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Improving open-circuit voltage by a chlorinated polymer donor endows binary organic solar cells efficiencies over 17%
摘要： Power conversion efficiency (PCE) of single-junction polymer solar cells (PSCs) has made a remarkable breakthrough recently. Plenty of work was reported to achieve PCEs higher than 16% derived from the PM6:Y6 binary system. To further increase the PCEs of binary OSCs incorporating small molecular acceptor (SMA) Y6, we substituted PM6 with PM7 due to the deeper highest occupied molecular orbital (HOMO) of PM7. Consequently, the PM7:Y6 has achieved PCEs as high as 17.0% by the hot-cast method, due to the improved open-circuit voltage (VOC). Compared with PM6, the lower HOMO of PM7 increases the gap between ELUMO-donor and EHOMO-acceptor, which is proportional to VOC. This research provides a high PCE for single-junction binary PSCs, which is meaningful for device fabrication related to PM7 and commercialization of PSCs.
关键词： binary system,power conversion efficiencies,open-circuit voltage,single junction
更新于2025-09-23 15:19:57
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Efficient Exciton Dissociation Enabled by the End Group Modification in Non-Fullerene Acceptors
摘要： For organic photovoltaic (OPV) cells, in order to overcome the larger Coulombic binding energy between holes and electrons, an extra driving force is required for efficient exciton dissociation. Here, we report two non-fullerene acceptors named IO-4H and IO-4F for OPV cells. By employing the polymer PBDB-TF as a donor, PBDB-TF:IO-4H-based device only shows a power conversion efficiency (PCE) of 0.30% with a charge dissociation probability (Pdiss) of 13.3%. On the contrary, PBDB-TF:IO-4F-based device demonstrates a PCE of 7.85%, with a Pdiss of 81.3%. The photoelectric processes demonstrate that both devices have similar charge transport and charge recombination properties. The limitation of photovoltaic performance is the low exciton dissociation efficiency in the PBDB-TF:IO-4H-based device. The theoretical studies show the electrostatic potential (ESP) of IO-4H is negative in the end groups and similar to the ESP of PBDB-TF, while ESP of IO-4F is positive. PBDB-TF and the IO-4F may form a strong intermolecular electric field to assist the exciton dissociation. Our results suggest that increasing the ESP difference between donor and acceptor may be beneficial to promote exciton dissociation, thus improving photovoltaic performance.
关键词： organic photovoltaic,electrostatic potential,power conversion efficiency,exciton dissociation,non-fullerene acceptors
更新于2025-09-23 15:19:57
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Inorganic molecule-induced electron transfer complex for highly efficient organic solar cells
摘要： Interfacial engineering of electrode modification has been proved to be an effective approach for improving the power conversion efficiency (PCE) of organic solar cells (OSCs). However, compared to the advance in active layer, the study of interfacial modification is seriously lagging behind and the contribution of electrode modification to the PCE enhancement is marginalized. Herein, we synthesized a series of polynuclear metal-oxo clusters (PMCs) with gradually varied chemical composition and photoelectronic properties, by which an efficient and stable hole extraction layer was developed to enhance OSC efficiencies. The PCE of the OSC modified by PMC-4 was improved from 15.7% to 16.3% as compared to the PEDOT:PSS device. Moreover, PMC-4 can be fabricated through solution processing without any post-treatment, and the corresponding device shows improved long-term stability. As revealed for the first time, the strong oxidizing property of PMC can induce the formation of inorganic-organic electron transfer complex with a barrier-free interface for efficient hole extraction. Furthermore, experimental data and theoretical calculation results reveal that the molecular polarization of mixed-addenda PMCs can enhance the capacitance at the AIL/active layer interfaces. As a result, the mixed-addenda PMCs can be processed by blade-coating to make a large-area OSC of 1 cm2, and a certified PCE of 14.3% was achieved.
关键词： power conversion efficiency,hole extraction layer,polynuclear metal-oxo clusters,organic solar cells,interfacial engineering
更新于2025-09-23 15:19:57
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Higher open circuit voltage caused by chlorinated polymers endows improved efficiency of binary organic solar cell
摘要： Organic solar cell (OSC) has achieved great progress in the past few years. Power conversion efficiency (PCE) has stepped into a new stage due to the evolution of non-fullerene acceptors (NFAs). The gap between lowest unoccupied molecular orbit of acceptor and highest occupied molecular orbit of donor (|ELUMOA-EHOMOD|) is proportional to the value of open circuit voltage (VOC). Applying two similar polymeric donors with different energy levels offers possibility of changing VOC without significantly impacting short circuit current (JSC) and fill factor (FF). Here we chose halogenated polymers PM6 and PM7 as donors to cope with a newly design asymmetric molecule TPIC-4Cl derived from IT-4Cl. As a result, the PM7:TPIC-4Cl device achieved a PCE of 15.1% than its PM6:TPIC-4Cl counterparts (14.4%), wherein the improvement of VOC from 0.855V to 0.885V contributed most. Our work proves the feasibility of improving photovoltaic performance of NFA OSCs by utilizing polymeric donors with similar structure yet different HOMOs. Besides, the PCE over 15% of OSCs involving no Y6 or its derivatives sheds light on another direction of OSC research.
关键词： gap tuning,power conversion efficiency,non-fullerene acceptor
更新于2025-09-23 15:19:57
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Design and Synthesis of Non-Fullerene Acceptors Based on Quinoxalineimide Moiety as the Central Building Block for Organic Solar Cells
摘要： Two new non-fullerene acceptors, namely QIP-4F and QIP-4Cl, contain a novel imide-functionalized quinoxaline (QI) moiety fused with thienylthiophene unit as the central building block, and chlorinated or fluorinated 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile as end-capping groups, were designed and synthesized, respectively. An optimized device based on P2F-EHp:QIP-4Cl presented a power conversion efficiency of 13.3%, with an impressively high open-circuit voltage of 0.94 V. The results demonstrate the great potential of QI-containing fused units as central building blocks for high-performance acceptors.
关键词： quinoxalineimide,organic solar cells,power conversion efficiency,non-fullerene acceptors
更新于2025-09-23 15:19:57
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Charge-transport layer engineering in perovskite solar cells
摘要： Photovoltaic (PV) technology that directly converts the solar energy into electrical energy, is regarding as one of the most promising utilization technologies of renewable and clean energy sources. Nowadays, developing low-cost and highly efficient PV technology is a hot research topic both for academia and industry. In this context, perovskite solar cells (PSCs) with metal halide perovskites [ABX3, A = CH3NH3+ (MA+), or CH(NH2)2+ (FA+), Cs+; B = Pb2+, Sn2+; X = Cl?, Br?, I?] as light harvesting material, is in the spotlight due to its easy fabrication process and high power conversion efficiency (PCE) [1,2]. To date, the certified PCE has been already pushed up to 25.2% (https://www.nrel.gov/pv/module-efficiency.html), making PSC an auspicious candidate for a new generation of photovoltaics. In future days, how to eliminate the non-essential charge carrier recombination in the device, further push the PCE approaching the Shockley-Queisser theoretical efficiency limit (~35%) and enhance the device stability, will be formidable challenges and the focus in the next stage of research work.
关键词： electron transport layer,hole transport layer,charge-transport layer,perovskite solar cells,power conversion efficiency
更新于2025-09-23 15:19:57
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A Trifluoromethyl Group Modified Non-fullerene Acceptor Towards Improved Power Conversion Efficiency Over 13% in Polymer Solar Cells
摘要： Herein, we report a new molecule structure modification strategy for non-fullerene small molecule electron acceptors (NFAs) for solar cells through trifluoromethylation of end-capping groups. The synthesized trifluoromethylated acceptor ITCF3 exhibits narrower band gap, stronger light absorption, lower molecular energy levels and better electron transport property comparing to the reference NFA without trifluoromethyl group (ITIC). Bulk heterojunction solar cells based on ITCF3 combined with PM6 polymer donor exhibit a significantly improved power conversion efficiency of 13.3% comparing with ITIC-based device (8.4%). This work reveals great potential of trifluoromethylation in design of efficient photovoltaic acceptor materials.
关键词： power conversion efficiency,non-fullerene acceptor,trifluoromethyl group,organic solar cell,polymer
更新于2025-09-23 15:19:57
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Enhanced Photovoltaic Performance by Synergistic Effect of Chlorination and Selenophene ??-Bridge
摘要： In the rapid innovation of organic solar cells, polymer donor plays a significant role in achieving high power conversion efficiencies (PCEs). The strong intermolecular interactions and deep highest occupied molecular orbitals (HOMOs) of donor polymers will facilitate the favorable phase separation and high open-circuit voltage (Voc), resulting in the dramatic improvement of device performance. Herein, combined chlorination of 4,8-bis(thiophene-2-yl)-benzo[1,2-b:4,5-b′]-dithiophene (T-BDT) and selenophene π-bridges, a new polymer donor, named PBBSe-Cl, is designed and synthesized. Compared to its parent polymer without chlorine substitution and π-bridge (named PBB), PBBSe-Cl exhibits much stronger absorption, better molecular planarity, and improved molecular aggregations. Moreover, PBBSe-Cl shows favorable phase separation and bicontinuous interpenetrating network when blending with acceptor Y6. As a result, the inverted device based on PBBSe-Cl achieves a decent PCE of 14.44%, with synchronously improved short-circuit current density (Jsc) of 24.07 mA cm?2 and fill factor (FF) of 73.16%. However, its parent polymers PBB and PBBSe-H only present a relatively low device performance. In addition, a very low energy loss (Eloss) of 0.51 eV is realized for PBBSe-Cl-based devices. This investigation proves that introducing chlorine atoms on the conjugated side chains and selenophene π-bridges will stepwise increase the polymer solar cell efficiency due to the simultaneous enhancement of device current density and fill factor. The proper usage of chlorination and selenophene π-bridge is a facile and efficient strategy for high-performance solar conversion materials.
关键词： selenophene π-bridges,organic solar cells,power conversion efficiencies,chlorination,polymer donor
更新于2025-09-23 15:19:57
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Optimized Molecular Packing and Nonradiative Energy Loss Based on Terpolymer Methodology Combining Two Asymmetric Segments for High-Performance Polymer Solar Cells
摘要： In this work, a random terpolymer methodology combining two electron-rich units, asymmetric thienobenzodithiophene (TBD) and thieno[2,3-f]benzofuran (TBF) segments, is systematically investigated. The synergetic effect is embodied on the molecular packing and nanophase when copolymerization with 1,3-bis(2-ethylhexyl)benzo[1,2-c:4,5-c']dithiophene-4,8-dione (BDD), producing an impressive power conversion efficiency (PCE) of 14.2% in IT-4F based NF-PSCs, which outperformed the corresponding D-A copolymers. The balanced aggregation and better interpenetrating network of the TBD50:IT-4F blend film can lead to mixing region exciton splitting and suppress carrier recombination, along with high yields of long-lived carriers. Moreover, the broad applicability of terpolymer methodology is successfully validated in most electron-deficient systems. Especially, TBD50/Y6-based device exhibits high PCE of 15.0% with a small energy loss (0.52 eV) enabled by the low non-radiative energy loss (0.22 eV), which are among the best values reported for polymers without using BDT unit to date. These results demonstrate an outstanding terpolymer approach with backbone engineering to raise the hope of achieving even higher PCEs and to enrich organic photovoltaic materials reservoir.
关键词： asymmetrical structure,microstructure,random terpolymer,nonfullerene solar cell,non-radiative energy loss,power conversion efficiency
更新于2025-09-23 15:19:57
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Delocalization boosts charge separation in organic solar cells
摘要： Organic solar cells (OSCs) utilizing π-conjugated polymers have attracted widespread interest over the past three decades because of their potential advantages, including low weight, thin film flexibility, and low-cost manufacturing. However, their power conversion efficiency (PCE) has been far below that of inorganic analogs. Geminate recombination of charge transfer excitons is a major loss process in OSCs. This paper reviews our recent progress in using transient absorption spectroscopy to understand geminate recombination in bulk heterojunction OSCs, including the impact of polymer crystallinity on charge generation and dissociation mechanisms in nonfullerene acceptor-based OSCs. The first example of a high PCE with a small photon energy loss is also presented. The importance of delocalization of the charge wave function to suppress geminate recombination is highlighted by this focus review.
关键词： Polymer crystallinity,Power conversion efficiency,Organic solar cells,Transient absorption spectroscopy,Dissociation mechanisms,Photon energy loss,π-conjugated polymers,Charge generation,Nonfullerene acceptor,Geminate recombination
更新于2025-09-23 15:19:57