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Constructing Higha??Performance Organic Photovoltaics via Emerging Nona??Fullerene Acceptors and Tandema??Junction Structure
摘要： In consideration of the unique advantages of new non-fullerene acceptors and the tandem-junction structure, organic photovoltaics (OPVs) based on them are very promising. Studies related to this emerging area began in 2016 with achieved power conversion efficiencies (PCEs) of 8–10%, which have now been boosted to 17%. In this essay, the construction of high-performance OPVs is discussed, with a focus on combining the advantages of new non-fullerene acceptors and the tandem-junction structure. In order to achieve higher PCEs, methods to enable high short-circuit current density, open-circuit voltage, and fill factor are discussed. In addition, the stability and reproducibility of high-efficiency OPVs are also addressed. Herein, it is forecast that the new non-fullerene acceptors-based tandem-junction OPVs will become the next big wave in the field and achieve high PCEs over 20% in the near future. Some promising research directions on this emerging hot topic are proposed which may further push the field into the 25% high efficiency era and considerably advance the technology beyond laboratory research.
关键词： non-fullerene acceptors,organic solar cells,organic photovoltaics,tandem solar cells
更新于2025-09-23 15:19:57
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Organic Photovoltaics: Relating Chemical Structure, Local Morphology, and Electronic Properties
摘要： Substantial enhancements in the efficiencies of bulk-heterojunction (BHJ) organic solar cells (OSCs) have come from largely trial-and-error-based optimizations of the morphology of the active layers. Further improvements, however, require a detailed understanding of the relationships among chemical structure, morphology, electronic properties, and device performance. On the experimental side, characterization of the local (i.e., nanoscale) morphology remains challenging, which has called for the development of robust computational methodologies that can reliably address those aspects. In this review, we describe how a methodology that combines all-atom molecular dynamics (AA-MD) simulations with density functional theory (DFT) calculations allows the establishment of chemical structure–local morphology–electronic properties relationships. We also provide a brief overview of coarse-graining methods in an effort to bridge local to global (i.e., mesoscale to microscale) morphology. Finally, we give a few examples of machine learning (ML) applications that can assist in the discovery of these relationships.
关键词： Machine Learning,Density Functional Theory,Organic Photovoltaics,Organic Solar Cells,Bulk-Heterojunction,Electronic Properties,Coarse-Graining Methods,Local Morphology,Chemical Structure,All-Atom Molecular Dynamics
更新于2025-09-23 15:19:57
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Modifications of ZnO Interlayer to Improve the Power Conversion Efficiency of Organic Photovoltaic Cells
摘要： Power conversion efficiency (PCE) is an important parameter in determining the performance of organic photovoltaics (OPVs). Various factors lead to enhancement of power conversion efficiency. One such factor is doping of electron transport layer. A substantial increase in the power conversion efficiency of inverted organic solar cells is realized by a ZnO doped buffer layer acting as an electron-transport layer. Different works on Li, Cd, Ga, Al doping, introduction of C60 interface layer in ZnO buffer layer and dual doped system of InZnO-BisC60 have been reviewed here. The Al-doped buffer layer device showed the highest increase in power conversion efficiency.
关键词： Power conversion efficiency,Organic photovoltaics,ZnO interlayer,Doping
更新于2025-09-23 15:19:57
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Alkyl Side-Chain Dependent Self-Organization of Small Molecule and its Application in High-Performance Organic and Perovskite Solar Cells
摘要： The molecular self-organization of organic semiconductors, which is mainly determined by the structural design, film processing, and device configuration, is one of the crucial factors for achieving high-performance organic photovoltaics (OPVs) and perovskite solar cells (PvSCs). In this study, we newly synthesized and developed strongly self-organized small molecules via alkyl side-chain engineering. Replacing “H” to “C6H13” on the thienyl group, SM2 showed a well-ordered face-on orientation. Due to favorable self-organization leading to effective charge carrier dynamics, including enhanced charge transfer/transport and suppressed recombination, SM2-based OPVs and PvSCs exhibited improved device performance compared to the devices based on SM1 without an additional hexyl side-chain. The best fullerene-based OPV and planar PvSC with SM2 as a small-molecule donor and as a hole transport layer (HTL) achieved an unprecedentedly high efficiency of 9.38% and 20.56%, in contrast with SM1-based devices showing lower efficiency of 8.70% and 15.37%. Furthermore, the planar PvSCs based on undoped-SM2 HTL exhibited comparable efficiency but provided excellent heat and humidity stability compared with doped spiro-OMeTAD-based devices. These results clearly indicated that SM2 with highly-ordered and favorable self-organization is a promising organic semiconductor for future applications of high-performance organic and inorganic-organic hybrid electronics.
关键词： small molecule,organic photovoltaics,alkyl side-chain,self-organization,perovskite solar cells
更新于2025-09-23 15:19:57
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The Phase Behavior in the Active Layer of Small Molecule Organic Photovoltaics: The State Diagram of p-DTS(FBTTh <sub/>2</sub> ) <sub/>2</sub> :PC <sub/>71</sub> BM
摘要： A comprehensive study was undertaken to obtain a more fundamental understanding of the phase behavior of the p-DTS(FBTTh2)2:PC71BM system, used in small molecule organic solar cells, with a strong focus on the amorphous phase and its influence on crystallinity. Three dedicated thermal protocols were used in combination with advanced thermal analysis, solid-state NMR, and wide angle X-ray diffraction. Rapid cooling, to avoid structure formation and gain insight in the amorphous phase, and slow cooling, to promote structure formation, were used as limiting cases to explain the intermediate behavior after device processing from solution. A complete state diagram was developed and the glass transition (Tg) - composition relationship was determined. In the case of slow cooling and the procedure used for device processing, the rapid crystallization of p-DTS(FBTTh2)2 leads to an enrichment of the amorphous phase in PC71BM, increasing its Tg and causing vitrification of the mixed amorphous phase before crystallization when the total amount of PC71BM exceeds 70 wt%. The common processing additive 1,8-diiodooctane (DIO) was found to lead to a lower p-DTS(FBTTh2)2 crystallinity and smaller average crystal size. More importantly, it acts as a strong plasticizer, lowering Tg significantly and thus reducing the morphological stability of the p-DTS(FBTTh2)2:PC71BM mixtures.
关键词： p-DTS(FBTTh2)2:PC71BM,glass transition temperature,wide angle X-ray diffraction,phase behavior,crystallinity,amorphous phase,small molecule organic photovoltaics,thermal analysis,solid-state NMR,1,8-diiodooctane (DIO)
更新于2025-09-23 15:19:57
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Barrier-Free Charge Separation Enabled by Electronic Polarization in High-Efficiency Non-Fullerene Organic Solar Cells
摘要： The separation of charge-transfer (CT) states into free charges at the donor/acceptor (D/A) interfaces plays a central role for organic solar cells (OSCs). Because of strong Coulomb attraction, the separation mechanisms are elusive, particularly for the high-efficiency non-fullerene (NF) OSCs with low exciton-dissociation driving forces. Here, we demonstrate that the Coulomb barriers can be substantially overcome by electronic polarization for OSCs based on a series of A-D-A acceptors (ITIC, IT-4F, and Y6). In contrast to fullerene-based D/A heterojunctions, the polarization energies for both donor holes and acceptor electrons are remarkably increased from the interfaces to pure regions in the NF heterojunctions owing to strong stabilization on electrons but destabilization on holes by electrostatic interactions in the A-D-A acceptors. Especially, upon incorporating fluorine substituents and electron-poor cores to ITIC, the increased polarization energies can completely compensate the Coulomb attraction in the IT-4F and Y6 based Heterojunctions, leading to barrierless charge separation.
关键词： electrostatic interaction,induction effect,charge generation,organic photovoltaics,non-fullerene acceptors
更新于2025-09-23 15:19:57
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Quantification of Photophysical Processes in Alla??Polymer Bulk Heterojunction Solar Cells
摘要： Combined data of transient optical and electro-optical experiments reveals the efficiency-determining processes in all-polymer solar cells and allows precisely quantifying their yields. For the test system presented here, field-dependent charge separation is shown to limit the fill factor and thus the performance by comparing the experimentally-measured current-voltage characteristics to those reproduced by drift-diffusion simulations using the spectroscopically-determined kinetic parameters.
关键词： all-polymer solar cells,bulk heterojunction,non-fullerene acceptors,transient absorption,organic photovoltaics
更新于2025-09-23 15:19:57
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Dithiazolylthienothiophene Bisimide-Based ??-Conjugated Polymers: Improved Synthesis and Application to Organic Photovoltaics as P-Type Semiconductor
摘要： Dithiazolylthienothiophene bisimide (TzBI) is a promising building unit for donor-acceptor π-conjugated polymers due to its strong electron-deficiency and high coplanarity. We previously reported a TzBI-based π-conjugated polymer functioned as n-type semiconductor in organic photovoltaic cells. However, a critical subject was that the molecular weight of the polymer was not sufficiently high. It is also important to investigate the possibility of TzBI-based polymers as the p-type semiconductor. In this study, we show that a new synthetic approach gave a new TzBI-based polymer with an improved molecular weight relative to the previously reported polymer. Further, having a co-building unit with a more electron-rich nature, the polymer functioned as p-type semiconductor in organic photovoltaic cells when the PC61BM was used as n-type material. This study shows that TzBI is a versatile building unit for π-conjugated polymers that can be used in organic electronic devices.
关键词： Imide,π-Conjugated polymers,Organic photovoltaics
更新于2025-09-23 15:19:57
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High indoor performance of flexible organic photovoltaics using polymer electrodes
摘要： Indoor organic photovoltaics (OPVs) have gained tremendous attention due to their unique optoelectronic properties under dim and spectrally-limited indoor light conditions. Moreover, their excellent flexible features make them more suitable for powering various indoor electronic devices than other photovoltaic systems. In this article, we demonstrate the indoor photovoltaic performance of poly(3-hexylthiophene):indene-C60 bisadduct-based flexible OPVs with polymeric electrodes in comparison with reference OPVs with indium tin oxide (ITO) electrodes. For the flexible OPVs, poly (3, 4-ethylenedioxythiophene): poly (styrene-sulfonic acid)-based polymeric electrodes were demonstrated on a polyethylene naphthalate substrate with a polyvinyl alcohol buffer layer. The OPV with the polymeric electrode produced an average power conversion efficiency (PCE) of 11.1 ± 0.1%, whereas the reference device with the ITO electrode exhibited a PCE of 8.8 ± 0.1% under a 500-lx-light emitting diode condition. The flexible OPVs also exhibited superior flexibility over reference OPVs by retaining their PCE up to ~ 85% even after 500 bending cycles in air, whereas the reference OPVs declined to ~ 80% of their PCE under the same bending conditions.
关键词： Organic photovoltaics,Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate,Polymeric electrode,Indoor application,Parasitic resistance effects
更新于2025-09-23 15:19:57
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Thienyl Sidechain Substitution and Backbone Fluorination of Benzodithiophene-Based Donor Polymers Concertedly Minimize Carrier Losses in ITIC-Based Organic Solar Cells
摘要： Non-fullerene acceptor (NFA) based organic solar cells have outperformed fullerene-based devices, yet their photophysics is less well understood. Herein, changes in the donor polymer backbone side-chain substitution and backbone fluorination in benzodithiophene (BDT)-thiophene copolymers are linked to the photophysical processes and performance of bulk heterojunction (BHJ) solar cells, using ITIC as NFA. Increased geminate recombination is observed when the donor polymer is alkoxy-substituted in conjunction with faster non-geminate recombination of free charges, limiting both the short circuit current and device fill factor. In contrast, thienyl-substitution reduces geminate recombination, albeit non-geminate recombination remains significant, leading to improved short circuit current density, yet not fill factor. Only the combination of thienyl-substitution and polymer backbone fluorination yields both efficient charge separation and significantly reduced non-geminate recombination, resulting in fill factors (FFs) in excess of 60 %. Time-delayed collection field measurements ascertain that charge generation is field-independent in the thienyl-substituted donor polymer:ITIC systems, while weakly field dependent in the alkoxy-substitued polymer:ITIC blend, indicating the low FFs are primarily caused by non-geminate recombination. This work provides insight into the interplay of donor polymer structure, BHJ photophysics, and device performance for a prototypical NFA, namely ITIC. More specifically, it links the donor polymer chemical structure to quantifiable changes of kinetic parameters and the yield of individual processes in ITIC-based BHJ blends.
关键词： non-fullerene acceptor,ultrafast spectroscopy,bulk heterojunction,charge generation,organic photovoltaics
更新于2025-09-23 15:19:57