain sufficient optical transmission for light harvesting in perovskite. Ti NaPAs, whose rough surfaces are passivated with 5 nm thick TiO₂ (i.e., Ti NaPAs@TiO₂) to suppress exciton recombination, lead to the champion power conversion efficiency (PCE) of 18.89% that is superior to that of MAPbI₃ PSCs without Ti NaPAs@TiO₂ or containing TiO₂ NaPAs@TiO₂, owing to high surface wettability, high μ_e, and relatively low work function of Ti. Furthermore, Ti NaPAs@TiO₂ effectively prevents the decomposition of MAPbI₃ to achieve long‐term shelf stability whereby 50‐day aging only causes 15% PCE degradation. This work paves the way toward widening the material spectrum, from semiconductors to metals, to generate a diverse range of ETLs for producing efficient optoelectronic devices with long‐term shelf stability.

A novel strategy to neutralize charged point defects in organic‐inorganic hybrid perovskite materials is proposed for highly efficient and stable perovskite solar cells by using a zwitterionic L‐alanine additive, which can be passivated simultaneously with both positively and negatively charged defects because it contains both anion and cation functional groups in one molecule.

Abstract

Ionic defects (e.g., organic cations and halide anions), preferably residing along grain boundaries (GBs) and on perovskite film surfaces, are known to be a major source of the notorious environmental instability of perovskite solar cells (PeSCs). Although passivating ionic defects is desirable, previous approaches using Lewis base or acid molecules as additives suppress only the negatively or positively charged defects, thus leaving oppositely charged defects. In this work, both the cationic and anionic defects inside methyl ammonium lead tri‐iodide (MAPbI₃) are simultaneously passivated by introducing a zwitterionic form of the amino acid, L‐alanine, into the precursor solution as an additive. L‐alanine has both positive (NH₃ ⁺) and negative (COO⁻) functional groups at a specific solvent pH, thereby passivating both the cation and anion defects in MAPbI₃. The addition of L‐alanine increases the grain size of the perovskite crystals and lengthens the charge carrier lifetime (τ > 1 µs), leading to improved power conversion efficiencies (PCEs) of 20.3% (from 18.3% without an additive) for small‐area (4.64 mm²) devices and 15.6% (from 13.5%) for large‐area submodules (9.06 cm²). More importantly, the authors’ approach also significantly enhances the shelf storage and photoirradiation stabilities of PeSCs.

A low parasitic absorption with high thickness‐insensitivity feature can be concurrently achieved with the incorporation of zirconium (Zr) element into ZnO thin film (ZnO:Zr). Moreover, optimized surface morphology and enhanced electron conductivity are proposed in ZnO:Zr film. Indeed, ZnO:Zr electron transporting layers (ETL) boost the photovoltaic performance up to 17.2% with an improvement over 9% than that of pristine ZnO‐based devices (15.7%).

Abstract

Solution‐processed zinc oxide (ZnO) is one of the widely used electron transporting layers (ETLs) for organic solar cells (OSCs). However, low optical transparency along with thickness‐sensitivity of ZnO ETL constrains the improvement of photovoltaic performance and large‐scale fabrication compatibility. To resolve these issues, zirconium (Zr) doping is applied to tailor the optoelectronic and morphological properties of ZnO layer. This approach not only improves light transmittance with the suppressed parasitic absorption, but also provides an optimized surface morphology for enhancing charge extraction property and reducing potential of charge trap‐assisted recombination. By using ZnO:Zr as ETL in inverted device configuration, the maximum power conversion efficiency (PCE) of PM6:Y6:PC₇₁BM solar cell devices is up to 17.2%, which makes an enhancement of 9.55% compared to ZnO‐based devices (15.7%). As the thickness of ZnO:Zr ETL increases to ≈60 nm, the presence of the lower parasitic absorption together with uniform surface morphology can help photovoltaic performance maintain above 15%, which is beyond the performance of the pristine ZnO‐based device achieving only 11.9%. Such superiority of ZnO:Zr ETL is also validated by a series of well‐known BHJ systems, where in comparison with the devices based on pristine ZnO ETL, a better photovoltaic performance from ZnO:Zr device can be achieved.

Chlorination of the β‐position of benzo[1,2‐b:4,5‐c′]dithiophene‐4,8‐dione can enhance the intermolecular interaction. Single‐crystal analysis demonstrates that TTO‐Cl‐β exhibits the smallest π‐π stacking distance of 3.23 Å, much smaller than that of TTO‐Cl‐α and TTO. Accordingly, PBBD‐Cl‐β based on TTO‐Cl‐β achieved an outstanding power conversion efficiency (PCE) of 16.20%, providing a new insight for the design of acceptor units.

Abstract

The position of a chlorine atom in a charge carrier of polymer solar cells (PSCs) is important to boost their photovoltaic performance. Herein, two chlorinated D‐A conjugated polymers PBBD‐Cl‐α and PBBD‐Cl‐β are synthesized based on two new building blocks (TTO‐Cl‐α and TTO‐Cl‐β) respectively by introducing the chlorine atom into α or β position of the upper thiophene of the highly electron‐deficient benzo[1,2‐b:4,5‐c′]dithiophene‐4,8‐dione moiety. Single‐crystal analysis demonstrates that the chlorine‐free TTO shows a π‐π stacking distance (d _π‐π) of 3.55 Å. When H atom at the α position of thiophene of TTO is replaced by Cl, both π‐π stacking distance (d _π‐π = 3.48 Å) and Cl···S distance (d _Cl‐S = 4.4 Å) are simultaneously reduced for TTO‐Cl‐α compared with TTO. TTO‐Cl‐β then showed the Cl···S non‐covalent interaction can further shorten the intermolecular π‐π stacking separation to 3.23 Å, much smaller than that of TTO‐Cl‐α and TTO. After blending with BTP‐eC9, PBBD‐Cl‐β:BTP‐eC9‐based PSCs achieved an outstanding power conversion efficiency (PCE) of 16.20%, much higher than PBBD:BTP‐eC9 (10.06%) and PBBD‐Cl‐α:BTP‐eC9 (13.35%) based devices. These results provide an effective strategy for design and synthesis of highly efficient donor polymers by precise positioning of the chlorine substitution.

Self‐assembled P3HT‐COOH is an excellent hole extraction layer to fabricate robust, high‐performance, and extremely reproducible perovskite solar cells. The well‐aligned self‐assembled P3HT‐COOH generates a dipole layer between indium tin oxide and perovskite, substantially retarding interface charge recombination and producing highly sensitive devices to dim light. The enhanced crystallinity and preferred out‐of‐plane orientation play a key role to suppress the device degradation process.

Abstract

Crystallinity and crystal orientation have a predominant impact on a materials’ semiconducting properties, thus it is essential to manipulate the microstructure arrangements for desired semiconducting device performance. Here, ultra‐uniform hole‐transporting material (HTM) by self‐assembling COOH‐functionalized P3HT (P3HT‐COOH) is fabricated, on which near single crystal quality perovskite thin film can be grown. In particular, the self‐assembly approach facilitates the P3HT‐COOH molecules to form an ordered and homogeneous monolayer on top of the indium tin oxide (ITO) electrode facilitate the perovskite crystalline film growth with high quality and preferred orientations. After detailed spectroscopy and device characterizations, it is found that the carboxylic acid anchoring groups can down‐shift the work function and passivate the ITO surface, retarding the interface carrier recombination. As a result, the device made with the self‐assembled HTM show high open‐circuit voltage over 1.10 V and extend the lifetime over 4,300 h when storing at 30% relative humidity. Moreover, the cell works efficiently under much reduced light power, making it useful as power source under dim‐light conditions. The demonstration suggests a new facile way of fabricating monolayer HTM for high efficiency perovskite devices, as well as the interconnecting layer needed for tandem cell.

In this work, a perovskite solar cell (PSC) is fabricated via a scalable solution process under ambient conditions. A hysteresis‐free, high‐efficiency (21.1%), laminar‐air‐knife‐assisted meniscus coating of PSCs is demonstrated at room temperature and a relative humidity of 55%. An in‐depth in situ investigation by time‐resolved UV–vis spectroscopy is conduced to explore the nucleation dynamics.

Abstract

Extensive studies are conducted on perovskite solar cells (PSCs) with significant performance advances (mainly spin coating techniques), which have encouraged recent efforts on scalable coating techniques for the manufacture of PSCs. However, devices fabricated by blade coating techniques are inferior to state‐of‐the‐art spin‐coated devices because the power conversion efficiency (PCE) is highly dependent on the morphology and crystallization kinetics in the controlled environment and the delicate solvent system engineering. In this study, based on the widely studied perovskite solution system dimethylformamide–dimethyl sulfoxide, air‐knife‐assisted ambient fabrication of PSCs at a high relative humidity of 55 ± 5% is reported. In‐depth time‐resolved UV–vis spectrometry is carried out to investigate the impact of solvent removal and crystallization rate, which are critical factors influencing the crystallization kinetics and morphology because of adventitious moisture. UV–vis spectrometry enables accurate determination of the thickness of the wet precursor film. Anti‐solvent‐free, high‐humidity ambient coatings of hysteresis‐free PSCs with PCEs of 21.1% and 18.0% are demonstrated for 0.06 and 1 cm² devices, respectively. These PSCs exhibit comparable stability to those fabricated in a glovebox, thus demonstrating their high potential.

The addition of the correct amounts of dimethyl sulfoxide (DMSO) with 2‐methoxyethanol (2‐ME) perovskite precursor ink is a crucial step toward reproducible slot‐die coatings and highly efficient perovskite solar cells. Through observing the drying process of 2ME‐DMSO inks from in situ X‐ray diffraction experiments, it is demonstrated that 11.77 mol% DMSO favorably affects thin film growth.

Abstract

Solar cells incorporating metal‐halide perovskite (MHP) semiconductors are continuing to break efficiency records for solution‐processed solar cell devices. Scaling MHP‐based devices to larger area prototypes requires the development and optimization of scalable process technology and ink formulations that enable reproducible coating results. It is demonstrated that the power conversion efficiency (PCE) of small‐area methylammonium lead iodide (MAPbI₃) devices, slot‐die coated from a 2‐methoxy‐ethanol (2‐ME) based ink with dimethyl‐sulfoxide (DMSO) used as an additive depends on the amount of DMSO and age of the ink formulation. When adding 12 mol% of DMSO, small‐area devices of high performance (20.8%) are achieved. The effect of DMSO content and age on the thin film morphology and device performance through in situ X‐ray diffraction and small‐angle X‐ray scattering experiments is rationalized. Adding a limited amount of DMSO prevents the formation of a crystalline intermediate phase related to MAPbI₃ and 2‐ME (MAPbI₃‐2‐ME) and induces the formation of the MAPbI₃ perovskite phase. Higher DMSO content leads to the precipitation of the (DMSO)₂MA₂Pb₃I₈ intermediate phase that negatively affects the thin‐film morphology. These results demonstrate that rational insights into the ink composition and process control are critical to enable reproducible large‐scale manufacturing of MHP‐based devices for commercial applications.

High performance perovskite solar modules (PSMs) are fabricated by introducing NH₄Cl to induce the formation of the intermediate phases. The PSMs show long‐term operational stability with a T ₈₀ lifetime under continuous light illumination exceeding 1600 h for a 5 × 5 cm² solar module and 1100 h for a 10 × 10 cm² solar module.

Abstract

In addition to high efficiencies, upscaling and long‐term operational stability are key pre‐requisites for moving perovskite solar cells toward commercial applications. In this work, a strategy to fabricate large‐area uniform and dense perovskite films with a thickness over one‐micrometer via a two‐step coating process by introducing NH₄Cl as an additive in the PbI₂ precursor solution is developed. Incorporation of NH₄Cl induces the formation of the intermediate phases of x[NH₄ ⁺]·[PbI₂Cl _x ] ^{x −} and HPbI_{3− x} Cl _x , which can effectively retard the crystallization rate of perovskite leading to uniform and compact full‐coverage perovskite layers across large areas with high crystallinity, large grain sizes, and small surface roughness. The 5 × 5 and 10 × 10 cm² perovskite solar modules (PSMs) based on this method achieve a power conversion efficiency (PCE) of 14.55% and 10.25%, respectively. These PSMs also exhibit good operational stability with a T ₈₀ lifetime (the time during which the solar module PCE drops to 80% of its initial value) under continuous light illumination exceeding 1600 h (5 × 5 cm²) and 1100 h (10 × 10 cm²), respectively.

The significant advances in efficient photoabsorbent materials have been instrumental in the performance enhancement of semitransparent organic solar cells (ST‐OSCs) from <7% to 12–14% (with good visible transmittance) only in the last 3 years. This study reviews the progress of photoabsorbent materials for ST‐OSCs, and discusses the structure–property relationships and future perspectives for the development of multifunctional ST‐OSCs.

Abstract

Semi‐transparent organic solar cells (ST‐OSCs) have revolutionized the field of photovoltaics (PVs) due to their unique abilities, such as transparency and color tunability, and have transformed normal power‐harvesting OSC devices into multifunctional devices, such as building‐integrated photovoltaics, agrivoltaics, floating photovoltaics, and wearable electronics. Very recently, ST‐OSCs have seen remarkable progress, with a rapid increase in power conversion efficiency from below 7% to 12–14%, with an average visible transparency of 9–25%, especially due to the use of low bandgap semiconductors including polymer donors and non‐fullerene acceptors that exhibit absorption in the near‐infrared region as photoabsorbent materials. From this perspective, the latest developments in ST‐OSCs stemming from the innovations in photovoltaic materials that delivered multifunctional ST‐OSCs with top‐of‐the‐line power conversion efficiencies are discussed to shed light on the structure‐property relationship between molecular design and current challenges in this cutting‐edge research field. Finally, personal perspectives, including research directions for the future use of ST‐OSCs in multifunctional applications, are also proposed.

The controlled in situ fabrication of γ‐Rb _x Cs_{1– x} PbI₃ gradient‐alloyed quantum dots in polymeric films with tunable photoluminescence emission from 675 to 620 nm, full width at half maximum of 31 nm and quantum yields up to 91% for display backlight applications is reported here.

Abstract

Perovskite quantum dots are emerging as new generation functional materials for display applications. The issue of perovskite “red wall” has been an obstacle for their use in display technology. In this study, the fabrication of γ‐Rb _x Cs_{1– x} PbI₃ gradient‐alloyed quantum dots in polymeric matrix through a rational designed in situ fabrication process is reported. The formation of γ‐Rb _x Cs_{1– x} PbI₃ gradient‐alloyed structure can be explained by considering the lattice mismatch and solubility difference between γ‐CsPbI₃ and RbPbI₃. The photoluminescence emission of γ‐Rb _x Cs_{1– x} PbI₃ gradient‐alloyed quantum dots can be tuned from 675 to 620 nm with full width at half maximum of 31 nm and maximum quantum yields up to 91%. Importantly, the packaged films retained about 95% of its original photoluminescence intensity after 1000 h aging at the test conditions of 60 °C, 90% RH and 40 °C, 90% RH with 3 mW cm⁻², 455 nm blue light irradiation, respectively. By integrating a red and green dual emissive film with blue Mini LEDs, a LCD backlight of a color space of ≈130% of NTSC 1931 standard is achieved with matching rate of 100%.

The simultaneous improvement of the photocurrent and stability in organometal halide perovskite (OHP) photocathodes is successfully achieved by introducing both L‐proline zwitterion additives in perovskite materials and a eutectic gallium indium alloy as a contact material for metal passivation. This approach can be an innovative technique for achieving high‐performance OHP‐based photoelectrochemical devices.

Abstract

Although organometal halide perovskites (OHPs) have desirable photovoltaic properties, their photoelectrochemical (PEC) water‐splitting application for hydrogen production is limited by the instability originating from their intrinsic ionic defects and hygroscopic vulnerability. Herein, a highly efficient and stable OHP‐based photocathode achieved by a new zwitterion (L‐proline) passivation and a eutectic gallium indium alloy (EGaIn) encapsulation method is described. The zwitterion, which has both cations and anions, can simultaneously passivate both positively and negatively charged defects in OHPs. The resulting OHP photovoltaic cells with passivated shows an over 20% power conversion efficiency with an open‐circuit voltage of 1.13 V and a short‐circuit current of 22.13 mA cm⁻². The EGaIn‐incorporated Ti foil provides complete encapsulation from the external environment while maintaining good transport of photogenerated charges from OHPs. Thus, these photocathodes exhibit a remarkable average photocurrent density of 21.2 mA cm⁻² which has less than 5% current loss between PV cells and PEC cells. More admirably, the photocathode has the highest stability over 54 hours under continuous full sunlight illumination in a sulfuric acid electrolyte.

An anion/cation synergy strategy is proposed by the incorporation of ZnI₂ in CsPbI₃ quantum dots (QDs) to improve the stability and photoelectric properties. The obtained Zn:CsPbI₃ QDs show lower defect state density and enhanced structural stability. Perovskite quantum dot solar cells fabricated with Zn:CsPbI₃ QDs exhibit a champion power conversion efficiency over 16%.

Abstract

All‐inorganic CsPbI₃ quantum dots (QDs) have shown great potential in photovoltaic applications. However, their performance has been limited by defects and phase stability. Herein, an anion/cation synergy strategy to improve the structural stability of CsPbI₃ QDs and reduce the pivotal iodine vacancy (V _I) defect states is proposed. The Zn‐doped CsPbI₃ (Zn:CsPbI₃) QDs have been successfully synthesized employing ZnI₂ as the dopant to provide Zn²⁺ and extra I⁻. Theoretical calculations and experimental results demonstrate that the Zn:CsPbI₃ QDs show better thermodynamic stability and higher photoluminescence quantum yield (PLQY) compared to the pristine CsPbI₃ QDs. The doping of Zn in CsPbI₃ QDs increases the formation energy and Goldschmidt tolerance factor, thereby improving the thermodynamic stability. The additional I⁻ helps to reduce the V _I defects during the synthesis of CsPbI₃ QDs, resulting in the higher PLQY. More importantly, the synergistic effect of Zn²⁺ and I⁻ in CsPbI₃ QDs can prevent the iodine loss during the fabrication of CsPbI₃ QD film, inhibiting the formation of new V _I defect states in the construction of solar cells. Consequently, the anion/cation synergy strategy affords the CsPbI₃ quantum dot solar cells (QDSC) a power conversion efficiency over 16%, which is among the best efficiencies for perovskite QDSCs.

Low conductivity and hole mobility in the pristine metal phthalocyanines greatly limit their application in perovskite solar cells (PSCs) as the hole‐transporting materials (HTMs). Here, we prepare a Ni phthalocyanine (NiPc) decorated by four methoxyethoxy units as HTMs. In NiPc, the two oxygen atoms in peripheral substituent have a modified effect on the dipole direction, while the central Ni atom contributes more electron to phthalocyanine ring, thus efficiently increasing the intramolecular dipole. Calculation analyses reveal the extracted holes within NiPc are mainly concentrated on the phthalocyanine core induced by the intramolecular electric field, and further to be transferred by π‐π stacking space channel between NiPc molecules. Finally, the best efficiency of PSCs with NiPc as dopant‐free HTs realizes a record value of 21.23% (certified 21.03%). The PSCs also exhibit the good moisture, heating and light stabilities. This work provides a novel way to improve the performance of PSCs with free‐doped metal phthalocyanines as HTMs.

An organic‐inorganic hybrid electrolyte based on a cylic Ti‐oxo cluster as inorganic core and naphthalene based organic ammonium bromide salts as electrolyte was developed with easy synthesis and low cost. The new hybrid electrolyte exhibits excellent solubility in methanol, aligned work function, good conductivity and amorphous state in thin film, enabling its successful application as cathode interlayer into organic solar cells with a high‐power conversion efficiency of 17.19%. The studies in this work demonstrate that the hybrid electrolytes are a new kind of semiconductors, exhibiting promising application in organic electronics.

Two conjugated polymers with rigid planar backbones, but with disordered crystalline structures, exhibit surprising structural tolerance to commonly used n‐dopants. These properties allow both high concentrations and high mobility of the charge carriers to be realized simultaneously in n‐doped polymers, resulting in excellent electrical conductivity of over 90 S cm⁻¹ and thermoelectric performance up to 106 µW m⁻¹ K⁻².

Abstract

Solution‐processable highly conductive polymers are of great interest in emerging electronic applications. For p‐doped polymers, conductivities as high a nearly 10⁵ S cm⁻¹ have been reported. In the case of n‐doped polymers, they often fall well short of the high values noted above, which might be achievable, if much higher charge‐carrier mobilities determined could be realized in combination with high charge‐carrier densities. This is in part due to inefficient doping and dopant ions disturbing the ordering of polymers, limiting efficient charge transport and ultimately the achievable conductivities. Here, n‐doped polymers that achieve a high conductivity of more than 90 S cm⁻¹ by a simple solution‐based co‐deposition method are reported. Two conjugated polymers with rigid planar backbones, but with disordered crystalline structures, exhibit surprising structural tolerance to, and excellent miscibility with, commonly used n‐dopants. These properties allow both high concentrations and high mobility of the charge carriers to be realized simultaneously in n‐doped polymers, resulting in excellent electrical conductivity and thermoelectric performance.

Semi‐transparent organic solar cells (STOSCs) have received increasing attention due to promising applications such as building integrated photovoltaics. Successful commercialization requires that STOSCs are aesthetically pleasing as well as having balanced power conversion efficiencies (PCE) and average visible transmittances (AVTs). Non‐fullerene acceptors (NFAs), which possess excellent electrical/chemical properties, have helped STOSCs to achieve high PCE and AVT, however, research related to modulating the color and appearance of STOSCs has lagged behind. In this work, narrow band gap donor and acceptor (PTB7‐Th and IEICO‐4F) and ultra‐wide band gap acceptors (T2‐ORH and T2‐OEHRH) were employed to achieve semi‐transparency and controllable device coloration. We successfully demonstrated blend films with controllable colors including cyan → blue → purple → reddish purple colors, which were controlled by the ratios of IEICO‐4F:T2‐ORH or IEICO‐4F:T2‐OEHRH with PTB7‐Th. By incorporating semi‐transparent electrodes (comprising Sb₂O₃/Ag/Sb₂O₃), STOSCs with PCEs of 6—7% were achieved for cyan, aqua, indigo and purple and ∽4% PCEs for reddish‐purple colors, with AVTs in the range of 23—35%. Additionally, optical properties of blend films were studied via absorption and transmission measurements, while the range of colors achieved was quantified using commission internationale de l'éclairage (CIE) chromaticity and commission internationale de l'éclairage L* a* b* (CIELAB) color space then represented as red, green and blue (RGB) color models.

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Light harvesting is central to many photonic materials. The light harvesting efficiency in these materials is, however, generally reduced because upper excited‐state energy is lost by energy‐dissipating internal conversion and vibrational relaxation processes. Here, we report size‐dependent energy harvesting from nonthermalized, upper excited states of glutathione‐protected gold clusters of various size, including Au₁₈, Au₂₂, Au₂₅, Au₆₇, Au₁₀₂ and Au_∽940. Femtosecond transient absorption measurements have revealed that the internal conversion processes of Au₁₈, Au₂₂ and Au₂₅ are relatively slow that the upper excited‐state energy of gold cluster can efficiently be harvested by an energy acceptor, aminofluorescein (AF), covalently attached to gold cluster on the time scales of 150 fs (Au₁₈), 220 fs (Au₂₂) and 380 fs (Au₂₅). Steady‐state photoluminescence measurements of AF‐conjugated Au₁₈, Au₂₂, and Au₂₅ clusters show notable AF emission upon high energy excitation of gold clusters. This work opens up a new avenue for energy harvesting from nonthermalized upper excited states of gold clusters, which would otherwise be lost as heat.

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Capacitive response at long timescale seems to remain an elusive feature in the analysis of the electrical properties of perovskite‐based solar cells. It belongs to one of the critical anomalous effects that arises from the characteristic phenomenology of this type of emerging photovoltaic devices. Thereby, accurately deducing key capacitance feature of new light harvesting perovskites from electrical measurements represents a significant challenge regarding the interpretation of physical processes and the control of undesired mechanisms, such as slow dynamic effects and/or current density‐voltage (J–V) hysteresis. Here, it is shown that long timescale mechanisms that give rise to hysteresis in stable and high‐efficiency quadruple‐cation perovskites are not due to a classical capacitive behavior in the sense of ideal charge accumulation processes. Instead, it is a phenomenological consequence of slow memory‐based capacitive currents and the underlying cooperative relaxations. This work reveals that a fractional dynamics approach, based on the idea of capacitance distribution in perovskite devices, reliably models the slow transient phenomena and the consequent scan‐rate‐ and bias‐dependent hysteresis. Observable for a wide variety of photovoltaic halide perovskites, distributed capacitive effects are rather universal anomalous phenomena, which can be related to the long‐time electrical response and hysteresis.

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The possible side reaction in the lead iodide solution of formamidinium is studied, and phenylboric acid (PBA) is introduced as a stabilizer in the perovskite precursor solution, which can inhibit the side reaction, thus greatly improving the stability of the perovskite solar cell.

The instability of the perovskite precursor solution seriously affects the purity of the perovskite films, which is one of the key factors for the low reproducibility for highly efficient devices. Formamidinium‐based perovskite with more suitable spectral absorption range and higher thermal stability has become the mainstream material. However, the side reactions in pure formamidinium lead iodide solution have not been fully revealed. Herein, it is demonstrated that self‐condensation of formamidinium iodide occurs to form the by‐product s‐triazine, and its content increases with the aging time of the solution. It is also discovered that phenylboric acid (PBA) can effectively inhibit the self‐condensation reaction and the content of the s‐triazine is decreased by more than 95% in the solution aging at 60 °C for 7 days. The PBA used as the stabilizer not only enhances purity and decreases defect density of the perovskite films but also strongly enhances the reproducibility for highly efficient perovskite solar cells.

Bromide‐based organo‐metal halide perovskites have shown great potential for use in tandem solar cells, LEDs and photodetectors. Here, we report a new protocol using a one‐step deposition method for producing formamidinium lead bromide (FAPbBr₃) perovskites, which features a solvent engineered intermediate phase to achieve superior films. For the first time, an FABr‐PbBr₂‐DMSO intermediate is identified and single crystals of the same intermediate compound have been synthesized. A systematic investigation of phase evolution in the film formation process reveals that DMSO enables crystallization of the FABr‐PbBr₂‐DMSO intermediate, and thus modulates the crystallization process of FAPbBr₃ perovskite, achieving uniform, smooth films with Volmer–Weber morphology. To prevent hole leakage arising from the larger bandgap of FAPbBr₃ than FAPbI₃, we added an additional layer of Mg‐doped ZnO nanoparticles. As a result, inverted solar cells using these solvent engineered films can achieve power conversion efficiencies (PCEs) of up to 9.06 %, the highest reported efficiency for inverted FAPbBr₃ perovskite devices.

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Efficient organic photovoltaic cells (OPVs) were fabricated by employing two structurally similar Y6 derivations (BTP‐BO‐4F, Y6‐1O) as acceptor and PM6 as donor. The two binary OPVs exhibit high fill factor (FF) (>76%), the complementary short‐circuit‐current density (J _SC) of 25.33 mA/cm² vs. 23.52 mA/cm² and open‐circuit voltage (V _OC) of 0.845 V vs. 0.904 V. The high FFs of binary OPVs indicate the good compatibility of corresponding materials to form efficient charge transport channels. A PCE of 17.59% is obtained from ternary OPVs with 15 wt% Y6‐1O in acceptors, benefiting from the simultaneously improved J _SC of 26.13 mA/cm², V _OC of 0.860 V and FF of 78.26%. The V _OCs of ternary OPVs can be gradually increased along with the incorporation of Y6‐1O, suggesting the preferred formation of an alloyed state between BTP‐BO‐4F and Y6‐1O due to their good compatibility. Meanwhile, the cascaded energy levels of BTP‐BO‐4F and Y6‐1O can form efficient electron transport channels in ternary active layers. The main contribution of Y6‐1O can be summarized as enhancing photon harvesting, optimizing phase separation, and adjusting molecular arrangement. The experimental results may provide new insight on developing efficient ternary OPVs by selecting two well‐compatible acceptors.

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The photovoltaic properties and energy losses of organic solar cells (OSCs) based on non‐fullerene acceptors (NFAs) are highly dependent on their molecular structures and aggregation morphologies. Charge carrier and light management is important to optimize NFA molecules. In this work, four NFAs with different alkyl substituents and end groups named as BTP‐C11‐N2F, BTP‐C9‐N2F, BTP‐C9‐IC4F, and BTP‐C9‐N4F were designed and synthesized by side‐chain shortening, end‐acceptor π‐extension, and fluorination. A favorable morphology was achieved in PM6:BTP‐C9‐N4F‐based OSCs by shortening the alkyl side chain, expanding the conjugation of the end group, and increasing the substitution of fluorine atoms on the end group between these four NFAs. As a result, PM6:BTP‐C9‐N4F‐based OSCs obtained the highest PCE 17.0% with a J _sc of 26.3 mA cm^‐2, a V _oc of 0.85 V, and a FF of 75.7%. In addition, its J _sc and V _oc ×FF product relative to the Shockley–Queisser (S‐Q) limiting values were also increased. Extending the conjugation of the end groups increased the energy levels of NFAs and enabled an E _loss of 0.50 eV with a low non‐radiative recombination loss of as low as 0.20 eV in naphthalene system end group based OSCs. This value is among the lowest energy losses in BTP‐based non‐fullerene OSCs. This work provides a strategy to optimize the molecular structures of NFAs and further improve the properties of Y6 analogues.

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