Enhanced Electron Mobility Research Articles

The gas sensing and adsorption properties of XO2 (X = Ti, Zr, Hf) doped C3N towards H2S, SO2, SOF2: A first-principles study

In this paper, XO 2 (X = Ti, Zr, Hf) doped C 3 N nanosheet is firstly proposed to detect SF 6 decomposition products: H 2 S, SO 2 , and SOF 2 . The electronic properties and adsorption mechanisms of XO 2 (X = Ti, Zr, Hf) doped C 3 N nanosheet towards H 2 S, SO 2 , SOF 2 are systematically explored. Metal oxide particles doping effectively modulate the band gap, with the decline of 27.8 %, 22.3 % and 42.6 % in TiO 2 , ZrO 2 and HfO 2 doped systems, furthermore, dopants provide abundant active sites for gas adsorption and enhance electron mobility and electrical conductivity of the pristine C 3 N surface. TiO 2 -C 3 N holds the best adsorption performance among three doping systems, in which the E ads reach up to −1.158 eV, −2.238 eV, −1.574 eV in H 2 S, SO 2 and SOF 2 systems. The τ of H 2 S, SO 2 , SOF 2 escape from TiO 2 -C 3 N surface are 3.7 × 10 7 s, 4.8 × 10 14 s, 6.88 × 10 25 s. Improved adsorption energy of TiO 2 -C 3 N is twice than that of pristine C 3 N nanosheet's. ZrO 2 , HfO 2 -C 3 N have semblable adsorption capacity to target gases. In SO 2 and SOF 2 adsorption of HfO 2 doped systems, SO 2 and SOF 2 obtained the charges of 0.303 e and 0.189 e respectively. The results provide a theoretical basis for further manufacture of industrial hazardous gas sensors and online monitoring of SF 6 insulated equipment. • XO 2 (X=Ti, Zr, Hf) nanoparticle modification is firstly proposed to improve C 3 N’s surface electronic properties. • Transition metal oxides doped C 3 N exhibits ideal adsorption and scavenging properties for H 2 S, SO 2 , and SOF 2 . • The results provide a theoretical basis for further manufacture of industrial hazardous gas sensors and online monitoring of SF 6 insulated equipment.

High performance direct current-generating triboelectric nanogenerators based on tribovoltaic p-n junction with ChCl-passivated CsFAMA perovskite

Herein, we develop direct current-generating triboelectric nanogenerators (DC-TENGs) based on the tribovoltaic p-n junction using n-type perovskite (CsFAMA) and p-type conductive polymer (PEDOT:PSS); CsFAMA based DC-TENG is shown to generate a high DC power output of about 2.1 µA cm−2 (current) and 0.33 V (voltage). We also introduce choline chloride (ChCl) to passivate the defects inside CsFAMA to improve the power-generating performance of DC-TENG by increasing triboelectric charge density, carrier mobility, and built-in potential, which are the key factors that determine device performance. Due to the synergetic effect of reduced defect sites (5.0×1015 cm−3 to 1.0×1015 cm−3), enhanced electron mobilities (1.0×10−2 cm2 V−1 s−1 to 2.3×10−2 cm2 V−1 S−1), and modulated work function, the passivated CsFAMA-based DC-TENG generates an output current density of 11 µA cm−2 and an output voltage of 0.80 V. Our results are expected to contribute to the development of high-performance DC-TENGs by presenting a promising strategy that involves controlling the triboelectric semiconducting interface.

Vitamin Natural Molecule Enabled Highly Efficient and Stable Planar n–p Homojunction Perovskite Solar Cells with Efficiency Exceeding 24.2%

AbstractThe defect passivation and interface energetics‐modification between perovskite and transport layers are significant for the further improvement of efficiency and stability of perovskite solar cells (PSCs). Here, a double‐layer modification engineering strategy is employed by different functionalized natural vitamins into the electron transport layer and perovskite, respectively. Considering the different role of each functional layer in PSCs, the vitamin C (VC) with high conductivity is introduced into SnO2, showing electron mobility enhancement, an interface energy‐levels offsets reduction, and enhanced interfacial charge transfer. Meanwhile, antioxidant vitamin D2 (VD2) with multiple passivating functional groups is introduced into the perovskite bulk to moderately tailor its intrinsic characteristics. The surface energetics of perovskite are changed from n‐type to p‐type, the thickness of the p‐type perovskite is 80 nm, thus the spontaneous n–p homojunction is formed in perovskite caused by VD2, which increases the built‐in electric field and the efficiency of perovskite hole extraction. The synergistic effect of VC and VD2 better heightens the charge extraction efficiency and achieves charge‐carrier transport balance in PSCs. The optimum device achieves a power conversion efficiency of 24.20% and a fill factor of 81.01% with negligible hysteresis. This efficiency is among the best PSCs employing natural molecules reported so far.

Impact of fluorination of central thiophene linking core in thermostable perylene-diimide-based dimeric acceptors on molecular configuration and photovoltaic performance

Fluorination was an easy and effective strategy to adjust the absorption, electronic energy level, molecular configuration and aggregation as well as charge mobility, miscibility, morphology and photovoltaic property. Herein, two perylene-diimide-based non-fullerene dimeric acceptors, called T-(PDI-HD)2 and 2FT-(PDI-HD)2, were obtained via Stille coupling reaction between bistin compounds (TSn and 2FTSn) and monobromide PDI-HDBr. The dramatically reduced twisted angle from 81.80o to 19.78o and strengthened molecular stacking both in chlorobenzene solution and solid film states were found after fluorination, resulting in an elevated thermostability and slightly enhanced electron mobility. Furthermore, fluorination led to the down-shifted ELUMO, worse miscibility and undesired microstructural morphology with oversized aggregation which impeded the exciton dissociation and restricted the photocurrent. As a consequence, the slightly declined VOC, 18.52% down-shifted JSC but 12.38% increased FF were found, leading to a 9.69% decline in PCE from 2.58% to 2.33% after bisfluorinating the central thiophene linking core, which was imputed to the deepened ELUMO, worse light-harvesting capability and undesired morphology as a result of fluorination regardless of the slightly elevated electron mobility. Our results have demonstrated that it was cautious that incorporating fluorine substituents into central linking core by virtue of tuning the twisting degree boosted the photovoltaic property in PDI-based dimeric acceptors.

Regioisomer‐Free Difluoro‐Monochloro Terminal‐based Hexa‐Halogenated Acceptor with Optimized Crystal Packing for Efficient Binary Organic Solar Cells

AbstractHerein, we synthesized new hetero‐halogenated end groups with well‐determined fluorinated and chlorinated substitutions (o‐FCl‐IC and FClF‐IC), and synthesized regioisomer‐free small molecular acceptors (SMAs) Y‐Cl, Y‐FCl, and Y‐FClF with distinct hetero‐halogenated terminals, respectively. The single‐crystal structures and theoretical calculations indicate that Y‐FClF exhibits more compact three‐dimensional network packing and more significant π‐π electronic coupling compared to Y‐FCl. From Y‐Cl to Y‐FCl to Y‐FClF, the neat films exhibit a narrower optical band gap and gradually enhanced electron mobility and crystallinity. The PM6 : Y‐FClF blend film exhibits the strongest crystallinity with preferential face‐on molecular packing, desirable fibrous morphology with suitable phase segregation, and the highest and balanced charge mobilities among three blend films. Overall, the PM6 : Y‐FClF organic solar cells (OSCs) deliver a remarkable efficiency of 17.65 %, outperforming the PM6 : Y‐FCl and PM6 : Y‐Cl, which is the best PCE for reported hetero‐halogens‐based SMAs in binary OSCs. Our results demonstrate that difluoro‐monochloro hetero‐terminal is a superior regio‐regular unit for enhancing the intermolecular crystal packing and photovoltaic performance of hetero‐halogenated SMAs.

Regioisomer-Free Difluoro-Monochloro Terminal-based Hexa-Halogenated Acceptor with Optimized Crystal Packing for Efficient Binary Organic Solar Cells.

Herein, we synthesized new hetero-halogenated end groups with well-determined fluorinated and chlorinated substitutions (o-FCl-IC and FClF-IC), and synthesized regioisomer-free small molecular acceptors (SMAs) Y-Cl, Y-FCl, and Y-FClF with distinct hetero-halogenated terminals, respectively. The single-crystal structures and theoretical calculations indicate that Y-FClF exhibits more compact three-dimensional network packing and more significant π-π electronic coupling compared to Y-FCl. From Y-Cl to Y-FCl to Y-FClF, the neat films exhibit a narrower optical band gap and gradually enhanced electron mobility and crystallinity. The PM6 : Y-FClF blend film exhibits the strongest crystallinity with preferential face-on molecular packing, desirable fibrous morphology with suitable phase segregation, and the highest and balanced charge mobilities among three blend films. Overall, the PM6 : Y-FClF organic solar cells (OSCs) deliver a remarkable efficiency of 17.65 %, outperforming the PM6 : Y-FCl and PM6 : Y-Cl, which is the best PCE for reported hetero-halogens-based SMAs in binary OSCs. Our results demonstrate that difluoro-monochloro hetero-terminal is a superior regio-regular unit for enhancing the intermolecular crystal packing and photovoltaic performance of hetero-halogenated SMAs.

A comparative study on performance of junctionless Bulk SiGe and Si FinFET

In this paper, the n-type and p-type SiGe junctionless bulk FinFET (SiGe JL-FinFET) with a high Ge mole fraction (xF>0.8) was studied for characteristics of a single device and the CMOS logic circuit using 3D numerical simulation. A comparison study between SiGe JL-FinFET and Si JL-FinFET under 1×1019 to 5×1019 doping concentrations. The SiGe JL-FinFET exhibits a 28% and 9% enhancement of hole and electron mobility, thus the saturation current, transconductance, intrinsic gain, and intrinsic delay are improved up to 38%, 26%, 45% and 27% in the SiGe-based device as compared to the Si-based device. Due to the higher mobility and lower gate capacitance of SiGe JL-FinFET, the rise time, fall time, propagation delay, and maximum operating frequency of the CMOS inverter are also improved up to 34%, 13%, 9%, and 20%, respectively, compared to their Si-based counterparts. This SiGe junctionless device has a simple fabrication process and improvements in analog and digital performance at the sub-5 nm technology node, making this device a promising architecture for high-performance CMOS logic applications.

Hydrogen-iodide bonding between glycine and perovskite greatly improve moisture stability for binary PSCs

In recent years, the maximum power conversion efficiency (PCE) of perovskite solar cells (PSCs) has exceeded 25%. However, stability, especially under high relative humidity, has become a great obstacle for commercialization of perovskite devices due to its intrinsic defects. Interface modification is an effective method to improve the performance of PSCs for it could validly restrain defects and prevent decomposition of perovskite. In this paper, interface properties have been greatly improved by glycine (GLY) doped SnO 2 electron transport layer (ETL) in planar binary PSCs. SnO 2 -GLY ETL leads to improved band alignment, reduced charge recombination and enhanced electron mobility. XPS and NMR results demonstrate that the ammonia group in GLY combined with perovskite through hydrogen-iodide bonding, which greatly improves the moisture stability of the devices. The best PCE of the perovskite solar cell increased from 19.08% to 21.18%, and GLY modified devices can maintain 88% of its initial PCE after 7 days under 60 ± 5% relative humidity (RH) in ambient condition without any encapsulation. While, thermal stability test results indicating that hydrogen bonding is just a little helpful for improving stability at high temperature. This work indicates that forming hydrogen bonding between perovskite and ETL is an effective way to enhance moisture stability for commercialization of PSCs. • Interface properties between SnO 2 ETL and PSCs are improved by glycine (GLY), leading to enhanced PCE from 19.11% to 21.18%. • The amino group in GLY is bound to perovskite by hydrogen iodide bond, which greatly improves water stability of the device. • Long-term and thermal stability of the devices have also been improved.

Low-temperature characteristics and gate leakage mechanisms of LPCVD-SiNx/AlGaN/GaN MIS-HEMTs

In this paper, we systematically investigated the static properties and gate current mechanism of low-pressure chemical vapor deposition-SiNx/AlGaN/GaN metal–insulator–semiconductor-high-electronmobility-transistor (MIS-HEMTs) at cryogenic temperature range from 10 K to 300 K. It is found that the threshold voltage of the device shows a positive shift due to the decreased carrier concentration at low temperature, and both the maximum transconductance and ON-resistance are improved at the low temperatures because of the enhanced electron mobility. Under very low electric field, the gate leakage exhibits ohmic conduction. With increasing forward gate bias, the dominant gate leakage mechanism at temperature below150 K gradually transits into trap-assisted tunneling, participating with a deep trap energy level of 0.73 eV in the SiNx dielectric, to Fowler–Nordheim (FN) tunneling. In contrast, the dominant gate leakage mechanism at temperature above 150 K transits from Poole–Frenkel emission, showing a low trap barrier height of 56 meV in the SiNx dielectric, to Fowler–FN tunneling with increasing forward gate bias. Under high reverse gate bias, carrier-limited gate current becomes the dominated gate leakage mechanism.

Promoting the Efficiency and Stability of Nonfullerene Organic Photovoltaics by Incorporating Open-Cage [60]Fullerenes in the Nonfullerene Nanocrystallites.

The device efficiency of PM6:Y6-based nonfullerene organic solar cells is fast advanced recently. To maintain organic solar cells (OSCs) with high power conversion efficiency over 16% in long-term operation, however, remains a challenge. Here, a novel non-volatile additive, an open-cage [60]fullerene (8OC60Me), is incorporated into PM6:Y6-based OSCs for high-performance with high durability. With optimized addition of 1.0 wt % 8OC60Me, the PCE value of PM6:Y6/8OC60Me OSCs can be promoted to 16.5% from 15.0%. Most strikingly, such a high PCE performance can maintain nearly 100% for over 500 h at room temperature; at an elevated operation temperature of 80 °C, the PCE can be stabilized above 15.0% after 45 h of operation. Grazing incidence small- and wide- angle X-ray scattering studies reveal improved orientation and crystallinity of Y6 in a fractal-like network structure of PM6 in PM6:Y6/8OC60Me films under in situ annealing, parallel to the enhanced electron mobility. Analysis of charge distributions lines up possible van der Waals interaction between the thienyl/carbonyl moiety of 8OC60Me and difluorophenyl-based FIC-end groups of Y6. This result is of great contrast to those devices with the best-selling PC61BM as the additives─8OC60Me might be of interest to be incorporated into future Y6-based OSCs for concomitantly improved PCE and excellent stability.

Binary Blend All-Polymer Solar Cells with a Record Efficiency of 17.41% Enabled by Programmed Fluorination Both on Donor and Acceptor Blocks.

Despite remarkable breakthrough made by virtue of “polymerized small‐molecule acceptor (PSMA)” strategy recently, the limited selection pool of high‐performance polymer acceptors and long‐standing challenge in morphology control impede their further developments. Herein, three PSMAs of PYDT‐2F, PYDT‐3F, and PYDT‐4F are developed by introducing different fluorine atoms on the end groups and/or bithiophene spacers to fine‐tune their optoelectronic properties for high‐performance PSMAs. The PSMAs exhibit narrow bandgap and energy levels that match well with PM6 donor. The fluorination promotes the crystallization of the polymer chain for enhanced electron mobility, which is further improved by following n‐doping with benzyl viologen additive. Moreover, the miscibility is also improved by introducing more fluorine atoms, which promotes the intermixing with PM6 donor. Among them, PYDT‐3F exhibits well‐balanced high crystallinity and miscibility with PM6 donor; thus, the layer‐by‐layer processed PM6/PYDT‐3F film obtains an optimal nanofibril morphology with submicron length and ≈23 nm width of fibrils, facilitating the charge separation and transport. The resulting PM6/PYDT‐3F devices realizes a record high power conversion efficiency (PCE) of 17.41% and fill factor of 77.01%, higher than the PM6/PYDT‐2F (PCE = 16.25%) and PM6/PYDT‐4F (PCE = 16.77%) devices.

Interface modulated electron mobility enhancement in core–shell nanowires

The transport properties of core–shell nanowires (CSNWs) under interface modulation and confinement are investigated based on the atomic-bond-relaxation (ABR) correlation mechanism and Fermi’s golden rule. An analytical expression for the relationship between carrier mobility and interface mismatch strain is derived and the influence of size, shell thickness and alloyed layer on effective mass, band structures, and deformation potential constant are studied. It is found that interface modulation can not only reduce the lattice mismatch to optimize the band alignment, but also participate in the carrier transport for enhancing mobility. Moreover, the underlying mechanism regarding the interface shape dependence of transport properties in CSNWs is clarified. The great enhancement of electron mobility suggests that the interface modulation may become a potential pathway to improving the performance of nanoelectronic devices.

Isomerization of Asymmetric Ladder‐Type Heteroheptacene‐Based Small‐Molecule Acceptors Improving Molecular Packing: Efficient Nonfullerene Organic Solar Cells with Excellent Fill Factors

AbstractMoving one subunit of the central core to the other side in a small‐molecule acceptor (SMA) is an effective approach to achieve the goal of isomerization, which has proven viable to enhance photovoltaic performance. Herein, two isomeric SMAs of ThPy5 and ThPy6 are developed by changing the position of the thiophene unit of the dithieno[3,2‐b:2′,3′‐d]pyrrol in IDTP‐4F. The effect of altering the thiophene position on morphological characteristics, macroscopic factors, and device performance is thoroughly investigated among these three isomeric SMAs. Compared to ThPy5, IDTP‐4F and ThPy6 show planar molecular structures and better molecular orientation. Moreover, tighter π–π stacking as well as enhanced electron mobility is observed in ThPy6 relative to IDTP‐4F. PM6:ThPy6‐based organic solar cells (OSCs) achieve the maximum efficiency of 16.11%, along with an excellent fill factor (FF) of 0.789, which are among the best results for A‐D‐A‐type SMA‐based OSCs. The high FF ascribes to the improved molecular packing and charge collection/extraction efficacy and the reduced charge recombination. The structure–morphology–performance relationship drawn from this work can offer better guidance for designing the molecular structure, especially the central cores of SMAs.

Realizing Interfacial Electron/Hole Redistribution and Superhydrophilic Surface through Building Heterostructural 2nm Co0.85 Se-NiSe Nanograins for Efficient Overall Water Splittings.

Electrochemical overall water splitting using renewable energy input is highly desirable for large-scale green hydrogen generation, but it is still challenged due to the lack of low-cost, durable, and highly efficient electrocatalysts. Herein, 1D nanowires composed of numerous 2nm Co0.85 Se-NiSe nanograin heterojunctions as efficient precious metal-free bifunctional electrocatalyst are reported for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline solution with the merits of high activity, durability, and low cost. The abundant microinterface among the ultrafine nanograins and the presence of lattice distortion around nanograin interface is found to create a superhydrophilic surface of the electrocatalyst, which significantly facilitate the fast diffusion of electrolytes and the release of the formed H2 and O2 from the catalyst surface. Furthermore, synergic effect between Co0.85 Se and NiSe grain on adjusting the electronic structure is revealed, which enhances electron mobility for fast electron transport during the HER/OER process. Owing to these merits, the rationally designed Co0.85 Se-NiSe heterostructures display efficient overall water splitting behavior with a low voltage of 1.54V at 10mAcm-2 and remarkable long-term durability for the investigated period of 50h.

Boosting thermoelectric performance of BayCo4Sb12 by interlinking large-aspect-ratio silver nanowires at the triple junction of grain boundaries

Decoupling electrons and phonons transport has been a major challenge for enhancing thermoelectric (TE) performance. Incorporation of guest nano-inclusions into host phases has been proven effective for enhanced phonon scattering but induces additional electron scattering, resulting in limited effect in the improvement of TE performance. Herein, one-dimensional high-conducting silver nanowires (AgNWs) with a large aspect ratio have been uniformly incorporated into Ba0.2Co4Sb12 matrix. The AgNWs become Y shaped at the triple junctions of the grain boundaries, which create more hetero-interfaces for tuning the TE properties. The semi-coherent hetero-interfaces minimized the electron scattering, and the large-aspect-ratio AgNWs facilitate their interlinks, thus remarkably promoting the carrier mobility due to the reduction of boundary potential barrier. Meanwhile, the AgNWs could form nano-meso-micro-scale defects on random cross-sectional planes due to random penetration angles, bringing in full-wavelength phonon scattering. In a combined effect, a peak zT of 1.24 was achieved, enhanced by ∼43%. The corresponding TE module exhibited a high conversion efficiency of ∼8%, among the highest ever reported. This work demonstrated an effective strategy for enhancing TE performance by incorporating one-dimensional large aspect ratio conducting nanowires into the host phases with simultaneous reduction of thermal conductivity and enhancement of electron mobility.

Synthesis and characterization of n-type semiconducting graft copolymers with polystyrene side chains

In this study, we synthesized and evaluated graft copolymers with polystyrene (PSt) as side chains on poly {[N,N´-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′ -bithiophene)} [P(NDI2OD-T2)], which is a typical n-type semiconducting polymer applied to in organic photovoltaics due to its intense optical absorption for the visible light, and high electron affinity. A well-controlled structure was confirmed by 1H-NMR analysis. It was found that enhanced electron mobilities in graft copolymer films were observed compared with the homopolymer. In order to clarify the role of PSt chains and the origins of the enhanced mobility, UV–vis absorption, electrochemical, morphological and thermal characteristics, and crystalline nature were investigated. As the results, it is suggested that the improved mobilities were attributed to the enhanced growth of π–π stacks, and increased crystallinity induced by PSt graft chains.

Ab Initio Study of Two-Dimensional Cross-Shaped Non-Fullerene Acceptors for Efficient Organic Solar Cells.

In the present work, five novel non-fullerene acceptor molecules are represented to explore the significance of organic solar cells (OSCs). The electro-optical properties of the designed A–D–A-type molecules rely on the central core donor moiety associated with different halogen families such as fluorine, chlorine, and bromine atoms and acyl, nitrile, and nitro groups as acceptor moieties. Among these, M1 exhibits the maximum absorption (λmax) at 728 nm in a chloroform solvent as M1 has nitro and nitrile groups in the terminal acceptor, which is responsible for the red shift in the absorption coefficient as compared to R (716 nm). M1 also shows the lowest value of the energy band gap (2.07 eV) with uniform binding energy in the range of 0.50 eV for all the molecules. The transition density matrix results reveal that easy dissociation of the exciton is possible in M1. The highest value of the dipole moment (4.6 D) indicates the significance of M4 and M2 in OSCs as it reduces the chance of charge recombination. The low value of λe is given by our designed molecules concerning reference molecules, indicating their enhanced electron mobility. Thus, these molecules can serve as the most economically efficient material. Hence, all newly designed non-fullerene acceptors provide an overview for further development in the performance of OSCs.

Giant Modulation of the Electron Mobility in Semiconductor Bi2O2Se via Incipient Ferroelectric Phase Transition.

High-mobility layered semiconductors have the potential to enable the next-generation electronics and computing. This paper demonstrates that the ultrahigh electron mobility observed in the layered semiconductor Bi2O2Se originates from an incipient ferroelectric transition that endows the material with a robust protection against mobility degradation by Coulomb scattering. Based on first-principles calculations of electron-phonon interaction and ionized impurity scattering, it is shown that the electron mobility of Bi2O2Se can reach 104 to 106 cm2 V-1 s-1 over a wide range of realistic doping concentrations. Furthermore, a small elastic strain of 1.7% can drive the material toward a unique interlayer ferroelectric transition, resulting in a large increase in the dielectric permittivity and a giant enhancement of the low-temperature electron mobility by more than an order of magnitude. These results establish a new route to realize high-mobility layered semiconductors via phase and dielectric engineering.

Enhancement of optical phonons limited electron mobility in an AlGaN step-shaped quantum well

Achieving high conductivity in n-type AlGaN of deep ultraviolet light-emitting diodes is still a challenge nowadays. In the Lei–Ting equilibrium equation method framework, a four-layer quantum well with n-Al0.7Ga0.3N barriers and an Al0.55Ga0.45N/AlxGa1−xN bi-component well could obtain a much higher electron mobility μT than that in a single-component quantum well over a relatively broad Al content range 0.56 < x < 0.68. While the built-in electric field induces strong confinement, pushing the electron to the interface, the optical phonon mode at this interface could be component-modulated to disappear due to the ternary mixed crystal effect. A significant enhancement of electron mobility can be achieved by avoiding the scattering from optical phonons at the interface where the electron gathers. The optical phonon limited μT could reach 7966 cm2/V s at x = 0.58, which is almost five times of 1518 cm2/V s in the case of x = 0.55 and ten times of 822 cm2/V s for x = 0.70. Such a step-shaped quantum well with high electron mobility could be an alternate or insert layer to the high Al content n-layer to alleviate the current crowding.

Two‐Dimensional Polycyclic Photovoltaic Molecule with Low Trap Density for High‐Performance Photocatalytic Hydrogen Evolution

Typical organic semiconductors show a high trap density of states (1016 -1018 cm-3 ), providing a large number of centers for charge-carrier recombination, thus hindering the development of photocatalytic hydrogen evolution. Here, we design and synthesize a two-dimensional polycyclic photovoltaic material, named as TPP, to reduce the trap density to as low as 2.3×1015 cm-3 , which is 1-3 orders of magnitude lower than those of typical organic semiconductors. Moreover, TPP exhibits a broad and strong absorption, ordered molecular packing with a large crystalline coherence length and enhanced electron mobility. Then, the bulk heterojunction nanoparticles (BHJ-NPs) based on a blend of polymer donor (PM6) and TPP exhibit an average hydrogen evolution rate (HER) of 64.31 mmol h-1 g-1 under AM1.5G sunlight (100 mW cm-2 ), and 72.75 mmol h-1 g-1 under 330-1100 nm illumination (198 mW cm-2 ) higher than that of the control NPs based on typical PM6 : Y6 (62.67 mmol h-1 g-1 ).