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A high-performance non-fullerene electron acceptor with bisalkylthiothiophene π-bridges for organic photovoltaics
摘要： A new non-fullerene small molecule acceptor IDT2ST-4F bearing a bisalkylthiothiophene unit as the p-bridge was designed and synthesized, which exhibited a low optical bandgap of 1.43 eV. The optimized organic solar cells based on PBDB-T:IDT2ST-4F gave a high power conversion efficiency (PCE) of 11.43% with a relatively low energy loss of 0.58 eV.
关键词： non-fullerene electron acceptor,power conversion efficiency,organic photovoltaics,bisalkylthiothiophene
更新于2025-09-12 10:27:22
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Machine learning–assisted molecular design and efficiency prediction for high-performance organic photovoltaic materials
摘要： In the process of finding high-performance materials for organic photovoltaics (OPVs), it is meaningful if one can establish the relationship between chemical structures and photovoltaic properties even before synthesizing them. Here, we first establish a database containing over 1700 donor materials reported in the literature. Through supervised learning, our machine learning (ML) models can build up the structure-property relationship and, thus, implement fast screening of OPV materials. We explore several expressions for molecule structures, i.e., images, ASCII strings, descriptors, and fingerprints, as inputs for various ML algorithms. It is found that fingerprints with length over 1000 bits can obtain high prediction accuracy. The reliability of our approach is further verified by screening 10 newly designed donor materials. Good consistency between model predictions and experimental outcomes is obtained. The result indicates that ML is a powerful tool to prescreen new OPV materials, thus accelerating the development of the OPV field.
关键词： organic photovoltaics,molecular design,machine learning,high-performance materials,efficiency prediction
更新于2025-09-12 10:27:22
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Organogels Based on PEDOT:PSS and Carbon‐dots for Efficient Hole Transport in Organic Photovoltaics
摘要： Organic photovoltaic devices (OPVs) have received great attention in the past decades for next-generation renewable energy sources due to the low production cost and ?exible structure. The structure of OPVs is commonly composed of anode, hole transport layer (HTL), photoactive layer, and cathode. In general, an electrically conducting polymer such as poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) is used as the HTL to improve interfacial properties between the anode and photoactive layer. The PEDOT:PSS consists of hydrophobic and conductive PEDOT-chains doped with hygroscopic insulator PSS, resulting in poor electrical properties. It has been known that treatment of PEDOT:PSS with polar organic solvent or acid and annealing caused the conformational change and thus improved the electrical conductivity. However, controlling the orientation and shape of the PEDOT in PEDOT:PSS is still a challenge for improving the electrical percolation pathway. Recently, the electrical conductivity of PEDOT:PSS has been enhanced by inducing the gelation of PEDOT through self-assembly with graphene oxide (GO) and/or graphene quantum dots (GQDs). Although the gelation of PEDOT:PSS improved its mechanical, thermal, and electrical properties, its morphological changes and gelation mechanism in thin ?lms have not been well understood. In this letter is described the development of reticulated charge–transporting networks with enhanced electrical properties of self-assembled PEDOT:PSS organogels containing carbon-dots. Carbon-dots acted as a physical linker with PEDOT-chains in PEDOT:PSS through electrostatic interactions, resulting in the formation of a core–shell (carbon-dot@PEDOT) nanostructure. Furthermore, the blending ratio of carbon-dots and PEDOT:PSS and the gelation time affected the organogel ?lm morphology of a nanostructure which is associated with their electrical properties. The resulting carbon-dot@PEDOT:PSS organogel ?lms were applied as an HTL for typical poly(3-hexylthiophene) (P3HT): [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) bulk heterojunction (BHJ) OPVs. As a result, the power conversion ef?ciency (PCE) of OPVs was enhanced by 30% due to the improvement of the electrical percolation pathway of the PEDOT:PSS ?lms.
关键词： PEDOT:PSS,Hole transport,Carbon-dots,Organic photovoltaics,Organogel
更新于2025-09-12 10:27:22
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Quinoidal Oligothiophenes Having Full Benzene Annelation: Synthesis, Properties, Structures, and Acceptor Application in Organic Photovoltaics
摘要： To achieve a complete closed-shell quinoidal state, bis(dicyanomethylene)-substituted quinoidal terthiophenes bearing benzene annelation at all thiophene rings were synthesized using a retro-Diels?Alder reaction as the key step. The unique structures and properties originating from the full benzene annelation were revealed by X-ray analysis as well as property measurements. Organic solar cells based on the combination of a donor polymer with a quinoidal terthiophene as an acceptor showed a power conversion e?ciency of 1.39%.
关键词： organic photovoltaics,retro-Diels?Alder reaction,non-fullerene acceptor,quinoidal oligothiophenes,benzene annelation
更新于2025-09-12 10:27:22
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Engineering Charge-Transfer States for Efficient, Low-Energy-Loss Organic Photovoltaics
摘要： Charge transfer (CT) between donors and acceptors following photoexcitation of organic photovoltaics (OPVs) gives rise to bound electron–hole pairs across the donor–acceptor interface, known as CT states. While these states are essential to charge separation, they are also a source of energy loss. As a result of reduced overlap between electron and hole wavefunctions, CT states are influenced by details of the film morphology and molecular structure. Here, we describe several important strategies for tuning the energy level and dynamics of the CT state and approaches that can enhance their dissociation efficiency into free charges. Furthermore, we provide an overview of recent physical insights into the key parameters that significantly reduce the Frenkel-to-CT energy offset and recombination energy losses while preserving a high charge-generation yield. Our analysis leads to critical morphological and molecular design strategies for achieving efficient, low-energy-loss OPVs.
关键词： molecular structure,energy loss,organic photovoltaics,charge transfer states,film morphology
更新于2025-09-12 10:27:22
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Perylene Diimide based Organic Photovoltaics with Slot-Die Coated Active Layers from Halogen-Free Solvents in Air at Room Temperature
摘要： Herein, we investigate the role of processing solvent additives on the formation of polymer-perylene diimide bulk-heterojunction active layers for organic photovoltaics using both spin-coating and slot-die coating methods. We compare the effect of 1,8-diiodooctane (DIO) and diphenyl ether (DPE) as solvent additives on the aggregation behavior of the non-fullerene acceptor tPDI2N-EH in neat films and blended films with the benzodithiophene-quinoxaline (BDT-QX, QX-3) donor polymer, processed from toluene in air. DIO-processing crystallizes the tPDI2N-EH acceptor and leads to decreased solar cell performance. DPE-processing has a more subtle effect on the bulk-heterojunction morphology and leads to improved solar cell performance. Comparing spin vs. slot-die coating methods, the effect of DPE is prominent for slot-die coated active layers. While similar device power conversion efficiencies are achieved with active layers coated with both methods (ca. 7.3% vs. 6.5%), the use of DPE improves film quality when the slot-die coating method is employed.
关键词： Organic photovoltaics,Halogen-free processing,Perylene diimide,Slot-die coating,Solvent additive,Diphenyl ether,Quinoxaline,Morphology control
更新于2025-09-12 10:27:22
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Potassium-Presenting Zinc Oxide Surfaces Induce Vertical Phase Separation in Fullerene-Free Organic Photovoltaics
摘要： Bulk heterojunction (BHJ) structure based organic photovoltaics (OPVs) have recently showed great potential for achieving high power conversion efficiencies (PCEs). An ideal BHJ structure would feature a large donor/acceptor interfacial area for efficient exciton dissociation and gradient distributions with high donor and acceptor concentrations near the anode and cathode, respectively, for efficient charge extraction. However, the random mixing of donor and acceptor in BHJ often suffers the severe charge recombination in the interface, resulting in poor charge extraction. Herein, we propose a new approach—treating the surface of the zinc oxide (ZnO) as electron transport layer with potassium hydroxide—to induce vertical phase separation of an active layer incorporating the non-fullerene acceptor IT-4F. Density functional theory calculations suggested that the binding energy difference between IT-4F and the PBDB-T-2Cl, to the potassium(K)-presenting ZnO interface is twice stronger than that for IT-4F and PBDB-T-2Cl to the untreated ZnO surface, such that it would induce more IT-4F moving toward the K-presenting ZnO interface than the untreated ZnO interface thermodynamically. Benefiting from efficient charge extraction, the best PCEs increased to 12.8% from 11.8% for PBDB-T-2Cl:IT-4F based devices, to 12.6% from 11.6% for PBDB-T-2Cl:Y1-4F based devices, to 13.5% from 12.2% for PBDB-T-2Cl:Y6 based devices, and to 15.7% from 15.1% for PM6:Y6 based devices.
关键词： DFT calculation,organic photovoltaics,potassium,vertical phase separation,non-fullerene acceptors
更新于2025-09-12 10:27:22
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Atom-Varied Side Chains in Conjugated Polymers Affect Efficiencies of Photovoltaic Devices Incorporating Small Molecules
摘要： We synthesized three conjugated polymers involving sulfur(S)-inserted and chlorine(Cl)-substituted side chains of the parent two-dimensional conjugated polymer—poly(benzodithiophene-thiophene-benzooxadiazole) (BO)—to form S-inserted (BO2S), Cl-substituted (BO2Cl) and S-inserted with Cl-substituted (BO2S2Cl) polymers for tuning their surface energies and, thus, interaction with IT-4F small molecule in their binary blends. In the BO:IT-4F blend, the bulk heterojunction (BHJ) structure was constituted mainly from the long-rod BO domains along with a few IT-4F domains that dispersed well in the blend; in contrast, favorable networks for charge transport existed in the BO2S or BO2S2Cl with IT-4F blend. The disk sizes of IT-4F in the BO2S2Cl:IT-4F blend were larger than that in the BO2S:IT-4F blend (23.3 vs. 18.1 nm). As the extent of atom variation increased from BO to BO2S to BO2S2Cl, the induced IT-4F crystallinity increased, and the orientation of molecular packing of the polymer varied. The highest PCE (12.06%) was that for the device based on the double sulfur-inserted/chlorine-substituted side chain polymer and IT-4F acceptor (BO2S2Cl:IT-4F), owing to the more balanced hole-to-electron mobility, being consistent with the value predicted (11.8%) using the random forest machine learning model. This study not only provides insight into the photovoltaic performance of the polymers with atom-inserted or -substituted side chain but also reveals that the effects of molecular packing.
关键词： organic photovoltaics,small molecule acceptor,machine learning,packing orientation,atom-varied polymer side chain
更新于2025-09-12 10:27:22
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Use of the Phen‐NaDPO:Sn(SCN) <sub/>2</sub> Blend as Electron Transport Layer Results to Consistent Efficiency Improvements in Organic and Hybrid Perovskite Solar Cells
摘要： A simple approach that enables a consistent enhancement of the electron extracting properties of the widely used small-molecule Phen-NaDPO and its application in organic solar cells (OSCs) is reported. It is shown that addition of minute amounts of the inorganic molecule Sn(SCN)2 into Phen-NaDPO improves both the electron transport and its film-forming properties. Use of Phen-NaDPO:Sn(SCN)2 blend as the electron transport layer (ETL) in binary PM6:IT-4F OSCs leads to a remarkable increase in the cells’ power conversion efficiency (PCE) from 12.6% (Phen-NaDPO) to 13.5% (Phen-NaDPO:Sn(SCN)2). Combining the hybrid ETL with the best-in-class organic ternary PM6:Y6:PC70BM systems results to a similarly remarkable PCE increase from 14.2% (Phen-NaDPO) to 15.6% (Phen-NaDPO:Sn(SCN)2). The consistent PCE enhancement is attributed to reduced trap-assisted carrier recombination at the bulk-heterojunction/ETL interface due to the presence of new energy states formed upon chemical interaction of Phen-NaDPO with Sn(SCN)2. The versatility of this hybrid ETL is further demonstrated with its application in perovskite solar cells for which an increase in the PCE from 16.6% to 18.2% is also demonstrated.
关键词： electron transporting layers,organic photovoltaics,Phen-NaDPO,nonfullerene acceptors,tin (II) thiocyanate
更新于2025-09-11 14:15:04
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Efficient Polymer Solar Cells Based on New Random Copolymers with Porphyrin‐Incorporated Side Chains
摘要： Two new wide bandgap block copolymers (PL1 and PL2) with porphyrin-incorporated side chains are designed and used as electron donors for solution-processed bulk heterojunction polymer solar cells. The photophysical, electrochemical, and photovoltaic properties, charge transport mobility and film morphology of these two block copolymers are investigated. Detailed investigations reveal that the different alkyl groups and electron-withdrawing substituents on the porphyrin pendant units have significant influence on the polymer solubility, absorption energy level, band gap, and charge separation in the bulk-heterojunction thin films, and thus the overall photovoltaic performances. Organic photovoltaic devices derived from these copolymers and ([6,6]-phenyl-C71-butyric acid methyl ester) (PC71BM) acceptor show the best power conversion efficiencies of 5.83% and 7.14%, respectively. These results show that the inclusion of a certain proportion of side chain porphyrin group as a pendant in the traditional donor-acceptor (D-A) type polymer can broaden the molecular absorption range and become a full-color absorbing molecule. The size of the porphyrin pendant also has an obvious effect on the properties of the molecule.
关键词： block copolymers,organic photovoltaics,polymer solar cells,bulk heterojunctions,porphyrin
更新于2025-09-11 14:15:04