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Two-Dimensional Bi <sub/>2</sub> O <sub/>2</sub> Se with High Mobility for High-Performance Polymer Solar Cells
摘要： Carrier mobility is a critical factor for power conversion efficiency (PCE) of polymer solar cells (PSCs), and the low charge carrier mobility still limits performance improvement of PSCs. Adding high mobility material into the active layer is one of the better ways to enhance the PCE of PSCs. Two-dimensional (2D) Bi2O2Se can be an ideal additive material for improving the carrier mobility of PSCs because its ultrahigh mobility and high thermal stability. In this work, the Bi2O2Se few-layer 2D nanoflakes are fabricated by combining lithium intercalation with shear force-assisted liquid phase exfoliation and applied as an additive to promote charge transport in PSCs for the first time. The 2D Bi2O2Se nanoflakes, when introduced into the active layer, not only provide new interface between donor and acceptor and efficient charge transfer pathways but also induce crystallization of photosensitive layer and form the continuous interpenetrating networks, which promotes the exciton separation and charge transfer in photosensitive layer. As a result, the PCE of device based on PBDB-T:ITIC is increased from 10.09% (0 wt%) to 12.22% (2 wt%). Meanwhile, the PCE of device based on PM6:Y6 is also increased from 14.59% for binary device to 16.28% for optimized ternary device (2 wt%). Moreover, the optimized ternary device shows excellent air stability by suppressing the mixing of the two phases. This work supplies a good method to enhance the PCE of PSCs, also shows the Bi2O2Se material has a good prospect in photovoltaic devices.
关键词： crystallinity,charge recombination,Polymer solar cells,stability,carrier mobility,2D Bi2O2Se flakes
更新于2025-09-19 17:13:59
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Built-in voltage enhanced by in-situ electrochemical polymerized undoped conjugated hole-transporting modifier in organic solar cells
摘要： Herein, a new electropolymerized (EP) film named poly-triphenylcarbazole fluoranthene (p-TPCF) has been in-situ synthesized by electrochemical cyclic voltammetry method, and applied to tune the work-function (WF) of the PEDOT:PSS hole-transporting layer (HTL) in organic solar cells (OSCs). Multi techniques, including Kelvin probe force microscopy (KPFM), light intensity dependent solar cell characterization, Mott-Schottky analysis, transient photovoltage (TPV) and transient photocurrent (TPC) measurements, have been explored to provide insights into the mechanism. Benefiting from deeper work-function (WF), larger built-in voltage (Vbi), decreased recombination, longer carrier lifetime, the devices with EP film exhibited superior device performance with simultaneously enhanced Voc, Jsc and FF.
关键词： PEDOT:PSS,built-in voltage,work-function tuning,organic solar cells,carrier lifetime,electropolymerized film,charge recombination
更新于2025-09-19 17:13:59
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Highly Stabilized Quantum Dot Ink for Efficient Infrared Light Absorbing Solar Cells
摘要： Liquid-state ligand exchange provides an efficient approach to passivate a quantum dot (QD) surface with small binding species and achieve a QD ink toward scalable QD solar cell (QDSC) production. Herein, experimental studies and theoretical simulations are combined to establish the physical principles of QD surface properties induced charge carrier recombination and collection in QDSCs. Ammonium iodide (AI) is used to thoroughly replace the native oleic acid ligand on the PbS QD surface forming a concentrated QD ink, which has high stability of more than 30 d. The ink can be directly applied for the preparation of a thick QD solid film using a single deposition step method and the QD solid film shows better characteristics compared with that of the film prepared with the traditional PbX2 (X = I or Br) post-treated QD ink. Infrared light-absorbing QDSC devices are fabricated using the PbS-AI QD ink and the devices give a higher photovoltaic performance compared with the devices fabricated with the traditional PbS-PbX2 QD ink. The improved photovoltaic performance in PbS-AI-based QDSC is attributed to diminished charge carrier recombination induced by the sub-bandgap traps in QDs. A theoretical simulation is carried out to atomically link the relationship of QDSC device function with the QD surface properties.
关键词： quantum dots,charge recombination,solar cells,theoretical simulations,ligand exchange
更新于2025-09-19 17:13:59
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Phenanthrenea??Fuseda??Quinoxaline as Key Building Block for Highly Efficient and Stable Sensitizers in Copper Electrolyte Based Dyea??Sensitized Solar Cells
摘要： Dye-sensitized solar cells (DSSCs) based on Cu(II/I) bipyridyl or phenanthroline complexes as redox shuttles have achieved very high open-circuit voltages (VOC, > 1 V). However, their short-circuit photocurrent density (JSC) has remained modest. The challenge for increasing the JSC is expected to extend the spectral response of sensitizers to the red or NIR region while maintaining efficient electron injection in the mesoscopic TiO2 film and fast regeneration by the Cu(I) complex. Here, we report two new D-A-π-A featured sensitizers coded HY63 and HY64, which employ either benzothiadiazole (BT) or phenanthrene-fused-quinoxaline (PFQ) as the auxiliary electron-withdrawing acceptor moiety. In spite of very similar energy levels and absorption onsets, HY64-based DSSCs outperform largely their HY63 counterpart, achieving an outstanding power conversion efficiency (PCE) of 12.5% with superior stability. In depth studies of interfacial charge carrier dynamics show that PFQ is superior to BT in retarding charge recombination resulting in near quantitative collection of photogenerated charge carriers.
关键词： sensitizers,light-harvesting,dye-sensitized solar cells,copper redox shuttle,charge recombination
更新于2025-09-19 17:13:59
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Tri-functionalized TiO Cl4-2 accessory layer to boost efficiency of hole-free, all-inorganic perovskite solar cells
摘要： Tin dioxide (SnO2) is generally regarded as a promising electron-transporting layer (ETL) for state-of-the-art perovskite solar cells (PSCs), however, the ubiquitous oxygen-vacancy-related defects at SnO2 surface and the large energy difference between conduction band of SnO2 and perovskite layer undoubtedly cause severe charge carrier recombination, resulting in sluggish charge extraction efficiency and non-negligible open-circuit voltage (Voc) loss. Herein, a chlorine-containing TiOxCl4-2x accessory layer is fabricated by immersing SnO2 layer into the TiCl4 aqueous solution to passivate the surface oxygen-vacancy-related defects of SnO2 layer and to set an intermediate energy level at ETL/perovskite interface in all-inorganic cesium lead tri-bromine (CsPbBr3) PSCs. Furthermore, the TiOxCl4-2x layer also improves the infiltration of SnO2 layer surface toward perovskite precursor for high-quality perovskite film. Finally, the hole-free, all-inorganic CsPbBr3 PSC with a structure of FTO/SnO2/TiOxCl4-2x/Cs0.91Rb0.09PbBr3/carbon achieves a champion efficiency of 10.44% with a Voc as high as 1.629 V in comparison to 8.31% for control device. Moreover, the optimized solar cell presents good stability in 80% humidity in air.
关键词： Electron-transporting layer,Stability,All-inorganic perovskite solar cells,Charge recombination,Cesium lead bromine
更新于2025-09-19 17:13:59
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Interface configuration effects on excitation, exciton dissociation, and charge recombination in organic photovoltaic heterojunction
摘要： The morphology of donor-acceptor heterojunction interface significantly affects the electron/hole processes in organic solar cells, including charge transfer (CT), exciton dissociation (ED), and charge recombination (CR). Here, to investigate interface molecular configuration effects, the donor-acceptor complexes with face-on, edge-on, and end-on configurations were constructed as model systems for the p-SIDT(FBTTh2)2/C60 heterojunction. The geometries, electronic structures, and excitation properties of monomers and the complexes with three configurations were studied based on density functional theory (DFT) and time-dependent DFT calculations with optimally tuned range separation parameters and solid polarization effects. In terms of Marcus theory, the rate constants of ED and CR processes were analyzed. The results show that most of the excited states for p-SIDT(FBTTh2)2 exhibit an intramolecular CT character, and the similarity of the excitation characters (CT and local excitation) and energies among three complexes with different configurations indicate that the electronic structure and excitation properties are insensitive to the interfacial molecular configurations. However, the rates of ED and CR processes heavily depend on it. These results underline the importance of controlling molecular configuration and then the morphology at the heterojunction interface in organic solar cells.
关键词： organic heterojunction interface,charge transfer,electronic structure,charge recombination
更新于2025-09-16 10:30:52
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Unraveling the Structure-Property Relationship of Molecular Hole Transporting Materials for Perovskite Solar Cells
摘要： Clarifying the structural basis and microscopic mechanism lying behind electronic properties of molecular semiconductors is of paramount importance in further materials design to enhance the performance of perovskite solar cells. In this paper, three conjugated quasi-linear segments of 9,9-dimethyl-9H-fluorene, 9,9-dimethyl-2,7-diphenyl-9H-fluorene, and 2,6-diphenyldithieno[3,2-b:2',3'-d]thiophene are end-capped with two bis(4-methoxyphenyl)amino groups for structurally simple molecular semiconductors Z1, Z2, and Z3, which crystalline in the monoclinic, triclinic, and monoclinic space groups, respectively. The modes and energies of intermolecular noncovalent interactions in various closely packed dimers extracted from single crystals are computed based on the quantum theory of atoms in molecules and energy decomposition analysis. Transfer integrals, reorganization energies, and center-of-mass distances in these dimers as well as band structures of single crystals are also calculated to define the theoretical limit of hole transport and microscopic transport pictures. Joint X-ray diffraction and space-charge limiting current measurements on solution-deposited films suggest the dominant role of crystallinity in thin film hole mobility. Photoelectron spectroscopy and photoluminescence measurements show that an enhanced interfacial interaction between perovskite and Z3 could attenuate the adverse impact of reducing the energetic driving force of hole extraction. Our comparative studies show that molecular semiconductor Z3 with a properly aligned HOMO energy level and a high thin film mobility can be employed for efficient perovskite solar cells, achieving a good power conversion efficiency of 20.84%, which is even higher than that of 20.42% for spiro-OMeTAD control.
关键词： charge recombination,perovskite solar cell,molecular crystal,noncovalent interaction,crystallinity,charge transport,organic semiconductor
更新于2025-09-16 10:30:52
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Mechanistic Insights into Solid-State p-Type Dye-Sensitized Solar Cells
摘要： The study of p-type dye sensitized solar cells (p-DSCs) is appealing but challenging. Although the devices have been studied for 20 years, light conversion efficiency is lag far behind those of n-DSCs. Very recently, on the basis of a core-shell structure, a novel solid-state p-DSC (p-ssDSCs) has been fabricated, which showed great enhancement in open-circuit voltage and dye regeneration rate. To further improve the performance of such devices, charge diffusion, recombination process and the main limiting factors have to be understood. In the present paper, core-shell p-ssDSCs with ZnO as an electron conductor were fabricated by atomic layer deposition. The charge transport time was determined to be ca. 0.1 ms, which is about 2 orders of magnitude faster than those of typical liquid devices with I-/I3- as a redox mediator. As a consequence, the devices exhibit the highest reported apparent charge diffusion coefficient (Dapp) among p-DSCs. It is ascribed to an electron limiting diffusion process by the ambipolar diffusion model, suggesting a different charge transport determining mechanism in contrast to liquid p-DSCs. The charge recombination rate is 1-2 orders of magnitude slower than its charge transport time, resulting in that the estimated charge collection efficiency is near unity. Detailed analysis of the incident photon-to-electron conversion efficiency suggests, that the energy conversion efficiency in these p-ssDSCs is currently limited by a large fraction of dyes that is not fully electrically connected in the device.
关键词： solid-state,charge recombination,p-type dye sensitized solar cells,dye utilization fraction,charge transport
更新于2025-09-16 10:30:52
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Mediated Non-geminate Recombination in Ternary Organic Solar Cells Through a Liquid Crystal Guest Donor
摘要： The approach via ternary blends prompts the increase of absorbed photon density and resultant photocurrent enhancement in organic solar cells (OSCs). In contrast to actively reported high efficiency ternary OSCs, little is known about charge recombination properties and carrier loss mechanisms in these emerging devices. Here, through introducing a small molecule donor BTR as a guest component to the PCE-10:PC71BM binary system, we show that photocarrier losses via recombination are mitigated with respect the binary OSCs, owing to a reduced bimolecular recombination. The gain of the fill factor in ternary devices are reconciled by the change in equilibrium between charge exaction and recombination in the presence of BTR toward the former process. With these modifications, the power conversion efficiency in ternary solar cells receives a boost from 8.8 (PCE-10:PC71BM) to 10.88%. We further found that the voltage losses in the ternary cell are slightly suppressed, related to the rising charge transfer-state energy. These benefits brought by the third guest donor are important for attaining improvements on key photophysical processes governing the photovoltaic efficiencies in organic ternary solar cells.
关键词： charge transfer states,small molecule donor,voltage loss,ternary solar cells,charge recombination
更新于2025-09-16 10:30:52
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Influence of active layer thickness on photovoltaic performance of PTB7:PC70BM bulk heterojunction solar cell
摘要： In this paper, we studied the effect of active layer thickness on the photovoltaic performance of inverted bulk heterojunction (BHJ) organic solar cell (OSC). The capacitance-voltage (C–V), dark current-voltage (I–V) and impedance spectroscopy (IS) analysis were carried out to explain the active layer thickness dependence on the photovoltaic performance. The OSC with an active layer thickness of 150 nm achieved the best power conversion efficiency (PCE) of 5.87%, while the OSC of 200 nm active layer thickness yielded the worst PCE. Reduction in the fill factor (FF) was the main reason for the reduction in the PCE at large active layer thickness. The dark I–V analysis revealed large defect density for the OSC with active layer thickness of 200 nm, which raised the charge recombination and leakage current and consequently reduced the FF. IS analysis predicted that the charge transport became the serious limitations for the OSC with 200 nm thick active layer, which can be attributed to the weakening of electric field as well as creation of field-free regions. It mainly caused a drastic drop in the fill factor by reducing the charge collection efficiency, consequently deteriorated the photovoltaic performance.
关键词： Charge recombination,Bulk heterojunction solar cell,Ideality factor,Photovoltaic performance,Charge transport resistance,Leakage current
更新于2025-09-16 10:30:52