Narrow Band Gap Research Articles

Scrutinizing the untapped potential of emerging ABSe3 (A = Ca, Ba; B = Zr, Hf) chalcogenide perovskites solar cells

ABS3chalcogenide perovskites (CPs) are emerging as promising alternatives to lead halide perovskites due to their unique properties. However, their bandgap exceeds the Shockley-Queisser limit. By substituting S with Se, the bandgap is significantly reduced, shifting it from the visible into the near-infrared region. Hence, we have investigated the potential of Se-based absorbers with device structure FTO/TiO2/ABSe3 (A = Ca, Ba; B = Zr, Hf)/NiO/Au using SCAPS-1D. We analyzed the critical parameters impacting each layer of the solar cell. Notably, we achieved an enhanced light absorption (~ 26.5%) at an optimal absorber thickness (500 nm), intensifying carrier generation. Additionally, we observed an increase in VOC (1.03 V) due to improved quasi-Fermi level splitting and a reduction in energy loss (0.45 V) across all solar cells with an optimal absorber carrier concentration (1016 cm−3). Overall, the optimization resulted in improvements in PCE by the difference of 20.14%, 20.44%, 14.33%, and 14.56% for CaZrSe3, BaZrSe3, CaHfSe3, and BaHfSe3 solar cells, respectively. The maximum PCE of over 30% was attained for both CaZrSe3and BaZrSe3 solar cells, attributed to their narrow bandgap, enhanced light absorption (53.60%), high JSC (29 mA/cm2), and elevated generation rate of 1.19 × 1022 cm−2s−1. Thus, these significant outcomes highlight the potential of these absorbers for fabricating high-efficiency CP solar cells.

Reducing Nonradiative Recombination in Halide Perovskites through Appropriate Band Gaps and Heavy Atomic Masses.

Halide perovskite optoelectronic devices achieve high energy conversion efficiencies. However, their efficiency decreases significantly with an increase in temperature. This decline is likely caused by changes in nonradiative recombination and electron-phonon coupling, which remain underexplored. When the perovskite lattice temperature increases, anharmonicity induces energy level fluctuation and band gap narrowing by modulating electron-phonon interactions. As lattice vibrations intensify, high-frequency phonons progressively dominate the carrier dynamic processes in halide perovskites, thereby strengthening the coupling between the electronic subsystem and high-frequency phonons. The increased overlap of electron wave functions strengthens non-adiabatic coupling, thereby accelerating the nonradiative recombination process. On the basis of these findings, we propose the introduction of appropriate band gap materials and heavy atoms at the B-site and X-site to modulate electron-phonon coupling, thereby mitigating nonradiative recombination and enhancing halide perovskite solar cell performance.

Laminated Two-Terminal All-Perovskite Tandem Solar Cells with Transparent Conductive Adhesives.

Established sequential deposition of multilayer two-terminal (2T) all-perovskite tandem solar cells possesses challenges for fabrication and limits the choice of materials and device architecture. In response, this work represents a lamination process based on a transparent and conductive adhesive that interconnects the wide-bandgap (WBG) perovskite top solar cell and the narrow-bandgap (NBG) perovskite bottom solar cell in a monolithic 2T all-perovskite tandem solar cell. The transparent conductive adhesive (TCA) layer combines Ag-coated poly(methyl methacrylate) microspheres with an optical adhesive. The TCA is employed as a recombination junction, achieving self-encapsulation with high transparency and good conductivity. A high vertical electrical conductivity is realized by optimizing the distribution of microspheres using a novel solidification strategy that employs UV curing and drying at 85 °C at low pressure. In addition, uniform and dense bilayer hole transport layers are realized by vapor-phase evaporation, which facilitates the application of the TCA and achieves pinhole-free buried interfaces in both the WBG perovskite top solar cell and the NBG perovskite bottom solar cell. Using these two strategies, losses in fill factor (FF) and open-circuit voltage (VOC) of the 2T all-perovskite tandem solar cell are reduced, achieving a respectable power conversion efficiency up to 18.2% for the lamination of the all-perovskite tandem solar cell. The laminated tandem solar cell retains ∼93% of initial efficiency after exposure in ambient air (30-70 RH% and 20-35 °C) for ∼30 days.

Narrow bandgap 1D g-C3N4/3D-Bi2MoO6 self-assembled heterojunction structure with enhanced photocatalytic performance for removal of MB or Cr (VI)

Narrow bandgap 1D g-C3N4/3D-Bi2MoO6 self-assembled heterojunction structure with enhanced photocatalytic performance for removal of MB or Cr (VI)

Integration of p-Type PdPc and n-Type SnZnO into Hybrid Nanofibers Using Simple Chemical Route for Enhancement of Schottky Diode Efficiency

Palladium phthalocyanine (PdPc) and palladium phthalocyanine integrated with tin–zinc oxide (PdPc:SnZnO) were prepared using a simple chemical approach, and their structural and morphological properties were identified using X-ray diffraction, energy dispersive X-ray analysis, scanning electron microscopy, and transmission electron microscopy techniques. The PdPc:SnZnO nanohybrid revealed a polycrystalline structure combining n-type metal oxide SnZnO nanoparticles with p-type organic PdPc molecules. The surface morphology exhibited wrinkled nanofibers decorated with tiny spheres and had a large aspect ratio. The thin film revealed significant optical absorption within the ultraviolet and visible spectra, with narrow band gaps measured at 1.52 eV and 2.60 eV. The electronic characteristics of Al/n-Si/PdPc/Ag and Al/n-Si/PdPc:SnZnO/Ag Schottky diodes were investigated using the current–voltage dependence in both the dark conditions and under illumination. The photodiodes displayed non-ideal behavior with an ideality factor greater than unity. The hybrid diode showed considerably high rectification ratio of 899, quite a low potential barrier, substantial specific photodetectivity, and high enough quantum efficiency, found to be influenced by dopant atoms and the unique topological architecture of the nanohybrid. The capacitance/conductance–voltage dependence measurements revealed the influence of alternative current signals on trapped centers at the interface state, leading to an increase in charge carrier density.

Optical Simulation and Modulation of Semitransparent Organic Solar Cells with Dual Ultrathin Ag Film Transparent Electrodes

The advancement of semitransparent organic solar cells utilizing narrow bandgap donor and acceptor materials has progressed rapidly in recent years. These semitransparent devices exhibit high absorption in the near‐infrared range and high transmission in the visible region, offering broad application potential. This research suggests employing dual ultrathin metal films as transparent electrodes to fabricate semitransparent photovoltaic devices. The investigation focuses on the spectral simulation and modulation of the transparent electrode structure, film thickness, optical coupling layer, and 1D photonic crystal utilizing the optical transfer matrix method. The primary goal of the integrated optical effects is to enhance the light absorption in the active layer while maintaining device visible transparency. Simulation results indicate the feasibility of a device structure consisting of Nb2O5/Ag/Nb2O5/PM6:BTP‐eC9:L8‐BO/MoO3/Ag/ZnSe/Na3AlF6/ZnSe, achieving an expected short‐circuit current density () of 17.10 mA cm−2, an average visible transmittance (AVT) of 50.40%, and a light utilization efficiency (LUE) of 5.49%. The incorporation of three nonperiodic dielectric layers shows the potential to further increase , AVT, and LUE to 17.40 mA cm−2, 51.49%, and 5.71%, respectively. This study introduces a novel device structure that optimizes active layer absorption and visible transmittance, aiming to advance semitransparent photovoltaic devices.

Rational Design of Quinoidal Conjugated Polymers for Photothermal Antibacterial Therapy.

The increasing prevalence of antibiotic resistance, driven by the overuse and misuse of conventional antibiotics, has become a critical public health concern. Photothermal antibacterial therapy (PTAT) utilizes heat generated by photothermal agents under light exposure to inhibit bacterial growth without inducing resistance, attracting more and more attention. Quinoid conjugated polymers, especially para-azaquinodimethane (AQM) polymer, are a class of organic semiconductors known for efficient π-electron delocalization, near-infrared absorption, and narrow bandgap, showing great potential in the application of photothermal reagents. However, current AQM polymers face challenges related to their solubility, photostability, and biocompability. In this study, tetraglycol is introduced onto the AQM core for improving the drawbacks of the resulting polymers. Two AQM polymers with different electron donor (thiophene and 2,2'-bithiophene) are synthesized and evaluated for their various properties. PAQMT exhibited superior performance, including higher extinction coefficients, improved light absorption, and greater stability under repeated NIR irradiation. PAQMT is further developed into nanoparticles via encapsulation, resulting in excellent colloidal stability, effective bacterial inhibition under 808nm NIR light. This work provides new strategy in improving the solubility, photostability, and photothermal properties of AQM polymers, offers opportunities for promoting the application of quinoidal conjugated polymers in PTAT.

Two-Dimensional Layered Germanium Iodide Perovskite Ferroelectric Semiconductors.

The discovery of ferroelectricity in two-dimensional (2D) semiconductors has opened a new and exciting chapter in next-generation electronics and spintronics due to their lattice-dimensionality-induced unique behaviors and fascinating functionalities brought by spontaneous polarization. The emerging layered halide perovskites with 2D lattices provide a great platform for generating reduced symmetry and low-dimensional ferroelectricity. Herein, inspired by the approach of reduced lattice dimensionality, a series of 2D layered germanium iodide perovskite ferroelectric semiconductors A2CsGe2I7 [where A = PA (propylammonium), BA (butylammonium) and AA (amylammonium)] was firstly developed, which demonstrates remarkable semiconducting features including narrow direct bandgap (~1.8 eV) and high conductivity over 32.23 nS/cm. Emphatically, these layered germanium iodide perovskites manifest large in-plane ferroelectric polarization over ~10.0 μC/cm2, mainly attributed to the large off-centering ion displacement induced by stereo-active lone-pairs of Ge2+ . More specifically, in contrast to three-dimensional ferroelectric CsGeI3, the representative 2D layered BA2CsGe2I7 manifests a superior polarization-sensitive bulk photovoltaic effect with a polarization ratio of 1.68 and high short circuit current density up to 81.25 μA/cm2, superior to those of reported layered halide perovskite ferroelectrics. This work provides an exciting pathway for the development of 2D ferroelectric semiconductorsand sheds light on their further applications in photoelectronic fields.

Multiple Exciton Generation on Doped Wide-Band Semiconductor Photoanode with Hierarchical Quantum Structure.

The multiple exciton generation (MEG) effect, which produces multiple photo-generated charge carriers from a single high-energy photon absorption by a semiconductor with a narrow bandgap, has the potential to revolutionize photovoltaic, photoelectric detection, and other technologies. Here, this work finds that the surface carbon-modified wide-bandgap photoanode with hierarchical quantum structure can drive a photoelectrochemical reaction with a quantum efficiency exceeding 145% by the first time. More studies reveal that the presence of the MEG effect in the MEG-CdS photoanode is attributed to the formation of high-quality surface C-modified CdS quantum nanosheets on CdS bulk film by in situ, this hierarchical quantum structure leads to quantum confinement effects that increase effective Coulomb interaction for driving MEG and decrease competition for thermal exciton cooling. The acceptor level introduced by carbon reduces the MEG threshold (approximately twice the energy level difference) and collaborates with the built-in electric field of the C-CdS/bulk-CdS homojunction to enable the effective generation and separation of photo-generated charge carriers. The internal quantum efficiency of the MEG-CdS photoanode reaches up to a recording value of 145%, providing a novel perspective on the contribution of surface-modified wide-band semiconductors and their quantum effects in the application of MEG.

Unlocking the Photoluminescence Potential of Tabebuia Rosea Dyes: A Novel Natural Source of Broadband Visible Spectral Fluorescence for OLED Technologies.

This investigation delves into the extraction of polyphenols from the flowers of Tabebuia rosea using a basic maceration approach with acetone, ethanol, and methanol as solvents. The spectroscopic analysis of the dye obtained confirms the existence of functional groups in the polyphenol extract. The study also explores optoelectronic, fluorescence, and photometric characteristics associated with polyphenols. Micro-destructive surface techniques, such as XPS led to the acquisition of detailed information on the extracted polyphenol. The XPS analysis verified the chemical composition of the dyes, revealing that C1s, O1s, and N1s peaks are the main signals for the extracted polyphenols. Additionally, the LC-MS analysis reveals the extract contains significant amounts of active compounds in the polyphenols class, which share a common polyphenol structure. FT-IR spectroscopy confirms the presence of functional groups in the polyphenol dye extract. The optical properties showed a narrow direct bandgap (Eg= 3.08eV), indirect bandgap (Eg=2.77eV), high refractive index (n = 1.52), dielectric constant (ε = 8.982), and high optical conductivity (σ = 3.54 x103 S/m) for the polyphenols extracted in methanol solvent. Polyphenols are characterized by high quantum yield, substantial lifetime, and notable Stoke's shift. In addition, these polyphenol dyes demonstrate strong broadband visible spectra and cover a spectrum from blue to green (x = 0.32 → 0.33 and y = 0.33 → 0.38) in different solvent conditions. Such attributes make them advantageous for use in Organic-LEDs and other optoelectronic technologies, underscoring their significant potential in these domains. In addition, polyphenols are important in removing DPPH-free radicals from the environment, contributing to the production of highly antioxidant green materials.

Photocatalytic degradation performance of a chitosan/ZnO-Fe3O4 nanocomposite over cationic and anionic dyes under visible-light irradiation.

The sonochemical synthesis of a chitosan-ZnO/Fe3O4 nanocomposite yielded a highly porous structure and large surface area for enhancing the photocatalytic degradation of cationic (rhodamine B, RhB) and anionic (methyl orange, MO) dyes in aqueous solution. Chitosan-ZnO/Fe3O4 demonstrated a significant enhancement in photodegradation efficiency 99.49% for MO (C 0 = 5.32 mg L-1, t = 150 min) and 90.73% for RhB (C 0 = 5.03 mg L-1, t = 150 min) under visible light due to its narrow bandgap of 2.84 eV. The photocatalytic performance was investigated by varying the pH, dye concentration, reaction time, and catalyst dose. The photocatalytic reaction obeyed the Langmuir-Hinshelwood kinetic model owing to a high rate constant of 0.031 (min-1) and 0.013 (min-1) for the degradation of MO and RhB, respectively. The photocatalytic activity of the chitosan-ZnO/Fe3O4 nanocomposite lost 18.37% (MO degradation) and 11.08% (RhB degradation) of its performance after the first four cycles. The presented results highlight the degradation efficiency of the chitosan-ZnO/Fe3O4 nanocomposite under visible light irradiation with reusable and magnetically retrievable abilities.

Synthesis of Nonplanar Push-Pull Chromophores with Various Heterocyclic Moieties via [2 + 2] Cycloaddition-Retroelectrocyclization Reaction.

A series of 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) derivatives with various heterocyclic moieties, including pyridine, carbazole, indole, and benzothiadiazole, was newly synthesized through a [2 + 2] cycloaddition-retroelectrocyclization reaction. Symmetric electron-rich 1,3-butadiynes with end-capped heterocyclic substituents were reacted with tetracyanoethylene (TCNE), yielding the target TCBD products in 60-80% yields under ambient or mild heating conditions. The thermal stability and optical and electrochemical properties of both 1,3-butadiyne precursors and the corresponding TCBD derivatives were investigated by using thermogravimetric analysis (TGA), UV-vis spectroscopy, and cyclic voltammetry (CV). The TCBD derivatives featured narrow bandgaps due to the intramolecular charge transfer interactions of push-pull chromophores. In addition, the optimized structures and frontier molecular orbitals with their energy levels were determined by density functional theory (DFT) calculations.

Enhancement of Photocatalytic Activity in BiFeO3 Nanoparticles through Electrical Polarization

This study investigates the enhancement of photocatalytic properties in BiFeO3 nanoparticles through an additional electrical polarization (poling) pretreatment process. BiFeO3, a promising multiferroic material with a narrow bandgap of ≈2. 12 eV, is well‐suited forvisible light‐driven photocatalysis. However, its photocatalytic efficiency isoften limited by insufficient photogenerated charge availability. To address this, a poling process was employed to align the ferroelectric domains within BiFeO3 nanoparticles, improving charge separation and enhancing photocatalytic activity. The findings reveal that the poling process preserves the intrinsic bandgap of BiFeO3, maintaining its visible light absorption capability. Steady‐state photoluminescence spectroscopy shows a marked increase in the intensity in poling‐treated samples, indicating enhanced charge carrier generation. Photo degradation experiments using Indigo dye as a model pollutant demonstrate that poling‐treated BiFeO3 achieves a remarkable photodegradation efficiency of 99%, compared to 56% for untreated BiFeO3. Additionally, the poling‐treated BiFeO3 retains 65% of its initial efficiency after four cycles, highlighting its durability for sustained environmental applications. This study underscores the effectiveness of poling in enhancing the photocatalytic performance of BiFeO3 nanoparticles, providing valuable insights into the development of efficient photocatalysts via domain engineering for environmental purification technologies.

Synergistic Improvement of Narrow Bandgap PbS Quantum Dot Solar Cells through Surface Ligand Engineering, Near-Infrared Spectral Matching, and Enhanced Electrode Transparency.

The tunability of the energy bandgap in the near-infrared (NIR) range uniquely positions colloidal lead sulfide (PbS) quantum dots (QDs) as a versatile material to enhance the performance of existing perovskite and silicon solar cells in tandem architectures. The desired narrow bandgap (NBG) PbS QDs exhibit polar (111) and nonpolar (100) terminal facets, making effective surface passivation through ligand engineering highly challenging. Despite recent breakthroughs in surface ligand engineering, NBG PbS QDs suffer from uncontrolled agglomeration in solid films, leading to increased energy disorder and trap formation. The limited NIR transparency of commonly used indium-doped tin oxide (ITO) electrodes and inadequate NIR radiation from commercially available solar simulators further compromise the true performance of NBG PbS QDs in solar cells. Here, we employ a hybrid ligand strategy based on inorganic cadmium halide and organic thiol molecules, leading to the partial substitution of surface Pb atoms with Cd heteroatoms. This hybrid ligand strategy substantially reduces undesired QD fusion in solid films, improving the photophysical and electronic properties. By modulating the thickness of the ITO layer and managing refraction loss through a ZnO layer coating, we improved NIR transparency to above 80%. We combine an NIR light source with a solar simulator to achieve near-ideal spectral matching for a broader range with standard AM1.5G illumination. Enhancements in surface passivation of QDs, improvements in NIR transparency of electrodes, and a spectral matched light source setup help us achieve solar cell power conversion efficiencies of 12.4%, 4.48%, and 1.37% under AM 1.5G, perovskite filter, and silicon filter illuminations, respectively. A record open-circuit voltage (Voc) of 0.54 V and short-circuit current density (Jsc) of 38.5 mA/cm2 are achieved under AM 1.5G illumination. We attribute these advancements in photovoltaic parameters to the reduction in Urbach tail states and intermediate trap density originating from superior surface passivation of QDs.

Band Tailoring Enabled Perovskite Devices for X-Ray to Near-Infrared Photodetection.

Perovskite semiconductors have shown significant promise for photodetection due to their low effective carrier masses and long carrier lifetimes. However, achieving balanced detection across a broad spectrum-from X-rays to infrared-within a single perovskite photodetector presents challenges. These challenges stem from conflicting requirements for different wavelength ranges, such as the narrow bandgap needed for infrared detection and the low dark current necessary for X-ray sensitivity. To address this, this study have designed a type-II FAPbI3 perovskite-based heterojunction featuring a large energy band offset utilizing narrow bandgap tellurium (Te) semiconductor. This innovative design broadens the detection range into the infrared while simultaneously reducing dark current noise. As-designed device allows for the detection of near infrared band, achieving a detectivity of 6.8 × 109 Jones at 1550 nm. The low dark current enables X-ray sensitivity of up to 1885.1 µC Gy⁻¹ cm⁻2. First-principles calculations confirm the type-II band structure alignment of the heterojunction, and a self-driven response behavior is realized. Moreover, this study have developed a scalable 40 × 1 sensor array, demonstrating the potential for wide-spectrum imaging applications. This work is expected to advance the application of perovskite-based wide-spectrum devices.

Construction of Cu2MoS4/ZnO Heterostructures and Mechanism of Photocatalytic Hydrogen Production.

Constructing wide and narrow band gap heterogeneous semiconductors is a method to improve the activity of photocatalysts. In this paper, CMS/ZnO heterojunctions were prepared by solvothermal loading of ZnO particles on the surface of Cu2MoS4 nanosheets. The photocatalytic H2 precipitation rate is about 545 μmol·g-1·h-1, which is 6.8 times that of Cu2MoS4 and 3 times that of ZnO without any cocatalyst. After etching modification of CMS, the photocatalytic hydrogen production efficiency of the ECMS/ZnO heterojunction is further improved. Its hydrogen production efficiency reaches about 1115 μmol·g-1·h-1, which is 9 times that of ECMS and 6 times that of ZnO. The reasons are mainly attributed to the following two factors: (1) the formation of the ECMS/ZnO type-II-type heterojunction facilitates the effective separation of photogenerated electrons and holes; (2) the band structure of Cu2MoS4 was optimized by etching modification, which made the ECMS/ZnO heterojunction have lower interfacial charge transfer resistance and improved the photocatalytic hydrogen production activity of the heterojunction.

Alkoxy Modification of the Terminal Group in Nonfullerene Acceptors to Achieve Efficient Ternary Organic Solar Cells With a High Open‐Circuit Voltage

AbstractY‐series nonfullerene acceptors (NFAs) usually bear halogenated end groups to achieve narrow bandgaps and tunable molecules crystallinity; however, it results in small open‐circuit voltage (Voc) of 0.8–0.9 V. Here, three Y‐series NFAs BTP‐eC9‐G51, BTP‐eC9‐G52, and BTP‐eC9‐G53 are synthesized by introducing both an electron‐withdrawing fluoro group and electron‐donating alkoxy group to commonly used 2‐(3‐oxo‐2,3‐dihydroinden1‐ylidene)‐malononitrile (IC) terminal groups. These compounds demonstrate a high Voc larger than 0.9 V when employed as acceptors in organic solar cells (0.91 V for BTP‐eC9‐G51 and 0.95 V for the others). The effect of alkoxy chain length of the molecules on the photoelectric properties is systematically studied. The results show that the dipole moments and aggregation behaviors of these molecules changes obviously with the increase of alkoxy chain length. The active layer based on BTP‐eC9‐G51 shows suitable phase separation structure and good charge transport. Devices based on BTP‐eC9‐G51 achieve a device efficiency of 16.65%, higher than those of BTP‐eC9‐G52 and BTP‐eC9‐G53 based devices (14.33% and 13.24%, respectively). Furthermore, BTP‐eC9‐G51 is introduced into D18:L8‐BO devices as a third component, which improves the Jsc and Voc, reduces the nonradiation energy loss, and the device efficiency is increased to 19.03% with a high Voc of 0.92 V.

Ternary Organic Solar Cells Based on S, N‐Heteroacene Non‐Fullerene Acceptors with Unfused Architecture A‐D‐D‐A‐Type

In this study, two distinct unfused non‐fullerene acceptors (NFAs) are synthesized by arranging them in an A‐D‐D‐A pattern, both containing same D‐D central S, N‐heteroacene but different terminal acceptors, namely BTA (NFA‐2) and IC (NFA‐3). Their optical and electrochemical properties are investigated. Both NFA‐2 and NFA‐3 display the high lowest unoccupied molecular orbital energy level, leading to an increased open circuit voltage in the organic solar cells. PBDB‐T is chosen as polymer donor, showing spectral absorption that complements both NFAs. The optimized organic solar cells, based on PBDB‐T:NFA‐2 and PBDB‐T:NFA‐3 attained power conversion efficiency of 9.24% and 13.50%, respectively. Since the absorption characteristics of NFA‐2 and NFA‐3 are complementary, a small amount of NFA‐2 is added into PBDB‐T:NFA‐3 binary blend, the ternary organic solar cells attained a power conversion efficiency of 15.24%. The rise in power conversion efficiency is linked to the higher values of both short circuit current and fill factor. The increased short circuit current value in ternary organic solar cells is linked to the efficient use of excitons produced in NFA‐2 by transferring energy from NFA‐2 to NFA‐3 and effective exciton dissociation, faster charge extraction, decreased bimolecular and trap‐assisted recombination. The enhanced value of FF is also linked to the processes mentioned earlier. This investigation shows that it is advantageous to use separate non‐fused NFAs with absorption spectra that complement each other and have overlapped PL spectra of a medium bandgap acceptor along with the absorption spectra of a narrow bandgap NFA in ternary organic solar cells.

Enhancing the Built-in Electric Field in Oxygen Vacancies-Enriched I-Doped Bi3O4Cl for Visible Light-Driven Photocatalytic Oxidation.

In semiconductor catalysts, rational doping of nonmetallic elements holds significant scientific and technological importance for enhancing photocatalytic performance. Here, using a one-step hydrothermal technique, we synthesized iodine-doped Bi3O4Cl composite and evaluated the impact of iodine doping on its photocatalytic capability for organic dye degradation under visible light irradiation. In this study, we demonstrate that the introduction of iodide ions not only provides an ideal built-in electric field (BIEF) for Bi3O4Cl but also induces the generation of additional oxygen vacancies (OVs). The significantly enhanced BIEF, along with the collaborative effect of the OVs-induced narrow bandgap in Bi3O4Cl, effectively promotes the separation and transfer efficiency of photogenerated charges while suppressing recombination. Under this driving force, photogenerated electrons transfer to the surface OVs, facilitating the activation of surface oxygen, thereby forming highly active superoxide radicals (•O2). Simultaneously, oxygen vacancy engineering can reduce the reaction energy barrier, thereby facilitating the formation of singlet oxygen (1O2), which contributes significantly to photocatalytic processes. The results indicate that under visible light, the prepared iodine-doped Bi3O4Cl exhibits a 6.5-fold increase in the degradation rate constant for rhodamine B and demonstrates enhanced photocatalytic activity toward methyl orange and methylene blue. This study not only provides strong references for optimizing structural design to enhance photocatalytic performance but also offers profound insights into the synergistic effects of BIEF and OVs on charge transfer mechanisms in photocatalytic systems.

Simultaneous passivation of surface and bulk defects in all‐perovskite tandem solar cells using bifunctional lithium salts

AbstractAll‐perovskite tandem solar cells have garnered considerable attention because of their potential to outperform single‐junction cells. However, charge recombination losses within narrow‐bandgap (NBG) perovskite subcells hamper the advancement of this technology. Herein, we introduce a lithium salt, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), for modifying NBG perovskites. Interestingly, LiTFSI bifunctionally passivates the surface and bulk of NBG by dissociating into Li+ and TFSI− ions. We found that TFSI− passivates halide vacancies on the perovskite surface, reducing nonradiative recombination, while Li+ acts as an interstitial n‐type dopant, mitigating the defects of NBG perovskites and potentially suppressing halide migration. Furthermore, the underlying mechanism of LiTFSI passivation was investigated through the density functional theory calculations. Accordingly, LiTFSI facilitates charge extraction and extends the charge carrier lifetime, resulting in an NBG device with power conversion efficiency (PCE) of 22.04% (certified PCE of 21.42%) and an exceptional fill factor of 81.92%. This enables the fabrication of all‐perovskite tandem solar cells with PCEs of 27.47% and 26.27% for aperture areas of 0.0935 and 1.02 cm2, respectively.image