Extended Carrier Lifetime Research Articles

Alkali Induction Strategy for Artificial Photosynthesis of Hydrogen by TiO2 Heterophase Homojunctions.

The robust separation and utilization of photogenerated electrons-holes (e--h+) are key in accelerating redox reactions. Unlike traditional heterojunction photocatalysts, homojunction features different energy bandgaps with interchangeable compositions that can significantly trigger charge carrier dynamics, but their precise construction remains an ongoing challenge owing to quick lattice-level modulations. Herein, TiO2-based homojunction (HTM-OH) holding dissimilar yet discernible crystalline phases (anatase and rutile) are rationally constructed by a straightforward alkali-induced strategy which enables controllable lattice-transition/orientation. The resulting HTM-OH exhibits speedy separation and well-guided flow of e--h+ over redox sites with extended carrier lifetime, leading to high-rate hydrogen generation (HER, 34.35 mmol g-1 h-1) under simulated sunlight. Moreover, a self-made thin film of HTM-OH indicates a notable scale-up potential under real-time sunlight. This work furnishes a new non-complex homojunction strategy for speeding charge carrier kinetics, credibly extendable to a diverse range of catalysts and applications.

Heteroatomic doping induces charge rearrangement to optimize carrier dynamics in 2D halide perovskites

It is well established that a number of techniques, including applied electric fields, interfacial engineering, structural torsion, and doping, can modulate the geometric and electronic structures of materials, thereby enhancing their photoelectronic properties in two-dimensional (2D) halide perovskites. Among these strategies, doping has proven to be an extremely effective approach; however, the precise mechanisms underlying this effect remain elusive. Herein, we systematically investigated how heteroatom doping, specifically using Sn and Bi dopants, influences the excited-state dynamics of 2D (MA)2PbI4 perovskites using ab initio calculations combined with real-time nonadiabatic molecular dynamics simulations. Our results indicate that the doped systems maintain the octahedral configuration characteristics of the parent material. Notably, doping leads to a significant electron–hole separation in real space, corresponding to an extended carrier lifetime of approximately 140–150 ns, compared to just 2.70 ns for pristine (MA)2PbI4 perovskites. This behavior is primarily governed by a low-frequency vibration mode around ∼200 cm−1. These calculations provide important insights into the potential for atomically modulating carrier behaviors to achieve excellent photovoltaic properties.

Prolonging Charge Carrier Lifetime via Intraband Defect Levels in S-Scheme Heterojunctions for Artificial Photosynthesis.

S-scheme heterostructure photocatalysts, distinguished by unique charge-transfer pathways and exceptional catalytic redox capabilities, have found widespread applications in addressing challenging chemical processes, including the photocatalytic reduction of CO2 with a high reaction barrier. Nevertheless, the influence of intraband defect levels within S-scheme heterojunctions on charge separation, carrier lifetime, and surface catalytic reactions has, for the most part, been overlooked. Herein, we develop a tunable defect-level-assisted strategy to construct an electron reservoir, effectively prolonging the lifetime of charge carriers through the rapid capture and gradual release of photoelectrons within WO3-x/In2S3 S-scheme heterojunctions, as authenticated by femtosecond transient absorption spectroscopy and theoretical simulations. The surface photoredox mechanism, unraveled by Gibbs free energy calculations, demonstrates that oxygen-vacancy-induced defect states in WO3-x/In2S3 heterojunctions unlock the rate-determining H2O oxidation into free oxygen molecules by forming metastable oxygen intermediates, contributing to the facilitation of H2O photooxidation. This distinct role, combined with the extended carrier lifetime, results in boosted CO2 photoreduction with nearly 100 % CO selectivity in the absence of any photosensitizer or scavenger. Our work sheds light on the role of controllable defect levels in governing charge transfer dynamics within S-scheme heterojunctions, thereby inspiring the development of more advanced photocatalysts for artificial photosynthesis.

Development and Performance of ZnO/MoS2 Gas Sensors for NO2 Monitoring and Protection in Library Environments

The presence of harmful oxidizing gases accelerates the oxidation of cellulose fibers in paper, resulting in reduced strength and fading ink. Therefore, the development of highly sensitive NO2 gas sensors for monitoring and protecting books holds significant practical value. In this manuscript, ZnO/MoS2 composites were synthesized using sodium molybdate and thiourea as raw materials through a hydrothermal method. The morphology and microstructure were characterized by X-ray diffraction analysis (XRD), energy dispersive spectroscopy (EDS), field emission scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The ZnO/MoS2 composite exhibited a flower-like structure, with ZnO nanoparticles uniformly attached to the surface of MoS2, demonstrating advantages such as high specific surface area and good uniformity. The gas sensitivity of the ZnO/MoS2 nanocomposites reached its peak at 260 °C, with a sensitivity value around 3.5, which represents an improvement compared to pure ZnO, while also enhancing sensitivity. The resistance of the ZnO/MoS2 gas sensor remained relatively stable in air, exhibiting short response times during transitions between air and NO2 environments while consistently returning to a stable state. In addition to increasing adsorption capacity and improving light utilization efficiency, the formation of hetero-junctions at the ZnO-MoS2 interface creates an internal electric field that effectively promotes the rapid separation of photo-generated charge carriers within ZnO, thereby extending carrier lifetime.

Polarization enhanced carrier performance in GaN/WSSe heterostructures for overall water splitting: A first-principles study

Polarization enhanced carrier performance in GaN/WSSe heterostructures for overall water splitting: A first-principles study

A Spin‐Polarized Electron‐Induced MXene‐KBi0.9Co0.1Fe2O5 Photocatalyst for Enhanced Dye Degradation

In photocatalysts aimed to degrade environmental pollutants, photons are generally used as primary stimuli to generate electron–hole pairs to target the chemical bonds to disintegrate. Recently, electron spin has been reported as an essential degree of freedom to improve the performance of photocatalysts. In this work, spin‐polarized electrons and holes are introduced into a brownmillerite KBi0.9Co0.1Fe2O5 semiconductor and a two‐dimensional (2D) MXene composite system by application of an external magnetic field. The spin polarization properties are monitored by measuring the magnetoresistance effect of the MXene‐KBCFO device, which is related to the carrier transfer efficiency. Remarkably, the photocatalytic performance of MXene‐KBCFO is significantly enhanced by the simultaneous application of an external magnetic field and illumination due to the increased number of spin‐polarized photoexcited carriers caused by the synergy effect of the 2D MXene heterostructure together with the ferromagnetic spin ordering. This results in increased reaction hotspots, effective built‐in electric field, extended carrier lifetime, and reduced charge recombination owing to parallel alignment of electron spin orientation. The results show that the efficiency and stability of photocatalytic dye degradation can be effectively enhanced by manipulating the spin‐polarized electrons in the MXene‐based oxide‐perovskite heterostructure photocatalyst.

Asymmetric main-chain twisted small molecules for efficient polymer solar cells

Asymmetric main-chain twisted small molecules for efficient polymer solar cells

The regular octahedral CdS/K2Nb2O6 core-shell Z-Scheme heterojunction towards enhancing photocatalytic H2 evolution and degradation via synergism of carrier efficiency and light response

The regular octahedral CdS/K2Nb2O6 core-shell Z-Scheme heterojunction towards enhancing photocatalytic H2 evolution and degradation via synergism of carrier efficiency and light response

The 2D porous NiSe/g-C3N4 nanosheets towards enhanced photocatalytic H2 evolution and degradation via synergism of co-catalyst and surface protonation

The 2D porous NiSe/g-C3N4 nanosheets towards enhanced photocatalytic H2 evolution and degradation via synergism of co-catalyst and surface protonation

Effect of doping level on the photoconduction and chemiresistive ethanol gas sensing of lanthanum-doped CuO films

Effect of doping level on the photoconduction and chemiresistive ethanol gas sensing of lanthanum-doped CuO films

Magnetic doping engineering in perovskite microcrystals for boosted photocatalytic CO2 reduction

Magnetic doping engineering in perovskite microcrystals for boosted photocatalytic CO2 reduction

Nanoscale phase management of the 2D/3D heterostructure toward efficient perovskite solar cells

The stabilization of the formamidinium lead iodide (FAPbI3) structure is pivotal for the development of efficient photovoltaic devices. Employing two-dimensional (2D) layers to passivate the three-dimensional (3D) perovskite is essential for maintaining the α-phase of FAPbI3 and enhancing the power conversion efficiency (PCE) of perovskite solar cells (PSCs). However, the role of bulky ligands in the phase management of 2D perovskites, crucial for the stabilization of FAPbI3, has not yet been elucidated. In this study, we synthesized nanoscale 2D perovskite capping crusts with<n>=1 and 2 Ruddlesden-Popper (RP) perovskite layers, respectively, which form a type-II 2D/3D heterostructure. This heterostructure stabilizes the α-phase of FAPbI3, and facilitates ultrafast carrier extraction from the 3D perovskite network to transport contact layer. We introduced tri-fluorinated ligands to mitigate defects caused by the halide vacancies and uncoordinated Pb2+ ions, thereby reducing nonradiative carrier recombination and extending carrier lifetime. The films produced were incorporated into PSCs that not only achieved a PCE of 25.39% but also maintained 95% of their initial efficiency after 2000h of continuous light exposure without encapsulation. These findings underscore the effectiveness of a phase-pure 2D/3D heterostructure-terminated film in inhibiting phase transitions passivating the iodide anion vacancy defects, facilitating the charge carrier extraction, and boosting the performance of optoelectronic devices.

Construction Au/FAPbI3 Schottky Heterojunction towards a High-Speed Electron Transfer Channel for High-Performance Perovskite Quantum Dot Solar Cells.

Formamidinium lead triiodide quantum dot (FAPbI3 QD) exhibits substantial potential in solar cells due to its suitable band gap, extended carrier lifetime, and superior phase stability. However, despite great attempts toward reconfiguring the surface chemical environment of FAPbI3 QDs, achieving the optimal efficiency of charge carrier extraction and transfer in cells remains a challenge. To circumvent this problem, we selectively introduced Au/FAPbI3 Schottky heterojunctions by reducing Au+ to Au0 and subsequently anchoring them on the surface of FAPbI3 QDs, which acts as a light-harvesting layer and establishes high-speed electron transfer channels (Au dot ↔ Au dot). As a result, the champion photoelectric conversion efficiency of solar cells reached 13.68%, a significant improvement over 11.19% of that of FAPbI3-based solar cells. The enhancement is attributed to efficient and directed electron transfer as well as a more aligned energy level arrangement. This work constructed Au/FAPbI3 QD Schottky heterojunctions, providing a viable strategy to enhance QD electron coupling for high-performance optoelectronic applications.

The influence of organic molecular rotation on carrier Dynamics: A case of MAPbI3

The influence of organic molecular rotation on carrier Dynamics: A case of MAPbI3

Boosting optoelectronic performance of (FA)X(MA)1-XPbI3 perovskite solar cells: Via FAI post-treatment engineering

Boosting optoelectronic performance of (FA)X(MA)1-XPbI3 perovskite solar cells: Via FAI post-treatment engineering

Performance Enhancement of Three-Dimensional MAPbI3 Perovskite Solar Cells by Doping Perovskite Films with CsPbX3 Quantum Dots.

Perovskite thin films directly impact solar cell properties, making defect reduction crucial in perovskite solar cell research. In our study, we used perovskite quantum dots in the anti-solvent to act as nucleation centers in MAPbI3 thin films. These centers had lower nucleation barriers than homogeneous nucleation, improving perovskite crystallinity, reducing defects, and extending carrier lifetime. Fine-tuning the energy band also enhanced carrier transport. The most effective results were obtained using CsPb(Br0.5 I0.5)3 perovskite quantum dots. The resulting device, ITO/SnO2/MAPbI3 (300 nm)/spiro-OMeTAD (200 nm)/Ag (100 nm), achieved a 12.88% power conversion efficiency, a 16% increase from the standard element. The modified device maintained approximately 95% of its efficiency over 100 h in a 70% humidity environment.

First-principles study of the effects of Vo on the magnetic and photocatalytic properties of bilayer anatase TiO2(001): C/N/S

First-principles study of the effects of Vo on the magnetic and photocatalytic properties of bilayer anatase TiO2(001): C/N/S

Effect of Sb-Bi alloying on electron-hole recombination time of Cs2AgBiBr6 double perovskite.

The double perovskite material Cs2AgBiBr6, characterized by high stability, low toxicity, and excellent optoelectronic properties, has emerged as a promising alternative to lead-based halide perovskites in photovoltaic applications. However, its photovoltaic conversion efficiency after integration into solar cell devices is less than 3%, significantly lower than that of traditional perovskite solar cells. While alloying methods have been widely applied in the design of photovoltaic materials, their specific role in modulating the lifetime of photo-generated charge carriers in double-perovskite solar cells remains inadequately explored. In this study, through nonadiabatic molecular dynamics (NAMD) simulations, the excited-state dynamics properties of Cs2AgBiBr6 and alloyed Cs2AgSb0.375Bi0.625Br6 samples were compared. The results revealed that the introduction of Sb ions into the double perovskite structure induces lattice deformation upon heating to 300 K, leading to distortion of Bi-Br bonds and enhanced valence band delocalization. Using the decoherence-induced surface hopping method, the capture and recombination processes of charge carriers between different states were simulated. It was suggested that hole lifetime serves as the primary limiting factor for carrier lifetime in Cs2AgBiBr6, and replacing 0.375 proportion of Bi with Sb can decelerate the hole capture rate, extending carrier lifetime by 3-4 times. This study demonstrates that alloying offers a viable approach to optimizing the optoelectronic performance of the Cs2AgBiBr6 perovskite, thereby advancing the application of double perovskite materials in the field of photovoltaics.

Synthesis and characterization of CIS/CISe core–shell structured quantum dots in green systems

I–III–VI2 group compounds, such as CuInSe2 (CISe), and CuInS2 (CIS) quantum dots (QDs), are promising for photovoltaic applications by virtue of their excellent photoelectric properties and low toxicity. Considering that the surface of QDs with smaller sizes tends to have a larger density of defect states, inorganic shell layer modification is beneficial to passivate the surface defects and enhance the optical properties and quantum efficiency of QDs. In this study, a novel core–shell structure was constructed by growing a CISe shell layer with a narrower band gap on the surface of CIS nanocrystals with a wider band gap through a green and simple method. The components and properties of the core–shell QDs were analyzed by different characterization methods (XRD, TEM, EDS, UV–Vis, Raman, and fluorescence spectroscopy). The prepared CIS/CISe core–shell QDs with increased size and good coating effects exhibited high absorbance and extended carrier lifetime while showing quantum effects associated with the CISe shell layer, as well as a promising application in the field of solar cells.

Efficiency Boost in All‐Small‐Molecule Organic Solar Cells: Insights from the Re‐Ordering Kinetics

AbstractAchieving high‐performance in all‐small‐molecule organic solar cells (ASM‐OSCs) significantly relies on precise nanoscale phase separation through domain size manipulation in the active layer. Nonetheless, for ASM‐OSC systems, forging a clear connection between the tuning of domain size and the intricacies of phase separation proves to be a formidable challenge. This study investigates the intricate interplay between domain size adjustment and the creation of optimal phase separation morphology, crucial for ASM‐OSCs’ performance. It is demonstrated that exceptional phase separation in ASM‐OSCs’ active layer is achieved by meticulously controlling the continuity and uniformity of domains via re‐packing process. A series of halogen‐substituted solvents (Fluorobenzene, Chlorobenzene, Bromobenzene, and Iodobenzene) is adopted to tune the re‐packing kinetics, the ASM‐OSCs treated with CB exhibited an impressive 16.2% power conversion efficiency (PCE). The PCE enhancement can be attributed to the gradual crystallization process, promoting a smoothly interconnected and uniformly distributed domain size. This, in turn, leads to a favorable phase separation morphology, enhanced charge transfer, extended carrier lifetime, and consequently, reduced recombination of free charges. The findings emphasize the pivotal role of re‐packing kinetics in achieving optimal phase separation in ASM‐OSCs, offering valuable insights for designing high‐performance ASM‐OSCs fabrication strategies.