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Enhanced photovoltaic performance of quinoxaline-based small molecules through incorporating trifluoromethyl substituents
摘要： Two D-A-D type quinoxaline-based small molecules have been synthesized by Suzuki coupling reaction for solution-processable organic photovoltaic cells (OPVs). The electron-donating triphenyl-amine was connected to both ends of an electron-withdrawing 2,3-diphenylquinoxaline core through thiophene bridge to produce QxTPA. In addition, QxCF3TPA was formed by introducing strong electron-withdrawing trifluoromethyl (CF3) groups into the para-position of the phenyl ring at the 2,3-position of quinoxaline core in QxTPA to explore their effect on the various properties of small molecules. The finding revealed the significant contributions of CF3 substituents in enhancing the photovoltaic performances of OPVs with QxCF3TPA compared to the reference case with QxTPA.
关键词： Small molecules,triphenylamine,trifluoromethyl,organic photovoltaic cell,2,3-diphenylquinoxaline
更新于2025-09-19 17:13:59
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Asymmetric 9,9a?2-bifluorenylidene-based small molecules as the non-fullerene acceptors for organic photovoltaic cells
摘要： Three new asymmetric 9,9'-bifluorenylidene-based derivatives, 2,7-dibutoxyl-3',6'-bis(5-methylenemalononitrile-3-octylthiophen-2-yl)-9,9'-bifluorenylidene (BF-TDCN2), 2,7-dibutoxyl-3',6'-bis(5-(methylene-indene-1,3-dione)-3-octylthiophen-2-yl)-9,9'-bifluorenylidene (BF-TID2) and 2,7-dibutoxyl-3',6'-bis(5-(2-methylene-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile)-3-octylthiophen-2-yl)-9,9'-bifluorenylidene (BF-TDCI2), were successfully synthesized by grafting different electron-withdrawing groups (malononitrile (DCN), 1H-indene-1,3(2H)-dione (ID) and 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (DCI)), which were used as the electron acceptors for organic photovoltaic cells. By changing the electron-withdrawing ability of the terminal group, the molecular energy level and band gap can be easily adjusted. The optical bandgaps of the three compounds in the thin films decreased with increasing the electron-withdrawing ability of the terminal group. Besides, the lateral chains of alkoxy groups located at the asymmetric end also play a certain influence on the solubility, molecular aggregation and the miscibility with polymer donor. Among these electron acceptors, the photovoltaic cell fabricated PBDB-T:BF-TDCI2 exhibited a maximum power conversion efficiency of 4.85% with an open-circuit voltage of 0.88 V and a low energy loss of 0.62 eV. By investigating different processing processes, the results showed that the power conversion efficiency can be improved by 20% with simple solvent annealing treatment. Through further study on the morphology and photophysical properties of the active layers, it was found that the processed device had better phase separation size and morphology, which was favorable to enhancing the intermolecular interaction, thus improving exciton separation and charge transfer in the active layer.
关键词： Non-fullerene acceptor,Organic photovoltaic cell,9,9'-bifluorenylidene derivative,Asymmetric molecule
更新于2025-09-19 17:13:59
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Tailoring morphology compatibility and device stability by adding PBDTTPD-COOH as third component to fullerene-based polymer solar cells
摘要： The crystallinity and morphology of polymer and fullerene have a profound influence on the performance of bulk heterojunction (BHJ) organic photovoltaic devices. The poor compatibility of donor and acceptor molecules in the BHJs hinders the further improvement of the device performance and stability in organic solar cells. In this work, the conjugated polymer PBDTTPD-COOH is introduced as a third component into BHJ films of PTB7-Th:PC71BM and PffBT4T-2OD:PC71BM to improve the crystallinity and morphology. The crystallinity of both donor polymers is enhanced and more face-on orientated crystals are observed in the corresponding films, which is correlated with the improvement of the current density of the related solar cells. Also, the improved BHJ morphology leads to an increased fill factor. Furthermore, the device stability significantly increases by the addition of the third component PBDTTPD-COOH. The T80 lifetime value is enhanced 10 times in the doped devices as compared with the binary solar cells in the case of the PTB7-Th:PC71BM series.
关键词： stability,crystallinity,organic photovoltaic,additive,face-on orientation
更新于2025-09-19 17:13:59
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Nonfullerene organic photovoltaic cells exhibiting 13.76% efficiency by employing upside‐down solvent vapor annealing
摘要： Organic photovoltaic cells (OPVs) are fabricated with a polymer donor PM7 and a nonfullerene acceptor IT‐4Cl; the morphology of active layers is optimized by employing upside‐down solvent vapor annealing (UD‐SVA) method with different annealing solvents. The OPVs with CS2 as annealing solvent exhibit optimized power conversion efficiency (PCE) of 13.76%, with simultaneously increased short‐circuit current density (JSC) of 20.53 mA cm?2 and fill factor (FF) of 77.05%. More than 15% PCE improvement can be achieved by employing CS2 UD‐SVA treatment, which should be attributed to slightly enhanced photon harvesting, efficient exciton separation, charge transport, and collection, resulting from the well‐developed morphology of active layer. Moreover, the PM7:IT‐4Cl–based OPVs with CS2 as annealing solvent still can maintain PCE more than 13% in a wide treatment time range from 20 to 90 seconds. This work demonstrated that UD‐SVA has great potential in improving the performance of nonfullerene OPVs.
关键词： phase separation,organic photovoltaic cells,solvent vapor annealing,nonfullerene
更新于2025-09-19 17:13:59
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Tuning the hybridization of local exciton and chargea??transfer states in highly efficient organic photovoltaic cells
摘要： Decreasing the energy loss is one of the most feasible ways to improve the efficiencies of organic photovoltaic (OPV) cells. Recent studies have suggested that non-radiative energy loss ( ) is the dominant factor that hinders further improvements in state-of-the-art OPV cells. However, there is no rational molecular design strategy for OPV materials with suppressed . In this work, taking molecular surface electrostatic potential (ESP) as a quantitative parameter, we establish a general relationship between chemical structure and intermolecular interactions. The results reveal that increasing the ESP difference between donor and acceptor will enhance the intermolecular interaction. In the OPV cells, the enhanced intermolecular interaction will increase the charge transfer (CT) state ratio in its hybridization with local exciton to facilitate the charge generation but simultaneously result in a larger . These results suggest that finely tuning the ESP of OPV materials is a feasible method to further improve the efficiencies of OPV cells.
关键词： hybridization,charge transfer state,intermolecular interaction,organic photovoltaic cells,non-radiative energy loss
更新于2025-09-19 17:13:59
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COMPARISON OF PERFORMANCES OF ORGANIC PHOTOVOLTAIC CELLS USING SubPc AS CENTRAL AMBIPOLAR LAYER IN TERNARY STRUCTURES AND AS ELECTRON ACCEPTOR IN BINARY STRUCTURES
摘要： We compare the performances of organic photovoltaic cells (OPVCs) based on binary and ternary planar heterojunctions. The organic active layers are pentathiophene (5T), subphthalocyanine (SubPc) and fullerene (C60). SubPc being an ambipolar material we used it either as electron acceptor in binary OPVCs or as central layer in ternary cells in order to increase the efficiency of OPVCs using 5T as electron donor. So, the different OPVC configurations were 5T/C60, 5T/SubPc and 5T/SubPc/C60. The effect of the different organic layer thicknesses on the device performances was studied. In order to understand the behavior of the different OPVC configurations, we proceeded with a morphological study. The influence of the high roughness of the 5T layer on the OPVCs performances is discussed. The best OPVCs performances are obtained with the binary structure 5T/SubPc. Its maximum efficiency corresponds to an increase of 50% compared to the OPVC based on the couple 5T/C60. External Quantum Efficiency measurements show that both layers participate to the current generation. The efficiency increase is mainly due to the increase of the open circuit voltage (Voc). In the case of ternary OPVCs, Voc is limited by the band structure of 5T and C60, moreover, the efficiency is also limited by the poor charge collection efficiency of the ternary structure and the series resistance of the three stacked organic layers.
关键词： Organic photovoltaic cells,ternary structures,pentathiophene,subphthalocyanine,binary structures
更新于2025-09-19 17:13:59
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17.1%-Efficiency organic photovoltaic cell enabled with two higher-LUMO-level acceptor guests as the quaternary strategy
摘要： Quaternary blended organic solar cells utilize four blended material components (one donor plus three acceptors, two donors and two acceptors, or three donors plus one acceptor) as the active layer materials. The use of four material components allows us to have more material selections and more mechanism choices to improve the photon-to-electron conversion efficiency. In this contribution, we present a new case of quaternary material system, that shows 17.1% efficiency obtained by adding IDIC and PC71BM as the guest acceptors of the host binary of PM6:Y6. The lowest unoccupied molecular orbital (LUMO) levels of IDIC and PC71BM are both higher than that of Y6, which is one reason to obtain increased open-circuit voltage (Voc) in the quaternary device. Upon introduction of IDIC and PC71BM as the acceptor guests, the hole and electron mobilities are both increased, which contributes to the increased short-circuit current-density (Jsc). Effects of the weight ratios of the three acceptor components are investigated, which demonstrates that the increased hole and electron mobilities, the accelerated hole-transfer, and the reduced monomolecular recombination are the factors contributing to the increased Jsc and fill-factor. This case of quaternary device demonstrates the applicability of the quaternary strategy in increasing the device functions and hence the efficiencies in the field of organic photovoltaic cells.
关键词： small-molecule acceptor,organic photovoltaic,quaternary solar cell,nonfullerene,fullerene
更新于2025-09-19 17:13:59
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[IEEE 2019 Global LIFI Congress (GLC) - Paris, France (2019.6.12-2019.6.13)] 2019 Global LIFI Congress (GLC) - LiFi Reception from Organic Photovoltaic Modules Subject to Additional DC Illuminations and Shading Effects
摘要： In this paper, we study the performance of organic photovoltaic (OPV) modules as LiFi receivers in two specific configurations. The PV-based LiFi receiver is first exposed to an additional homogeneous light source with different intensity levels and then the influence of partial lighting is studied (shading effect). In both cases, we compare the sensibility and the cutoff frequency of LiFi transmission when the solar cell is operated either in short-circuit mode (i.e. when it is loaded with an active transimpedance amplifier) or in open circuit mode (i.e. when it is terminated with an high impedance passive load). While the OPV module performance decreases in open-circuit mode as a function of the DC illumination level, we observe an improvement of the cutoff frequency in short circuit mode. This result seems very promising for outdoor LiFi transmissions but also for indoor conditions where natural light can disturb LiFi communications. Theoretical explanations involving physical parameters for energy harvesting (carrier mobility, lumped series resistance) are proposed to justify the observed behaviors. Finally, experimental results of shaded solar cells are provided in the two operating modes (open-circuit and short-circuit). We show that sensibility and bandwidth of OPV modules strongly depend on both the shading configuration and the operating mode.
关键词： OPV,shading effects,LiFi,open-circuit mode,organic photovoltaic,short-circuit mode
更新于2025-09-16 10:30:52
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The Role of Mineral Acid Doping of PEDOT:PSS and Its Application in Organic Photovoltaics
摘要： Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is one of the most successful conducting polymers in terms of commercialization. A method to readily obtain highly conductive and transparent PEDOT:PSS films is urgently needed. A simple method is introduced to enhance the conductivity of such films dramatically. By adding a series of mineral acids into the PEDOT:PSS aqueous solution directly, the conductivity is enhanced by 3–4 orders of magnitude. Mechanistic study reveals that the conductivity enhancement is dependent on boiling point, pKa value, softness parameter, and oxidability of the dopant acid. Specifically, acids with high boiling point, low pKa, and low softness parameter are able to induce phase separation between PEDOT and PSS, leading to secondary doping. If the dopant acid exhibits strong oxidability, the conductivity can also be enhanced via primary doping. H2SO4-doped PEDOT:PSS films exhibit the highest conductivity of 2244 S cm?1. These films are employed as the transparent electrodes of poly(3-hexylthiophene-2,5-diyl) (P3HT)-based organic photovoltaic cells, and the power conversation efficiency reaches 3.13%. These results suggest direct acid doping of PEDOT:PSS solution is a facile approach to obtain highly flexible transparent electrodes.
关键词： transparent flexible electrodes,PEDOT:PSS doping,organic photovoltaic cells
更新于2025-09-16 10:30:52
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Morphological Study of Blend Thin Films of Poly(3-hexylthiophene)-<i>block</i>-polyisobutylene-<i>block</i>-poly(3-hexylthiophene):Poly(3-hexylthiophene) and Their Application to Photovoltaics
摘要： The detailed morphological studies of poly(3-hexylthiophene)(P3HT)-b-polyisobutylene(PIB)-b-P3HT:P3HT blend thin films by grazing incidence X-ray scattering (GIXS) were reported. The results of GIXS experiments indicated the formation of phase separation between P3HT and PIB domains even after blending the P3HT homopolymer below 30 wt%. The change in d-spacing values of the phase-separated under strains was suppressed by increasing the weight ratio of the P3HT homopolymer, probably due to the disruption of the microphase separation. The blending the P3HT homopolymer induced the edge-on orientation during the strain process below 75%, probably by improving the interaction between P3HT domains in the blend thin films. The OPV characteristics were obtained with the device structure of ITO/PEDOT:PSS/P3HT-b-PIB-b-P3HT:P3HT:PC61BM/Ca/Al, significantly improving the JSC and FF values by increasing the P3HT homopolymer weight ratio. The excellent elongation behavior of P3HT-b-PIB-b-P3HT:P3HT blend bulk films (P3HT < 30 wt%) could be achieved, probably due to the formation of microphase separation between semi-crystalline P3HT and rubbery PIB domains.
关键词： Organic photovoltaic,Morphology,Block copolymer,π-Conjugated polymer,Elastomer,Synchrotron X-ray scattering
更新于2025-09-16 10:30:52