Efficient Carrier Transport Research Articles

Flexible Indoor Perovskite Solar Cells by In Situ Bottom-Up Crystallization Modulation and Interfacial Passivation.

A robust perovskite-buried interface is pivotal for achieving high-performance flexible indoor photovoltaics as it significantly influences charge transport and extraction efficiency. Herein, a molecular bridge strategy is introduced utilizing sodium 2-cyanoacetate (SZC) additive at the perovskite-buried interface to simultaneously achieve in situ passivation of interfacial defects and bottom-up crystallization modulation, resulting in high-performance flexible indoor photovoltaic applications. Supported by both theoretical calculations and experimental evidences, it illustrates how SZCs serve as molecular bridges, establishing robust bonds between SnO2 transport layer and perovskite, mitigating oxygen vacancy defects and under-coordinated Pb defects at interface during flexible fabrication. This, in turn, enhances interfacial energy level alignment and facilitates efficient carrier transport. Moreover, this in situ investigation of perovskite crystallization dynamics reveals bottom-up crystallization modulation, extending perovskite growth at the buried interface and influencing subsequent surface recrystallization. This results in larger crystalline grains and improved lattice strain of the perovskite during flexible fabrication. Finally, the optimized flexible solar cells achieve an impressive efficiency exceeding 41% at 1000 lux, with a fill factor as high as 84.32%. The concept of the molecular bridge represents a significant advancement in enhancing the performance of perovskite-based flexible indoor photovoltaics for the upcoming era of Internet of Things (IoT).

Three-dimensional donor-acceptor conjugated porous polymers based on metal-porphyrin and triazine for highly effective photodegradation of organic pollutants in water

Three-dimensional donor-acceptor (D-A) type conjugated porous polymers (CPPs) was designed and synthesized via imine condensation of copper tetraaminoporphyrin (CuTAPP) as donor and 1,3,5-tris-(4-formyl phenyl) triazine (TFPT) as acceptor, named as CuPT-CPP. The CuPT-CPP possesses a high specific surface area (73.7 m2/g) and excellent photophysical properties. The simultaneous introduction of the organometallic molecules and D-A structures in CuPT-CPP could be broadened the visible-light response range (400–800 nm) and facilitated efficient photogenerated carrier separation and transportation. As heterogeneous photocatalysts, CuPT-CPP has excellent photocatalytic performances under visible light irradiation, leading to excellent model pollutant rhodamine B degradation efficiency up to about 100% in 3 h, it has superb stability and reusability during the photocatalytic processes, and CuPT-CPP also exhibited broad substrate adaptability, which could photocatalytic degradation of methylene blue (MB), methyl orange (MO), and tetracycline hydrochloride (TC). This work indicates that three-dimensional D-A type porphyrin- and triazine-based CuPT-CPP has great potential in the practical application of photocatalysis.

Modeling the current-voltage characteristics of Sb2Se3 thin film solar cells through Sah-Noyce-Shockley recombination model

This study investigates the impact of various material parameters, such as film resistivity, the thickness of the absorber layer, uncompensated acceptor density, and carrier lifetime, on the carrier transport and device characteristics of emerging CdS/Sb2Se3 thin-film solar cells. The modeling approach is based on the rigorous Sah-Noyce-Shockley recombination model at the PN-junction, which is based on drift and diffusion collection efficiencies for total current-density calculations. The current-density and voltage have been optimized against the Sb2Se3 thickness and the depletion width at the CdS/Sb2Se3 junction. It has been determined that the lower efficiency of the cell is primarily due to the relatively short electron lifetime and the uncompensated acceptor density, which can widen or narrow the depletion width. The resistivity of the Sb2Se3 film can effectively control the voltage of the cell, however, the carrier lifetime can control this impact even to a higher extent. Therefore, the carrier lifetime and uncompensated acceptor densities are the two interdependent parameters that significantly control the current, voltage, and efficiency of the Sb2Se3 solar cells. This research provides valuable insights for the design and optimization of Sb2Se3 thin-film solar cells shedding light on carrier transport and charge collection mechanism in these emerging materials.

Synergistic photoactivity regulation of Bi2WO6 with highly exposed {0 0 1} facets and oxygen vacancies by base-metal-ion dopant for enhanced reduction of pharmaceutical compounds

Herein, base metal-doped Bi2WO6 nanosheets with a large proportion of exposed {001} facets and oxygen vacancies were prepared and exhibited greatly enhanced photoactivity for removing four kinds of pharmaceutical compounds under visible-light irradiation. Results in this study indicated that both Zn- and Cu-doped nanosheets possessed optimal photocatalytic activity due to their improved light-harvesting ability and transport efficiency of photo-induced carriers, but Cu-doped nanosheets showed better activity than Zn-doped samples attributed to the existence of high-oxidation-state Cu3+ ions. Meanwhile, it was found that the optimal photodegradation condition for the metal ion-doped photocatalysts was neutral pH, 10 mg/L of pollutants concentration and 0.3 g/L of catalyst dosage. The degradation rate of Zn-doped samples was different from Cu-doped ones, while the Zn-doped samples showed almost 100 % degradation rate for hydrocortisone and 87.8 % for atenolol but the Cu-doped ones showed 100 % for hydrocortisone, 99.3 % for bezafibrate, and 82.1 % for carbamazepine. It was found that O2− and 1O2 were the dominant active species for photodegradation and the breakdown products were identified to be hypotoxic generally.

Preparation of chalcogenide perovskite SrHfS3 and luminescent SrHfS3:Eu2+ thin films

As an emerging family of perovskites with S or Se anions, chalcogenide perovskites possess excellent optoelectronic properties that are comparable with halide perovskites, e.g., efficient carrier transport abilities and defect tolerance. Moreover, they are thermodynamically stable and constituted by eco-friendly elements. Among them, chalcogenide perovskite SrHfS3 is found to be a promising light emitting material and is experimentally demonstrated to be a suitable host for the luminescent lanthanide ions like Eu2+. In order to be applied in practical light emitting devices, preparation of the thin film is a critical step. Unfortunately, there are few reports on the growth of SrHfS3 thin films, hindering the knowledge of their thin film properties and applications. In this work, SrHfS3 thin films are prepared by magnetron sputtering from a commercial SrHfO3 target and subsequent sulfurization. Then, Eu2+ doping in SrHfS3 thin films is achieved by co-sputtering from a home-made EuS target. The SrHfS3 thin films exhibit high-quality crystallinity, smooth morphology, and high p-type mobility. With efficient Eu2+ doping strategy, SrHfS3:Eu2+ thin films show intensive red light, which sets foundations for their further application in practical light emitting devices.

Universal growth of perovskite thin monocrystals from high solute flux for sensitive self-driven X-ray detection

Metal-halide perovskite thin monocrystals featuring efficient carrier collection and transport capabilities are well suited for radiation detectors, yet their growth in a generic, well-controlled manner remains challenging. Here, we reveal that mass transfer is one major limiting factor during solution growth of perovskite thin monocrystals. A general approach is developed to overcome synthetic limitation by using a high solute flux system, in which mass diffusion coefficient is improved from 1.7×10–10 to 5.4×10–10 m2 s–1 by suppressing monomer aggregation. The generality of this approach is validated by the synthesis of 29 types of perovskite thin monocrystals at 40–90 °C with the growth velocity up to 27.2 μm min–1. The as-grown perovskite monocrystals deliver a high X-ray sensitivity of 1.74×105 µC Gy−1 cm−2 without applied bias. The findings regarding limited mass transfer and high-flux crystallization are crucial towards advancing the preparation and application of perovskite thin monocrystals.

Enhancing electrical and optical properties in layered NaxCoO2 through sodium non-stoichiometry: Insights into surface band bending and oxygen vacancies

The concentration of sodium ions (Na+) in layered sodium cobaltite (NaxCoO2) is a pivotal determinant influencing its physical and chemical properties. This study focused on NaxCoO2 with varying sodium content (x = 1, 0.9, 0.7, 0.5, 0.3, 0.1) to establish a correlation between the sodium concentration and the substantial modulation of the structural and electrical properties. X-ray diffraction and Raman studies confirmed the formation of hexagonal structured NaxCoO2 prepared by the sol-gel method, while a reduction in Na content increased the percentage of the Co3O4 phase. Notably, as the Na content was lowered, the Raman peak shifted towards a lower wavenumber due to the lattice alignment along the c-axis of the crystal plane. Morphological analysis displayed the growth of distinct plate-like structures, with a thickness ranging from 10 to 15 μm, which gradually decreased on lowering Na content. X-ray photoelectron spectroscopy studies revealed an increase in the relative concentration of Co4+/Co3+ with a decrease in sodium content implying a lattice distortion in CoO6 octahedra which led to the creation of additional oxygen vacancies in Na0.7CoO2 (NCO7). Optical studies highlighted a band bending phenomenon in the NCO7, while photoluminescence studies indicated an increase in emission intensity, suggesting the presence of oxygen vacancies in NCO7. Electrical measurements demonstrated the highest conductivity for NCO7 emphasizing the significance of the optimal lattice distortion, generation of oxygen vacancies, and surface band bending effect for efficient charge carrier transportation. This study highlights the crucial role of the sodium ion content between the CoO2 layers in precise tuning of the structural, electronic structure/distortion, optical, and electrical properties of NaxCoO2. The insights gained particularly in optimizing the optical and electrical properties through sodium non-stoichiometry, may hold significant implications for diverse energy conversion and storage devices, catalysis, and even optoelectronics devices.

High-performance photoelectrochemical (PEC) type self-powered ultraviolet photodetectors (PDs) based on three-dimensional ZnO film/carbon fiber paper

Novel photoelectrochemical ultraviolet detection technologies based on semiconductor/electrolyte heterojunctions have attracted significant attention due to their cost-effective fabrication and self-powered characteristic. In this study, ZnO films were deposited on three-dimensional carbon fiber paper (3D CFP) using a one-step sputtering method, resulting in the preparation of 3D ZnO/CFP composites as photoanodes for photoelectrochemical (PEC) type photodetectors (PDs). The fabricated device demonstrates outstanding photoelectrochemical performance, showcasing a remarkable responsivity of approximately 31.76 mA/W, a detectivity of 3.06 × 1012 jones, and a rapid photoresponse time of 76.51/48.51 ms. Furthermore, the device exhibits exceptional photoresponse stability during cycling tests. The unique structure of 3D CFP, composed of intertwined carbon fiber in three dimensions, offers an enlarged specific surface area and efficient carrier transport pathways for the photoanode in self-powered PEC-PDs. This characteristic facilitates effective electrolyte diffusion throughout the entire film, as well as efficient transport of photo-generated charge carriers, thereby significantly enhancing the overall performance of the PEC-PDs. This study affirms the effectiveness of the synergistic interaction between 3D CFP and ZnO film for advanced UV photodetectors, demonstrating both mass production viability and promise for the future of photoelectrochemical detection technology.

Vapor-transport-deposited Sb2S3 thin-film solar cells: Tailoring photovoltaic properties through deposition temperature

Crystal orientation plays a crucial role in the performance of Sb2S3 thin-film solar cells (TFSCs). Among various deposition techniques, vapor transport deposition (VTD) stands out as a viable technique for producing scalable and uniformly deposited thin films, particularly in the solar industry. This study explores temperature-modulated VTD-Sb2S3 deposition to enable efficient carrier transport in photovoltaic cells. In the VTD process, the deposition temperature is altered between 480 °C and 540 °C. XRD, SEM, EDS, and AFM techniques are employed to obtain the characteristics of the Sb2S3 thin films at varying temperatures and evaluate critical features like crystal structure and orientation, surface morphology, composition, and roughness. The prominent crystal orientation changes from the (hk0) to the (hk1) plane after increasing the deposition temperature from 500 to 520 °C. The (211)- and (221)-planes become more prominent when the deposition temperature exceeds 520 °C. The device with the architecture SLG/Mo/Sb2S3/CdS/i-ZnO/AZO/Al, a substrate-configured TFSC, yields a maximum power conversion efficiency of 0.22% when the VTD-Sb2S3 absorber film is deposited at 520 °C. This study presents a promising approach to producing thin films with a preference for specific crystal orientations. The primary aim is to enhance the efficiency of solar cells that utilize VTD-Sb2S3 absorbers.

Three-Step Process for Efficient Solar Cells with Boron-Doped Passivated Contacts

Crystalline silicon (c-Si) solar cells with passivation stacks consisting of a polycrystalline silicon (poly-Si) layer and a thin interfacial silicon dioxide (SiO2) layer show high conversion efficiencies. Since the poly-Si layer in this structure acts as a carrier transport layer, high doping of the poly-Si layer is crucial for high conductivity and the efficient transport of charge carriers from the bulk to a metal contact. In this respect, conventional furnace-based high-temperature doping methods are limited by the solid solubility of the dopants in silicon. This limitation particularly affects p-type doping using boron. Previously, we showed that laser activation overcomes this limitation by melting the poly-Si layer, resulting in an active concentration beyond the solubility limit after crystallization. High electrically active boron concentrations ensure low contact resistivity at the (contact) metal/semiconductor interface and allow for the maskless patterning of the poly-Si layer by providing an etch-stop layer in an alkaline solution. However, the high doping concentration degrades during long high-temperature annealing steps. Here, we performed a test of the stability of such a high doping concentration under thermal stress. The active boron concentration shows only a minor reduction during SiNx:H deposition at a moderate temperature and a fast-firing step at a high temperature and with a short exposure time. However, for an annealing time tanneal = 30 min and an annealing temperature 600 °C ≤ Tanneal≤ 1000 °C, the high conductivity is significantly reduced, whereas a high passivation quality requires annealing in this range. We resolve this dilemma by introducing a second, healing laser reactivation step, which re-establishes the original high conductivity of the boron-doped poly-Si and does not degrade the passivation. After a thermal annealing temperature Tanneal = 985 °C, the reactivated layers show high sheet conductance (Gsh) with Gsh = 24 mS sq and high passivation quality, with the implied open-circuit voltage (iVOC) reaching iVOC = 715 mV. Therefore, our novel three-step process consisting of laser activation, thermal annealing, and laser reactivation/healing is suitable for fabricating highly efficient solar cells with p++-poly-Si/SiO2 contact passivation layers.

Promoting the carrier mobility of Nb2SiTe4 through cation coordination engineering

Ternary two-dimensional (2D) monoclinic Nb2SiTe4 has garnered significant attention for its potential applications in anisotropic photoelectronics. Yet, its intrinsic indirect bandgap nature and low hole mobility, attributed to the short Nb–Nb dimer configurations, hinder the efficient photogenerated carrier separation and transport. In this Letter, using density functional theory calculations, we demonstrate the interlayer intercalation of Si results in the formation of a metastable orthorhombic Nb2SiTe4 structure devoid of detrimental short Nb–Nb dimers. Notably, this Si intercalation leads to a remarkable reduction of hole effective masses of orthorhombic Nb2SiX4 (X = S, Se, and Te), a crucial factor for achieving high carrier mobility. Taking the orthorhombic Nb2SiTe4 monolayer as an example, the calculated hole mobility (>100 cm2 V−1 s−1) is comparable in magnitude to the respectable hole mobility observed in multiple layers of the monoclinic Nb2SiTe4. To simultaneously enhance electron and hole mobility, we establish a van der Waals junction between the monoclinic and orthorhombic Nb2SiTe4 structures, achieving high and comparable carrier mobilities. The Nb2SiTe4 junction exhibits a nearly direct bandgap of 0.35 eV, rendering it suitable for infrared light harvesting. Furthermore, carriers within the Nb2SiTe4 junction become spatially separated across different layers, resulting in an intrinsic built-in electric field, which is superior for efficient photo-generated charge separation and decreases the potential nonradiative carrier recombination. Our findings highlight the impact of cation coordination engineering on the electronic and optical properties of 2D Nb2SiTe4 and provide a feasible solution to achieve better carrier transport in low-dimensional photovoltaic functionalities.

G-C3N4@CPP/BiOClBr-OV biomimetic fractal heterojunction synergistically enhance carrier dynamics for boosted CO2 photoreduction activity

In recent years, there has been significant interest in generating high-value solar fuels via the photocatalytic reduction of CO2. Nonetheless, its large-scale application is impeded by low energy utilization efficiency and limited photocatalytic activity. This study employed carbonized pomelo peel (CPP), a waste biomass material, to successfully craft a CN@CPP/BOCB-OV ternary heterojunction abundant in N/O vacancy defects through secondary calcination and in-situ growth. The construction of the heterojunction and the emergence of defect-induced donor energy levels create a built-in interface electric field (IEF) and an interfacial electron transmission channel respectively, fortifying the separation and transport of photogenerated electrons. Crucially, following the incorporation of CPP, its distinctive 3D porous and heterojunction bionic flower structures expand the spectral absorption range. Acting as a superior electron acceptor, CPP reinforces the IEF, notably boosting carrier transport efficiency. Simultaneously, it operates as a hub for photothermal synergy and CO2 adsorption activation, achieving multi-site synergistic enhancement of photoreduction CO2 activity. Hence, the CN@CPP/BOCB-OV heterojunction demonstrates a substantial quantitative enhancement in CO2 photoreduction activity. Remarkably, it exhibits the capability to catalyze CO2 reduction even under infrared light excitation, which is of great significance for the cascade utilization of solar energy. Furthermore, employing DFT calculations, we elucidate the electron transfer mechanism at the heterojunction interface and outline potential pathways for photocatalytic CO2 reduction. The combination of waste biomass utilization, heterostructure construction and defect engineering provides a promising strategy for developing efficient heterostructure photocatalysts.

Interfacial electric field optimization and co-catalyst free LaFeO3-based p-p-type homojunction for efficient PEC water splitting

LaFeO3 (LFO), a typical p-type semiconductor, is considered as a promising material for photoelectric conversion because of its flexible composition and structure. However, its severe photogenerated carrier recombination and surface reaction kinetic hysteresis greatly limit its application in photoelectrochemistry (PEC) water splitting. Here, for the first time, a LFO p-p-type homojunction (Cu-LFO/Ni-LFO) formed by Cu-doped LFO and Ni-doped LFO is reported. Experimental investigation and density functional theory (DFT) calculations reveal that Cu and Ni doping forms a built-in electric field directed from Ni-LFO to Cu-LFO, which effectively improves the carrier separation and transport efficiency. The comparable crystal structure at the interface minimizes the photogenerated carrier recombination due to the interface lattice mismatch. In addition, Ni-LFO in contact with the electrolyte served as a co-catalyst like role in this PEC system, improving the kinetic properties of the surface reaction significantly by optimizing the adsorption and desorption of H2O molecules and HER reaction intermediates on the Fe in the active center whilst significantly reducing the energy barrier. As a result, the photocurrent density of the Cu-LFO/Ni-LFO photocathode reaches 5.94 mA cm2, which is 11 times higher than that of Cu-LFO and surpasses all LFO-based photocathodes reported so far. The LFO-based p-p homo-junction synthesized in this work is instructive for improving the carrier separation efficiency and surface reaction kinetics of LFO.

Precise local functionalization of covalent organic framework for efficient carrier separation in photocatalytic H2 evolution

Improving carrier transport rate and suppressing carrier recombination are two huge challenges in the photocatalytic applications of covalent organic frameworks (COFs)-based semiconductors. In this study, we propose a strategy to enhance carrier transport efficiency by regulating the local microenvironment of the electronic characteristics in the acceptors through structural modification. Three different functional group-modified fluorenone-based COFs were successfully synthesized through precise design. The results demonstrate that the photocatalytic hydrogen evolution activities of COFs modified with electron-donating functional groups are significantly higher than that of COFs modified by electron-withdrawing functional groups. Specifically, the photocatalytic hydrogen evolution performance of phenyl-modified FOOPh-COF could reach 228.5 mmol h−1g−1, which is 11.8 times higher than that of Br atom-modified FOOBr-COF (19.3 mmol h−1g−1). Femtosecond time-resolved transient absorption spectroscopy (fs-TAS) results reveal that introducing phenyl groups into the acceptor significantly enhances its inhibitory effect on the carrier recombination. Density functional theory calculations further prove that modifying the acceptor by electron-donating functional groups can achieve the increased electron density in the CO active center. The electrons in the CO region in the phenyl-modified fluorenone structure are more enriched and delocalized, which can enhance the speed of electron migration, shorten the migration distance, and inhibit carrier recombination. After loading Pt, it has the lowest H* adsorption-free energy among three samples. This work clarifies the importance of the functionalization modification of COFs’ acceptors in regulating the local electronic environment and further provides new insights into the structure–activity relationship of fluorenone-based COF-based photocatalysts.

Dramatically Enhanced Light‐Emitting/Detecting Bifunction of CH3NH3PbBr3 Single‐Crystal Thin‐Film via Electrical Doping‐Induced Defects Passivation

AbstractHigh‐performance light‐emitting/detecting bifunctional optoelectronic devices based on halide perovskites are hindered by the less efficient carrier transport and radiative recombination processes. The density of defects (i.e., surface and bulk defects) is the main factor affecting carrier transport, radiation recombination, and determining performance in perovskites. Therefore, techniques to effectively regulate defects are highly needed. Here, a convenient and effective strategy, electrical doping, is proposed to flexibly regulate defect density, resulting in dramatically enhanced light‐emitting (i.e., fluorescence and carrier lifetime) and light‐detecting performance (i.e., hole mobility, photo‐responsivity, and photo‐detectivity) simultaneously. An improved carrier transport model in CH3NH3PbBr3 (MPB) single‐crystal thin‐film (SCTF) is proposed to elucidate the regulation mechanism of defects and carrier transport under electrical doping. These results show that the surface defect density can be effectively reduced by 47.49% under optimal electrical poling intensity (0.168 V µm−1), and photoluminescence intensity and carrier lifetime can be increased by 259% and 89.98%, respectively. Furthermore, planar MPB SCTF photodetector exhibits hole mobility increased by 14.97%, photo‐responsivity increased by 82.78%, and photo‐detectivity increased by 868% at 0.168 V µm−1. Particularly, a record photo‐detectivity of 3.53 × 1013 Jones is achieved under electrical doping. This study provides guidance for flexibly adjusting defect density and optimizing perovskite SCTFs light‐emitting/detecting bifunctional devices.

High‐Performance Organic Phototransistors Based on Single‐Crystalline Microwire Arrays

AbstractHigh‐performance organic phototransistors (OPTs) have attracted considerable attention owing to their high photoresponse and low‐cost solution‐processing manufacturing. To meet the increasing demand for integrated optoelectronic circuits, organic single‐crystalline micro‐/nanowire arrays for OPTs construction are prominently anticipated. However, the manufacturing and patterning of organic single‐crystalline arrays have hit a bottleneck due to the uncontrollable dewetting dynamics. In this work, a capillary‐bridge lithography strategy is proposed to guide ordered nucleation and unidirectional dewetting of microfluid, thus enabling the large‐scale preparation of highly aligned organic single‐crystalline microwire arrays. Taking advantage of efficient carrier transport, a competitive average field‐effect hole mobility (μ) of 6.64 cm2 V−1 s−1 is obtained, and the high‐throughput one‐dimensional (1D) arrays based OPTs also exhibit excellent optoelectrical performance with photosensitivity (P) of 1.36 × 106, responsivity (R) of 3.18 × 104 A W−1, and specific detectivity (D*) of 9.22 × 1014 Jones. This work provides a guide for the designing and patterning of high‐throughput OPTs toward multifunctional integrated optoelectronics.

Strong Dimensional and Structural Dependencies of Hot Carrier Effects in InGaAs Nanowires: Implications for Photovoltaic Solar Cells.

III-V nanowire structures are among the promising material systems with applications in hot carrier solar cells. These nanostructures can meet the requirements for such photovoltaic devices, i.e., the suppression of thermalization loss, an efficient hot carrier transport, and enhanced photoabsorption thanks to their unique one-dimensional (1D) geometry and density-of-states. Here, we investigate the effects of spatial confinement of photogenerated hot carriers in InGaAs-InAlAs core-shell nanowires, which presents an ideal class of hot carrier solar cell materials due to its suitable electronic properties. Using steady-state photoluminescence spectroscopy, our study reveals that by increasing the degree of spatial confinement and Auger recombination, the effects of hot carriers increase, which is in good agreement with theoretical modeling. However, for thin nanowires, the temperature of hot carriers decreases as the effects of crystal disorder increase. This observation is confirmed by probing the extent of the disorder-induced Urbach tail and linked to the presence of a higher density of stacking defects in the limit of thin nanowires. These findings expand our knowledge of hot carrier thermalization in nanowires, which can be applied for designing efficient 1D hot carrier absorbers for advanced-concept photovoltaic solar cells.

Hydrophobic Hydrogen‐Bonded Polymer Network for Efficient and Stable Perovskite/Si Tandem Solar Cells

AbstractThe pursuit of highly efficient and stable wide‐band gap (WBG) perovskite solar cells (PSCs), especially for monolithic perovskite/silicon tandem devices, is a key focus in achieving the commercialization of perovskite photovoltaics. In this study, we initially designed poly(ionic liquid)s (PILs) with varying alkyl chain lengths based on density functional theory calculations. Results pinpoint that PILs with longer alkyl chain lengths tend to exhibit more robust binding energy with the perovskite structure. Then we synthesized the PILs to craft a hydrophobic hydrogen‐bonded polymer network (HHPN) that passivates the WBG perovskite/electron transport layer interface, inhibits ion migration and serves as a barrier layer against water and oxygen ingression. Accordingly, the HHPN effectively curbs nonradiative recombination losses while facilitating efficient carrier transport, resulting in substantially enhanced open‐circuit voltage (Voc) and fill factor. As a result, the optimized single‐junction WBG PSC achieves an impressive efficiency of 23.18 %, with Voc as high as 1.25 V, which is the highest reported for WBG (over 1.67 eV) PSCs. These devices also demonstrate outstanding thermostability and humidity resistance. Notably, this versatile strategy can be extended to textured perovskite/silicon tandem cells, reaching a remarkable efficiency of 28.24 % while maintaining exceptional operational stability.

Hydrophobic Hydrogen-Bonded Polymer Network for Efficient and Stable Perovskite/Si Tandem Solar Cells.

The pursuit of highly efficient and stable wide-band gap (WBG) perovskite solar cells (PSCs), especially for monolithic perovskite/silicon tandem devices, is a key focus in achieving the commercialization of perovskite photovoltaics. In this study, we initially designed poly(ionic liquid)s (PILs) with varying alkyl chain lengths based on density functional theory calculations. Results pinpoint that PILs with longer alkyl chain lengths tend to exhibit more robust binding energy with the perovskite structure. Then we synthesized the PILs to craft a hydrophobic hydrogen-bonded polymer network (HHPN) that passivates the WBG perovskite/electron transport layer interface, inhibits ion migration and serves as a barrier layer against water and oxygen ingression. Accordingly, the HHPN effectively curbs nonradiative recombination losses while facilitating efficient carrier transport, resulting in substantially enhanced open-circuit voltage (Voc ) and fill factor. As a result, the optimized single-junction WBG PSC achieves an impressive efficiency of 23.18 %, with Voc as high as 1.25 V, which is the highest reported for WBG (over 1.67 eV) PSCs. These devices also demonstrate outstanding thermostability and humidity resistance. Notably, this versatile strategy can be extended to textured perovskite/silicon tandem cells, reaching a remarkable efficiency of 28.24 % while maintaining exceptional operational stability.

Boosting carrier separation and transport in CuGaO2 photocathodes by coupled effects of surface polarization and facet-junction

This study investigates the synergistic enhancement of carrier separation and transport in CuGaO2 photocathodes, achieved through the coupled effects of surface polarization and facet-junction engineering. Delafossite CuGaO2 microspheres, which exhibit a flower-like micro-nano hierarchical structure, are synthesized facilely through a one-pot hydrothermal process. These microspheres self-assemble from CuGaO2 nanosheets, driven by electrostatic forces among crystal facets. Morphology and size are systematically modulated by pH values, solvent composition, and reaction temperature. The CuGaO2 nanosheets, serving as fundamental building blocks, manifest notable surface polarization effects that facilitate the efficient transport of photo-generated carriers. The facet-junction formed between intersecting CuGaO2 nanosheets facilitates the collection of photo-generated electrons and holes on both sides of the interface, leading to spatial separation. Consequently, the CuGaO2 microspheres synergistically combine nanoscale surface polarization and microscale facet-junction effects, promoting the effective separation and rapid transport of electron-hole pairs generated under visible-light irradiation. The resulting simple bare photocathode, constructed using CuGaO2 microspheres, demonstrates a photocurrent density of 32 μA/cm2 at zero-bias, with a peak incident photon-to-current efficiency of 12.72 % at a 450 nm wavelength. Further optimization of the CuGaO2 photocathode yields a better photocurrent density of 138 μA/cm2 at 0.33 VRHE. These results underscore the significance of integrating nanoscale surface polarization effects with microscale facet-junction effects to achieve efficient separation and rapid transport of photo-generated carriers in photoelectrochemical cells.