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Implementation of data-cube pumpa??probe KPFM on organic solar cells
摘要： An implementation of pump–probe Kelvin probe force microscopy (pp-KPFM) is reported that enables recording the time-resolved surface potential in single-point mode or over a 2D grid. The spectroscopic data are acquired in open z-loop configuration, which simplifies the pp-KPFM operation. The validity of the implementation is probed by measurements using electrical pumping. The dynamical photoresponse of a bulk heterojunction solar cell based on PTB7 and PC71BM is subsequently investigated by recording point-spectroscopy curves as a function of the optical power at the cathode and by mapping 2D time-resolved images of the surface photovoltage of the bare organic active layer.
关键词： Kelvin probe force microscopy (KPFM),time-resolved measurements,bulk heterojunctions,organic photovoltaics,pump–probe configuration,photocarrier dynamics
更新于2025-09-16 10:30:52
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Benzodithiophenedione-based polymers: recent advances in organic photovoltaics
摘要： Over the past 20 years, significant progress has been made in organic photovoltaics (OPVs) due to its advantages of being cost-effective, being lightweight, and having flexible manufacturability. The optical-active layer of OPVs consists of a p-type polymer as the donor and an n-type small molecule as the acceptor. An efficient design strategy of a polymer donor is based on an alternating electron-donating unit (D) and an electron-accepting unit (A). Among numerous electron-accepting units, an emerging annelated thiophene of benzodithiophenedione (BDD) has exhibited a distinguished photovoltaic performance because of its planar molecular structure, low-lying highest occupied molecular orbit (HOMO) level and good self-assembly property. In this review article, we summarize the most recent developments in BDD-based photovoltaic materials. Special attention is paid to the chemical structure-property relationships, such as the absorption, bandgap, energy levels, mobilities, and photovoltaic performances. The empirical regularities and perspectives on the future development of BDD-based photovoltaic materials are included.
关键词： chemical structure-property relationships,benzodithiophenedione,photovoltaic performance,polymer donors,organic photovoltaics
更新于2025-09-16 10:30:52
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Star-shaped A-D-A compounds synthesized by different methods and used as donor or acceptor materials in organic photovoltaics
摘要： Star-shaped small molecule has lots of fascinating advantages compare with the linear small molecule. In this paper, two star-shaped small-molecules (S-TT and S-TT-R) with vinyl trithiophene with or without alkyl substituents as core, N-ethyl- rhodanine as terminal and withdrawing groups, vinyl as bridge group were synthesized by different synthetic routes. Both of the two materials demonstrate high thermal stability and broad absorption. Both S-TT and S-TT-R exhibit narrow bandgap (1.72 and 1.82 eV), low LUMO energy levels (? 3.92 eV) for S-TT and high HOMO energy levels (? 5.37 eV) for S-TT-R which could be applied as acceptor or donor materials for photovoltaics, respectively. Both of the two compounds were used as donor materials with PC61BM acceptor and S-TT were used as acceptor material with P3HT donor.
关键词： Absorption,Star-shaped small molecule,Organic photovoltaics,Acceptor materials,Thermal stability,Donor materials
更新于2025-09-16 10:30:52
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Comparing C60 and C70 as acceptor in organic solar cells: influence of the electronic structure and aggregation size on the photovoltaic characteristics
摘要： The difference in aggregation size of the C60 and C70 fullerenes affect the photovoltaic performance of devices assembled in the so-called bilayer architecture with poly[2,7-(9,9- dioctyl- dibenzosilole)- alt-4,7- bis(thiophen-2-yl)benzo- 2,1,3- thiadiazole] (PSiF-DBT) as the electron donor material. Despite the better performance of the C70 devices, which is related to the high absorption coefficient in the visible range and the superior charge transport properties, the short-circuit current variation upon annealing treatment at 100oC is approximately twice bigger when the C60 is the acceptor. We attribute this effect to the tendency of C60 in form smaller aggregate domains relatively to the C70. The increased roughness on the polymeric surface after annealing results in an enhanced donor/acceptor contact area and assists the fullerene diffusion deeper inside the polymeric layer. This effect leads to a better mixing between donor and acceptor species and create a interpenetrating layer close to the so-called bulk heterojunction. Since C60 forms smaller aggregates, this mechanism is more pronounced for this molecule. Therefore, a significant variation in the performance of the C60 devices is observed after this kind of treatment. Density Functional Theory calculations of the potential energy of interaction between two fullerene molecules and X-Ray measurements gives evidences to support this idea. In addition, combining spectrally resolved external quantum efficiency measurements with optical modeling our results also indicate the occurrence of the bilayer interfacial mixing for PSiF-DBT/C60.
关键词： Transfer matrix method,Density functional theory,Aggregation size,Fullerenes,Organic photovoltaics
更新于2025-09-16 10:30:52
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Near‐infrared organic photoelectric materials for light‐harvesting systems: Organic photovoltaics and organic photodiodes
摘要： The inherent advantages of organic optoelectronic materials endow light-harvesting systems, including organic photovoltaics (OPVs) and organic photodiodes (OPDs), with multiple advantages, such as low-cost manufacturing, light weight, flexibility, and applicability to large-area fabrication, make them promising competitors with their inorganic counterparts. Among them, near-infrared (NIR) organic optoelectronic materials occupy a special position and have become the subject of extensive research in both academia and industry. The introduction of NIR materials into OPVs extends the absorption spectrum range, thereby enhancing the photon-harvesting ability of the devices, due to which they have been widely used for the construction of semitransparent solar cells with single-junction or tandem architectures. NIR photodiodes have tremendous potential in industrial, military, and scientific applications, such as remote control of smart electronic devices, chemical/biological sensing, environmental monitoring, optical communication, and so forth. These practical and potential applications have stimulated the development of NIR photoelectric materials, which in turn has given impetus to innovation in light-harvesting systems. In this review, we summarize the common molecular design strategies of NIR photoelectric materials and enumerate their applications in OPVs and OPDs.
关键词： organic photodiodes,near infrared,organic optoelectronic materials,organic photovoltaics
更新于2025-09-12 10:27:22
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Unraveling Correlations between Molecular Properties and Device Parameters of Organic Solar Cells Using Machine Learning
摘要： Understanding the relationships between molecular properties and device parameters is highly desired not only to improve the overall performance of an organic solar cell but also to fulfill the requirements of a device for a particular application such as solar to fuel energy conversion (high VOC) and solar-window applications (high JSC). In this work, a series of machine learning models are built for three important device characteristics (VOC, JSC, and FF) using 13 crucial molecular properties as descriptors, with an impressive predictive performance (r=0.7). These models may play a vital role in designing promising organic materials for a specific photovoltaic application with high VOC/JSC. The importance of descriptors for each device parameter is unraveled, which may assist in tuning them and improve understanding of the energy conversion process.
关键词： virtual screening,organic photovoltaics,machine learning,conjugated molecules,Organic solar cells
更新于2025-09-12 10:27:22
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Over 16.7% efficiency of ternary organic photovoltaics by employing extra PC71BM as morphology regulator
摘要： Ternary organic photovoltaics (OPVs) are fabricated with PBDB-T-2Cl:Y6 (1:1.2, wt/wt) as the host system and extra PC71BM as the third component. The PBDB-T-2Cl:Y6 based binary OPVs exhibit a power conversion efficiency (PCE) of 15.49% with a short circuit current (JSC) of 24.98 mA cm?2, an open circuit voltage (VOC) of 0.868 V and a fill factor (FF) of 71.42%. A 16.71% PCE is obtained in the optimized ternary OPVs with PBDB-T-2Cl:Y6:PC71BM (1:1.2:0.2, wt/wt) active layer, resulting from the synchronously improved JSC of 25.44 mA cm?2, FF of 75.66% and the constant VOC of 0.868 V. The incorporated PC71BM may prefer to mix with Y6 to finely adjust phase separation, domain size and molecular arrangement in ternary active layers, which can be confirmed from the characterization on morphology, 2D grazing incidence small and wide-angle X-ray scattering, as well as Raman mapping. In addition, PC71BM may prefer to mix with Y6 to form efficient electron transport channels, which should be conducive to charge transport and collection in the optimized ternary OPVs. This work provides more insight into the underlying reasons of the third component on performance improvement of ternary OPVs, indicating ternary strategy should be an efficient method to optimize active layers for synchronously improving photon harvesting, exciton dissociation and charge transport, while keeping the simple cell fabrication technology.
关键词： ternary strategy,organic photovoltaics,morphology regulator,organic solar cells,power conversion efficiency
更新于2025-09-12 10:27:22
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Slot-die processing and encapsulation of non-fullerene based ITO-free organic solar cells and modules
摘要： Organic photovoltaic (OPV) devices have shown remarkable performance progress in recent years, reaching current record power conversion efficiency (PCE) values of 16.4% for single junction and 17.3% for multi junction devices, owing mostly to the impressive developments made within synthesis of new non-fullerene acceptors. This progress places organic solar cells at the forefront of thin-film photovoltaic technology. However, in order to meet industrial demands and reach high performance values in industrial settings, further research and development efforts within Roll-to-Roll (R2R) and Sheet-to-Sheet (S2S) processing of OPV devices under ambient conditions are required. Furthermore, OPV modules being manufactured through such up-scaled processing techniques should ideally be developed from low cost materials, and show good stability towards various different operational stress conditions. In this work, we demonstrate combined R2R and S2S development of ITO-free OPV devices, which are based on the non-fullerene material system PBDB-T:ITIC. The devices are processed from R2R vacuum sputtering and S2S slot-die coating at ambient conditions, and reach cell PCE values of 5.5%. In addition, we introduce a correlation between different barrier films, both commercial and sputtered inorganic coatings on ultra-clean PET, and the lifetime of the developed devices. The results therefore demonstrate an important step in the development of OPV devices from R2R and S2S processes in industrial settings.
关键词： organic solar cells and modules,Roll-to-Roll (R2R),Sheet-to-Sheet (S2S),organic photovoltaics (OPV),slot-die coating,device encapsulation,non-fullerene acceptors
更新于2025-09-12 10:27:22
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Sputter deposited titanium oxide layers as efficient electron selective contacts in organic photovoltaic devices
摘要： Organic photovoltaics (OPV) has recently reached power conversion efficiencies of 17.3%, making it a green technology that not only offers short energy payback times and diverse photovoltaic integration schemes, but also can deliver competitive power outputs. OPV typically employs electron selective contact layers made from low work function n-type metal oxide semiconductors, such as titanium oxide (TiO2) or zinc oxide (ZnO), developed from a variety of deposition techniques. However, in the case of TiO2 interlayers, the appearance of unwanted s-shape characteristics has been reported extensively in the literature in the past, for a variety of different deposition method used. It has been shown that the s-shape arises from negatively charged chemisorbed oxygen, and that it can be deactivated by UV light illumination, which, however, is hardly compatible with real-life OPV application. In this work, we introduce sputtered crystalline titanium oxide layers as efficient s-shape-free electron selective extraction layers in organic solar-cell devices. We demonstrate that the onset of crystallization takes place at substrate growth temperatures of around 100°C for the TiOx thin films, and that the crystallization onset temperature correlates well with a strong increase in device performance, and the removal of any s-shape characteristics. Optical, structural, compositional and electronic energy-level characterizations of the TiOx layers are shown in the present work, and point to the formation of an oxide with a low surface-defect density, developed from the sputter-crystallization process. Importantly, well-functioning s-shape free PTB7:PC70BM devices are demonstrated for TiOx growth temperatures of 155°C.
关键词： Sputter Deposition,Metal Oxide Interlayers,S-Shape Free,Titanium Oxide,Organic photovoltaics
更新于2025-09-12 10:27:22
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Disorder vs Delocalization: Which Is More Advantageous for High-Efficiency Organic Solar Cells?
摘要： We investigate the combined influence of energetic disorder and delocalization on electron-hole charge-transfer state separation efficiency in donor-acceptor organic photovoltaic systems using an analytical hopping model and Monte Carlo calculations, coupled with an effective mass model. Whereas energetic disorder increases the separation yield at intermediate and low electric fields for low efficiency blends with strongly localized carriers, we find that it reduces dramatically the fill factors and power conversion efficiencies in high efficiency solar cells that require high carrier delocalization within the conjugated segment and high mobility-lifetime product. We further demonstrate that the initial electron-hole distance and thermalization processes play only a minor role in the separation dynamics.
关键词： Charge separation,delocalization,organic photovoltaics,disorder,Monte Carlo simulations
更新于2025-09-12 10:27:22