Carrier Transport Pathway Research Articles

Transport dynamics of photo-induced carriers in GaN quantum well infrared photodetectors influenced by triangular potentials

The intrinsic spontaneous and piezoelectric polarizations of GaN lead to the formation of triangular wells and barriers, resulting in the manifestation of chaotic transport models in GaN quantum well intersubband transition (ISBT) infrared detectors and giving rise to various adverse effects. The APSYS software was utilized to construct a novel GaN quantum well ISBT infrared detector in this study. By endeavoring to modify the quantum well structure, our objective was to precisely adjust the energy level of the first excited state (E1) to align with the apex of the triangular barrier. The objective is to reduce the transport barrier for photo-induced carriers and simultaneously investigate the mechanisms through which the triangular potentials influence the transport modes of ISBT infrared detectors. The construction of a GaN/AlGaN quantum well device reveals that the inclusion of 10 periods of 1.7/2.0 nm GaN/Al0.8Ga0.2N in the device structure results in an ISBT absorption wavelength of approximately 1550 nm. In comparison to the deep well structure featuring 2.0/2.0 nm GaN/AlN, the polarization field strengths of both wells and barriers in the quantum well region exhibit a reduction of 23% and 36%, respectively, while the depth of the well decreases by 0.35 eV. The E1 energy level penetrates the region of a triangular barrier, resulting in an approximate 18.5-fold enhancement of the absorption coefficient. By employing innovative transient spectroscopy techniques in conjunction with AC impedance spectroscopy, we have conducted an in-depth analysis of the transport dynamics of photo-induced carriers. The results reveal that the time constant for carrier transport within the E1 energy level, situated in the region of a triangular barrier, amounts to 318.9 ps, thereby indicating a remarkable enhancement in the overall transport process. Furthermore, based on impedance spectroscopy data, this work has successfully derived equivalent circuit models for various quantum well structures and distinct carrier transport pathways, thus providing valuable theoretical insights to optimize photo-induced carrier transportation.

Enhancing charge carrier dynamics with an N-type polymer guest for printable ternary organic solar modules

The ternary strategy offers a promising route to enhance the power conversion efficiencies (PCEs) of organic solar cells (OSCs). In this contribution, we focus on the state-of-the-art binary system PM6:L8-BO and reveal how the n-type polymer guest (PYIT) in the PM6:L8-BO:PYIT ternary system enhances carrier dynamics, thereby improving both efficiency and scalability for large-area printable OSC modules. These benefits are primarily attributed to two key factors: (i) the excellent miscibility of the PYIT guest with the host materials, coupled with the chain-dominant structure and high crystallinity nature of the PYIT polymer, which creates additional pathways for carrier transport and charge transfer; (ii) the incorporation of PYIT, which limits the excessive aggregation of L8-BO, improves molecular packing, and reduces film defects, thereby enhancing exciton dynamics. These optimizations lead to an increase in PCEs from 17.58% in the binary system to 18.59% in the ternary OSC, with improvements across all photovoltaic parameters. More importantly, the PM6:L8-BO:PYIT ternary system exhibits excellent compatibility with large-area printing processes, as demonstrated by a doctor blading OSC module achieving 15.57% PCE over an area of 11.7 cm2. This work highlights the potential of the ternary methodology in tuning the physical properties of OSCs while enhancing both performance and scalability.

Reactive Force-Field Molecular Dynamics Study for Analysis of Silicon Nanocrystal Formation Process in Silicon Oxide Film

Recently, Tunnel Oxide Passivated Contact (TOPCon) solar cells using ultra-thin silicon oxide (SiO x ) films as passivation films have attracted attention due to the high conversion efficiency of 25.7% [1]. Generally, thick SiO x films exhibit excellent passivation performance and lead to long-term reliability of the solar cells[2]. However, in TOPCon solar cells, the thickness of the passivation film is limited to 1~2 nm due to the high electrical resistance of the SiO x film. Therefore, a new SiO x film (named NATURE contact) with improved conductivity through silicon nanocrystals (Si NCs) have been developed by Tsubata et al. [3]. The left figure shows the structure of NATURE contact. It consists of three SiO x layers with different oxygen concentrations. The Si NCs formed in the thin Si-rich layer in the center functions as a carrier transport pathway. The passivation film with the NATURE contact has shown a good passivation performance and conductivity even for relatively thick SiO x films. Since the effects of multidimensional process parameters during NATURE contact formation have been neither elucidated nor optimized, there is significant room for performance improvement in NATURE contact. Therefore, it is of crucial importance to understand the atomic level growth process of Si NCs during formation of NATURE contact and its impact of the oxygen concentration and temperature.We employed Reactive force-field molecular dynamics (ReaxFF MD) method, which reproduces chemical reactions using a bond order-dependent concept. The method has been used in studies such as Si deposition simulations [4]. The periodic boundary conditions were applied to the simulation box for all directions in the size of 65 Å × 40 Å × 45 Å. Crystalline silicon was placed throughout the simulation box and the atoms of the simulated Si NC section were fixed in the center of the box. Crystals other than the fixed portion are then made amorphous using the Melt-Quench method. Finally, the fixation was released to allow the entire box to react. Crystallinity was evaluated by the average radius calculated from the number of atoms constituting the crystal. It is noted that the average radius is evaluated up to 25 Å due to the size of the simulation box. Annealing was performed in the following three processes: pre-moistening, amorphization, and crystal growth. We varied the temperature of crystal growth at 1500 - 2500 K and the oxygen concentration at 0 - 5 %. We investigated the effects of temperature and oxygen concentration on the growth of Si NCs in a-SiO x .The right figure shows the transition of the mean radius of the Si NCs at different temperatures. As a result, when the temperature was varied, a peak in the size of crystal growth was observed at 2250 K, and the crystals disappeared at 2500 K. The trend of maximum crystal growth at a certain temperature and the qualitative agreement were experimentally confirmed [5]. This result suggests that the change in the size of Si NCs occurred because the kinetic energy of Si atoms is larger than the energy barrier required from a-Si to c-Si. The initially placed Si NC of 269 atoms was appropriately shaped or grown. This is consistent with the nucleation theory[6]. When the oxygen concentration was increased, no crystal growth was observed. Experiments have shown that increasing oxygen concentration tends to suppress crystallization [3]. This result suggests that the change in the size of Si NCs was caused by the interdiffusion of silicon and oxygen.

Boosting carrier transport via functionalized short-chain conjugated ligands enables efficient green perovskite quantum dot light-emitting diodes

Lead-halide perovskite quantum dots (QDs) have garnered significant attention in the field of light-emitting diodes (LEDs), owing to their near-unity photoluminescence quantum yield (PLQY) and superb color purity. However, the presence of insulating long-chain organic ligands and imbalanced carrier transport within QLED devices pose significant challenges to performance enhancement. To address these issues, a series of short-chain conjugated ligands based on 3-phenyl-2-propen-1-amine bromide (PPABr), tailored with diverse substituents, are developed. Through comprehensive theoretical calculations and experimental validation, it demonstrated that these ligands effectively modulate carrier transport in perovskite QDs, facilitating more efficient carrier transport pathways and enhanced conductivity through their delocalized electron cloud distributions along the entire molecular backbone. Consequently, QLEDs based on 4-CH3 PPABr QDs achieved an impressive external quantum efficiency (EQE) of 18.67 %, while a peak EQE of 23.88 % can be achieved by integrating a lens-based structure for optimized light extraction. This work offers a novel perspective for mitigating carrier transport imbalance in optoelectronic devices, thereby advancing the development of high-performance QLEDs.

High-loading homogeneous crosslinking enabled ultra-stable vertical organic electrochemical transistors for implantable neural interfaces

Organic electrochemical transistors (OECTs) with high transconductance, low driving voltage, and biocompatibility have emerged as dominant bioelectronics technologies. However, a significant challenge remains in achieving stable signal recording over extended durations, due to the restricted thermal and cycling stability. Here, by introducing a small molecular with double-end functionalized trifluoromethyl-substituted diazirine (DtFDA) as the crosslinker in the organic mixed ionic-electronic conductors (OMIECs), both p- and n-type vertical OECT (vOECT) achieves excellent thermal adaptability (> 100 °C), excepti°nal cycling stability (> 200,000 cycles), fast ion transporting capability (transient time < 1 ms), along with ultrahigh maximum transconductance (gm) (> 0.34 S). The findings reveal that highly loaded crosslinkers (OMIEC:DtFDA = 1:1 in mass) triggered by ultraviolet can facilitate the formation of stable and homogeneous transistor channel, which holds lower crystallinity, wider d spacing, and face-on dominated packing, thereby leading to enhanced ion hydration/injection and decent carrier transport pathways. Moreover, in vivo brain recordings with stable signals were accessed from the developed ultraflexible vOECT even after a four-week interval, and the tissue biocompatibility was also validated by chronic epicortical implantation. This work signifies new possibilities for high-performance vOECTs with high fidelity signals recording under complicated operation environments, enabling broader implications for robust bioelectronics.

Revolutionizing dye-sensitized solar cells with nanomaterials for enhanced photoelectric performance

Dye-sensitized solar cells have emerged as a promising alternative to conventional solar cells due to their cost-effectiveness and ease of fabrication. In recent years, the integration of nanomaterials into dye-sensitized solar cells has garnered substantial attention, offering new avenues to enhance their photoelectric performance. This review comprehensively examines the role of nanomaterials in elevating the efficiency and functionality of dye-sensitized solar cells. The fundamental principles of dye-sensitized solar cells are introduced, emphasizing the intricate interplay between crucial components that enable light absorption, charge separation, and electron transport. Nanomaterials play important roles across the entire spectrum of photoelectric conversion of dye-sensitized solar cells, e.g., constructing light-trapping architectures, creating interlayer transmission bridges, and facilitating charge carrier transport pathways, thus offering cost-effective alternatives to precious metals. Furthermore, this review concludes the central role of nanomaterials in shaping the landscape of flexible optoelectronic materials, highlighting their paramount importance in this area. The extensive scientific insights presented herein not only showcase the cutting-edge achievements in solar energy conversion efficiency but also serve as a comprehensive guide for the proper selection of nanomaterials. Finally, this work outlines the forthcoming challenges and offers insights into promising research avenues based on a comprehensive examination of various scholarly pursuits. Unlike other reviews that focus on the analyses of structures or components, this review concentrates on the impact of nanomaterials on the overall photoelectric performance of dye-sensitized solar cells. By fostering cross-disciplinary collaboration and advancing relevant research, dye-sensitized solar cells hold promise as a significant contributor to the global transition toward clean and renewable energy sources.

Effective N‐Doping of Non‐Fullerene Acceptor via Sequential Deposition Enables High‐Efficiency Organic Solar Cells

AbstractCharge transport in the active layer, which can be effectively modulated by molecular doping of organic semiconductors, significantly affects the photovoltaic performance of organic solar cells (OSCs). However, it is difficult to control the dopant distribution in the bulk heterojunction (BHJ) films, which hinders efficient doping in OSCs. Herein, an effective n‐doping strategy is developed via sequential deposition (SD) of D18 donor and doped acceptor. The favorable vertical component distribution in SD films helps to optimize carrier transport pathways. The SD method confines the n‐dopant N‐DMBI to the acceptor layer, allowing positive effects of molecular doping. Consequently, the doped SD device exhibits superior charge transport with suppressed charge recombination, lower trap density, and enhanced charge extraction compared to the undoped one, resulting in a high power conversion efficiency of 19.55% for D18/L8‐BO binary OSCs. In addition, the doping does not affect the thermal stability of the devices, with the doped SD device retaining over 90% of its initial efficiency after 1200 h of heating at 80 °C. The universality of the SD doping method is also verified in other non‐fullerene acceptor systems. These results demonstrate the great potential of SD doping strategy for building high‐performance OSCs with enhanced charge transport.

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.

Atomically precise metal nanoclusters combine with MXene towards solar CO2 conversion.

Atomically precise metal nanoclusters (NCs) have been deemed a new generation of photosensitizers for light harvesting on account of their quantum confinement effect, peculiar atom-stacking mode, and enriched catalytic active sites. Nonetheless, to date, precise charge modulation over metal NCs has still been challenging considering their ultra-short carrier lifetime and poor stability. In this work, we conceptually demonstrate the integration of metal NCs with MXene in transition metal chalcogenide (TMC) photosystems via a progressive, exquisite, and elegant interface design to trigger tunable, precise and high-efficiency charge motion over metal NCs, stimulating a directional carrier transport pathway. In this customized ternary heterostructured photosystem, metal NCs function as light-harvesting antennas, MXene serves as a terminal electron reservoir, and the TMC substrate provides suitable energy level alignment for retracting photocarriers of metal NCs, giving rise to a spatial cascade charge transport route and markedly boosting charge separation efficiency. The interface configuration and energy level alignment engineering synergistically contribute to the considerably enhanced visible-light-driven photocatalytic CO2-to-CO reduction performance of the metal NCs/TMCs/MXene heterostructure. The intermediate active species during the photocatalytic CO2 reduction are unambiguously determined, based on which the photocatalytic mechanism is elucidated. Our work will provide an inspiring idea to bridge the gap between atomically precise metal NCs and MXene in terms of controllable charge migration for solar-to-fuel conversion.

Surface-induced film structure for enhanced carrier transport of the conjugated/insulating polymer blends at a low semiconductor content

In this work, a donor-acceptor copolymer poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)- alt(3,3‴-di(2-decyltetradecyl)-2,2'; 5′,2''; 5″,2‴-quaterthiophene-5,5‴-diyl)] (PffBT4T-2DT) has been blended with the insulating polystyrene (PS) to fabricate the field-effect transistors (FETs). The blend films deposited on the SiO2 dielectric by the octadecyltrichlorosilane (OTS) modification, exhibit the FET mobility 1–2 orders of magnitude higher than those on the unmodified dielectric, as well as a 10–100 folds enhancement of mobility with decreasing the PffBT4T-2DT ratios at the concentration range of 30 wt. %-5 wt. %. Detailed microstructural characterizations reveal that the OTS modification induces the change of phase-separation structure in the blend film, in which more aggregates of the PffBT4T-2DT are enriched near the semiconductor/dielectric interface. Furthermore, the OTS modification of substrate and the addition of PS facilitate the conversion from face-on to edge-on stacking orientation so that the edge-on packing structure dominates in the films with a semiconductor content of 5–10 wt. %. Based on these results, we propose that the remarkably elevated mobility at low PffBT4T-2DT contents is attributed to the enhanced edge-on arrangement of PffBT4T-2DT as well as the favorable interconnect network of chain aggregates formed at the semiconductor/dielectric interface for efficient carrier transport pathway.

Photocatalytic fuel cell based on integrated silicon nanowire arrays/zinc oxide heterojunction anode for simultaneous wastewater treatment and electricity production

Photocatalytic fuel cells (PFCs) convert organic waste into electricity, thereby providing a potential solution for remediating environmental pollution and solving energy crises. Most PFCs for energy generation applications use powder photocatalysts, which have poor mechanical stability, high internal resistance, and may detach from the substrate during reactions, leading to unstable performance. Integrated photoelectrodes can overcome the drawbacks of powder catalysts. In this study, an integrated photoanode was prepared based on a silicon nanowire arrays/zinc oxide (Si NWs/ZnO) heterojunction by combining metal-assisted chemical etching (MACE) and hydrothermal methods. The resulting photoanode was used to assemble a PFC for simultaneous electricity generation and Rhodamine (RhB) dye wastewater degradation. This PFC showed excellent cell performance under irradiation, with a short-circuit current density of 0.183 Am−2, an open-circuit voltage (OCV) of 0.72 V, and a maximum power density of 0.87 W m−2. It could also be used continuously 20 times while degrading > 90% of RhB. This performance was ascribed to the three-dimensional (3D) structure and large surface area of Si NWs, as well as the matched band structure of ZnO, which facilitated the efficient separation and transport of photogenerated carriers in Si NWs/ZnO. The integrated structure also shortened the carrier transport pathways and suppressed carrier recombination. This research provides a foundation for the development of efficient, stable, low-cost, small-scale PFCs.

Transparent p–n Junction in Cu2O/ZnS/ZnO Core–Shell Nanoarrays via In Situ Sulfuration for Enhanced Photovoltaic Stability

A Cu2O/ZnS/ZnO core–shell orderly nanoarray transparent p–n junction was prepared using a hydrothermal in situ sulfuration–sputtering method. Compared with Cu2O/ZnO, Cu2O/ZnS/ZnO exhibited a higher transmittance of ∼85%, photovoltaic enhancement by ∼1.2 × 103-fold (a photovoltaic conversion efficiency of ∼1.28%), and stable output during a 6 month cycle. This can be primarily attributed to the in situ dual functional ZnS transition layer, which exhibits an appropriate Fermi level and high quantum yield, thereby efficiently optimizing the carrier equilibrium while sustaining higher transparency. Furthermore, the ZnS/ZnO core–shell nanoarrays with a better carrier transport pathway and increased solar efficiency can optimize the carrier kinetic equilibrium. In addition, the ZnS/ZnO nanoarrays with higher physical stability and in situ ZnS shell with higher chemical stability can efficiently increase the photovoltaic stability.

Compound SnS2 sensitizer in the S-scheme of Ag2Mo2O7/CoMoO4 heterojunction to improve the hydrogen evolution of semiconductor powder

The heterojunction construction can effectively regulate the carrier transport pathway. Ag2Mo2O7/CoMoO4 composite molybdate material was successfully synthesized by one step hydrothermal calcination method. The preparation method makes the contact of the two molybdate salts closer, forming a stable S-scheme heterojunction. Then SnS2 was added under physical agitation to improve the mobility of photogenerated carriers. The excellent structure of the ternary composite catalyst was proved by morphology and element analysis. The electron transfer mechanism of the S-scheme heterojunction was studied by photoelectric chemical test and spectral analysis. Because of the successful construction of S-scheme heterojunction and the introduction of sensitizer SnS2, the composite catalyst showed excellent hydrogen evolution performance (1599 μmol·g−1·h−1). This is because the S-scheme heterojunction and the sensitizer cooperatively promote the electron accumulation at the conduction band of CoMoO4. This work will provide a new strategy for molybdate in a heterojunction construction scheme.

Hole scavenger-free nitrogen photofixation in pure water with non-metal B-doped carbon nitride: Implicative importance of B species for N2 activation

Being the energy glutton and top ranker of greenhouse gas emission, Haber-Bosch is undoubtedly a grand challenge to reaching sustainability and carbon neutrality. Solar-driven nitrogen (N2) fixation under mild conditions is highly attractive and promising for sustainable ammonia (NH3) production. However, low conversion efficiency remains as a serious problem yet to be solved due to the difficult activation of strongly non-polar NN bond. In this study, defective and atomically thin g-C3N4 with boron sites was synthesized via a facile decomposition-thermal polymerization technique. The optimum photocatalyst displayed an NH3 yield of 213.59 μmol gcat−1 h−1 under visible light irradiation (λ > 400 nm) without any hole scavenger, bestowing high suitability for N2 fixation in pure water. The impressive performance is largely ascribed to the introduction of B species, which could act as the active sites for N2 adsorption, activation and reduction. Additionally, the atomically thin layer (∼3.25 nm) shortens charge carrier transport pathway while the B atoms and defects suppress quantum size effect as well as extends photo-response through bandgap reduction. These attributes synergistically lead to suppressed electron-hole recombination, efficacious charge transport, enhanced light utilization and enriched catalytic sites for N2 fixation. As a whole, this work presents an easy strategy to realize efficient N2 photofixation over a metal-free, low-cost and non-toxic photocatalyst in pure water as a continuous effort in advancing the burgeoning field of photocatalytic N2 fixation.

Covalent Organic Frameworks as Emerging Battery Materials

AbstractCovalent organic frameworks (COFs) are emerging as promising energy storage materials due to their unique characteristics, such as adjustable thickness, designable topology, superior stability and controllable pore size distribution. Consequently, COFs can provide diversified high‐rate carrier transport pathways, and the performance of COFs can be easily improved by adjusting conjugated skeleton types, overlapping p‐electron clouds between stacks, and modifying open channels with functional groups. The state‐of‐the‐art COFs electrode materials based on synthetic method and electrochemical performance in recent years are summarized and discussed in this review. The synthesis method, topological structure and application in metal ion (such as Li+, Na+, K+, Zn2+, Mg2+, Al3+, et. al) batteries of COFs electrodes are critically accounted. Finally, we briefly discuss the major challenges in the field that needs to be addressed to pave the way for industrial applications. Although there are still many arduous tasks to be tackled, the burgeoning of COFs‐related technologies and applications in batteries provide a ponderable field for commercial process in the short run.

Tuning the Carrier Transfer Behavior of Coaxial ZnO/ZnS/ZnIn2 S4 Nanorods with a Coherent Lattice Heterojunction Structure for Photoelectrochemical Water Oxidation.

Serious degradation and the short photogenerated carrier lifetime for the wide-bandgap semiconductor ZnO have become prominent issues that negatively affect photoelectrochemical (PEC) water splitting. Herein, a novel electron transport pathway was constructed by simple but effective coaxial growth of ZnO/ZnS/ZnIn2 S4 heterostructure nanoarrays to increase the carrier separation efficiency. This new photoanode fulfilled the requirements of both favorable band alignment and stability, achieving a stable photocurrent density of 1.146 mA cm-2 at 1.2 VRHE , which was approximately twice that of pristine ZnO. Detailed experimental studies revealed that the improved PEC activity was due to the lattice-matching interface coherency that activated the carrier transport pathway, giving rise to an optimized interfacial electronic structure for promoted charge separation by the built-in electric field and strengthened water oxidation activity. This design may provide a new approach to fabricating various efficient lattice-matching coherent interface photoanodes for PEC water splitting.

Understanding and Controlling the Evolution of Nanomorphology and Crystallinity of Organic Bulk‐Heterojunction Blends with Solvent Vapor Annealing

Solvent vapor annealing (SVA) has been shown to significantly improve the device performance of organic bulk‐heterojunction solar cells, yet the mechanisms linking nanomorphology, crystallinity of the active layer, and performance are still largely missing. Here, the mechanisms are tackled by correlating the evolution of nanomorphology, crystallinity, and performance with advanced transmission electron microscopy methods systematically. Model system of DRCN5T:PC71BM blends are SVA treated with four solvents differing in their donor and acceptor solubilities. The choice of solvent drastically influences the rate at which the maximum device efficiency establishes, though similar values can be achieved for all solvents. The donor solubility is identified as a key parameter that controls the kinetics of diffusion and crystallization of the blend molecules, resulting in an inverse relationship between optimal annealing time and donor solubility. For the highest efficiency, optimum domain size and single‐crystalline nature of DRCN5T fibers are found to be crucial. Moreover, the π–π stacking orientation of the crystallites is directly revealed and related to the nanomorphology, providing insight into the charge carrier transport pathways. Finally, a qualitative model relating morphology, crystallinity, and device efficiency evolution during SVA is presented, which may be transferred to other light‐harvesting blends.

Inexpensive and highly controlled growth of zinc oxide nanowire: Impacts of substrate temperature and growth time on synthesis and physical properties

Zinc oxide nanowires (ZnO NWs) were synthesized using a simple reactive-evaporation method without the use of catalysts. The NWs growth was precisely controlled by adjusting the experimental conditions mainly growth times and substrate temperatures. These experimental parameters are crucial for the growth of NWs. The typical diameter and length of the highly crystalline NWs obtained are several tens and several hundred nanometers, respectively. The nature of early-stages growth, morphology, structure and photoluminescent properties of the NWs grown at low temperatures have been explained and give the basic reasons behind these growth mechanisms. Self-organized ZnO nuclei are primarily formed on FTO pits due to high density of Zn atoms. It can be ascribed to vapour-solid with an area selected growth of NWs which provide a continuous pathway for carrier transport due to direct contact with the substrate. These features are crucial for the application of electronic devices, solar cells, etc.

Hydrogen-bonded dimers of mono-alkylated diketopyrrolopyrroles and their physical properties

Judicious utilization of hydrogen bonding in diketopyrrolopyrroles (DPPs) could allow smooth carrier transfer when applied to organic semiconducting materials. In this study, we determined the association constants of dimerization by hydrogen bonding for a mono-alkylated DPP in the solution state to obtain basic insights that could aid in the utilization of hydrogen bonding. The IR spectroscopy, thermal analysis, and X-ray diffractometry results demonstrate that the hydrogen-bonded dimer structure was preferentially formed in the solid state. Electron transporting properties was only observed in the DPP derivatives, forming the hydrogen-bonded dimer structure, indicating the formation of a film morphology suitable for carrier-transport pathway.

Self-assembled multifunctional nanostructures for surface passivation and photon management in silicon photovoltaics

Abstract This work reports the fabrication and characterization of multifunctional, nanostructured passivation layers formed using a self-assembly process that provide both surface passivation and improved light trapping in crystalline silicon photovoltaic (PV) cells. Scalable block copolymer self-assembly and vapor phase infiltration processes are used to form arrays of aluminum oxide nanostructures (Al2O3) on crystalline silicon without substrate etching. The Al2O3 nanostructures are characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and spectroscopic ellipsometry. Injection-level dependent photoconductance measurements are used to determine the effective carrier lifetime of the samples to confirm the nanostructures successfully passivate the Si surface. Finite element method simulations and reflectance measurement show that the nanostructures increase the internal rear reflectance of the PV cell by suppressing the parasitic optical losses in the metal contact. An optimized morphology of the structures is identified for their potential use in PV cells as multifunctional materials providing surface passivation, photon management, and carrier transport pathways.