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Charge Density Modulation on Asymmetric Fused-Ring Acceptors for High-Efficiency Photovoltaic Solar Cells
摘要： Charge density modulation on thieno[2'',3'':5',6']-s-indaceno[2',1':4,5]dithieno[3,2-b:2’,3’-d]pyrrole (IPT) core has been conducted for a systematic study of its impact on the electronic structure, molecular packing and photovoltaic performance of asymmetric fused-ring acceptors (FRAs). Herein, a series of IPT-based FRAs (ca. IN-4F, INO-4F, IPT-4F and IPCl-4F) are designed by adopting a corresponding side-chain of 2-ethylhexyl, 2-ethylhexyloxy, hydrogen or chloro onto IPT core. Enhanced electron-withdrawing side-chains contract the optical bandgap but lower the lowest unoccupied molecular orbital (LUMO) level, which yields a trade-off between JSC and VOC in organic solar cells (OSCs). Furthermore, the FRAs exhibit tuned miscibility and crystallinity, reflected on the FF and JSC values of the OSCs. By pairing with polymer donor PM6, IPT-4F based devices achieve the highest PCE of 14.62% with balanced VOC of 0.88 V and JSC of 22.15 mA cm-2 and high FF of 75.01%. Our research demonstrates that electronic density modulation on asymmetric FRAs is an effective way to systematically optimize the device parameters in pursuit of high performance OSCs.
关键词： asymmetric fused-ring acceptors,Charge density modulation,electron-withdrawing side-chains,organic solar cells,photovoltaic performance
更新于2025-09-23 15:21:01
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Over 15.7% Efficiency of Ternary Organic Solar Cells by Employing Two Compatible Acceptors with Similar LUMO Levels
摘要： Efficient organic solar cells (OSCs) are fabricated using polymer PM6 as donor, and IPTBO-4Cl and MF1 as acceptors. The power conversion efficiency (PCE) of IPTBO-4Cl based and MF1 based binary OSCs individually arrive to 14.94% and 12.07%, exhibiting markedly different short circuit current density (JSC) of 23.18 mA cm?2 versus 17.01 mA cm?2, fill factor (FF) of 72.17% versus 78.18% and similar open circuit voltage (VOC) of 0.893 V versus 0.908 V. The two acceptors, IPTBO-4Cl and MF1, have similar lowest unoccupied molecular orbital levels, which is beneficial for efficient electron transport in the ternary active layer. The PCE of optimized ternary OSCs arrives to 15.74% by incorporating 30 wt% MF1 in acceptors, resulting from the simultaneously increased JSC of 23.20 mA cm?2, VOC of 0.897 V, and FF of 75.64% in comparison with IPTBO-4Cl based binary OSCs. The gradually increased FFs of ternary OSCs indicate the well-optimized phase separation and molecular arrangement with MF1 as morphology regulator. This work may provide a new viewpoint for selecting an appropriate third component to achieve efficient ternary OSCs from materials and photovoltaic parameters of two binary OSCs.
关键词： organic solar cells,morphology regulators,compatible acceptors,ternary strategy
更新于2025-09-23 15:21:01
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Exploiting ternary blends for improved photostability in high efficiency organic solar cells
摘要： Ternary organic solar cells based on polymer donor and nonfullerene acceptors (NFAs) are delivering high power conversion efficiencies (PCE). Now, further improvement needs to be directed to enhance the operational lifetime of organic photovoltaics. Here, we selected three NFAs with different electron affinities and structural properties and found that the most crystalline third component, O-IDTBR, is selectively miscible within the acceptor phase. This reduced trap-assisted recombination and delivered a PCE of 16.6% and a fill factor of 0.76, compared to PM6:Y6 binary devices (15.2% PCE). Charge transport and recombination analyses revealed that O-IDTBR acts as a charge relay for improved charge transfer of both donor and acceptor materials leading to a more ordered transport. We find that minimizing traps formation in ternary devices deactivates light-induced traps upon full sun illumination (AM1.5G). As a result, ternary devices do not show any PCE drop in 225h, in comparison to binary cells which lose more than 60% of their initial performances.
关键词： photostability,nonfullerene acceptors,ternary organic solar cells,power conversion efficiency,charge transport
更新于2025-09-23 15:21:01
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Structure-Property Study of Homoleptic Zinc(II) Complexes of Di(arylethynyl) Azadipyrromethene as Non-Fullerene Acceptors for Organic Photovoltaics: Effect of Aryl Group
摘要： Azadipyrromethene-based zinc(II) complexes were demonstrated to be promising molecular organic semiconductors for electronic applications due to their easy preparation, tunable structures and high electron affinity. The first successful such complex incorporated phenylethynyl groups at the pyrrolic positions, which red-shifted the absorption spectra of zinc(II) bis(tetraphenyl azadipyrromethene) and improved morphology in blends with poly(3-hexylthiophene) (P3HT). We recently discovered that replacing the phenyl group in the pyrrolic positions with the larger 1-naphthyl group [Zn(L2)2] increases crystallinity and improves the organic photovoltaic (OPV) performance. In this work, two more aryl groups were explored to further investigate the relationship between the aryl groups in the pyrrolic position and electronic properties: naphthyl with a different anchoring site, 2-naphthyl [Zn(L3)2], and a larger aryl group, 9-phenanthrenyl [Zn(L4)2]. The larger aryl group slightly improved absorptivity and red-shifted the absorption spectra and lead to different packing modes in crystals with most intermolecular π-π stacking interactions being of T-shaped type involving the pyrrolic aryl group of one complex. Of the series, 1-naphthyl gave the highest crystallinity. The OPV power conversion efficiency (PCE) of Zn(L3)2 and Zn(L4)2 when blended with P3HT was 3.7% and 3.4%, respectively, both lower than that of Zn(L2)2, PCE of 5.5% due to higher trap-assisted recombination and less favorable morphology. Charge carrier mobility in these complexes was also relatively low, also limiting performance. Single-point energy calculations point to low overlap integrals as a cause for the low mobility. The aryl group anchoring position and size therefore have a large effect on properties in these systems, but do not appear to significantly enhance intermolecular interactions.
关键词： Azadipyrromethene,zinc(II) complexes,non-fullerene acceptors,structure-property study,organic photovoltaics
更新于2025-09-23 15:21:01
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Efficient and Stable Deep-Blue Fluorescent Organic Light-Emitting Diodes Employing a Sensitizer with Fast Triplet Upconversion
摘要： Multiple donor–acceptor-type carbazole–benzonitrile derivatives that exhibit thermally activated delayed fluorescence (TADF) are the state of the art in efficiency and stability in sky-blue organic light-emitting diodes. However, such a motif still suffers from low reverse intersystem crossing rates (kRISC) with emission peaks <470 nm. Here, a weak acceptor of cyanophenyl is adopted to replace the stronger cyano one to construct blue emitters with multiple donors and acceptors. Both linear donor–π–donor and acceptor–π–acceptor structures are observed to facilitate delocalized excited states for enhanced mixing between charge-transfer and locally excited states. Consequently, a high kRISC of 2.36 × 106 s?1 with an emission peak of 456 nm and a maximum external quantum efficiency of 22.8% is achieved. When utilizing this material to sensitize a blue multiple-resonance TADF emitter, the corresponding device simultaneously realizes a maximum external quantum efficiency of 32.5%, CIEy ≈ 0.12, a full width at half maximum of 29 nm, and a T80 (time to 80% of the initial luminance) of > 60 h at an initial luminance of 1000 cd m?2.
关键词： stable deep-blue devices,sensitized emission,high reverse intersystem crossing,thermally activated delayed fluorescence,multiple donors and acceptors
更新于2025-09-23 15:21:01
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Efficient charge generation at low energy losses in organic solar cells: a key issue review
摘要： Light absorption generates strongly bound excitons in organic solar cells (OSCs). To obtain efficient charge generation, a large driving force is required, which causes a large energy loss (Eloss) and severely hinders the improvement in the power conversion efficiencies (PCEs) of OSCs. Recently, the development of non-fullerene OSCs has seen great success, and the resulting OSCs can yield highly efficient charge generation with a negligible driving force, which raises a fundamental question about how the excitons split into free charges. From a chemical structure perspective, the molecular electrostatic potential differences between donors and acceptors may play a critical role in facilitating charge separation. Although the Eloss caused by charge generation has been suppressed, charge recombination, particularly via non-radiative pathways, severely limits further improvements in the PCEs. In OSCs with negligible driving forces, the lowest excited state, a hybrid local exciton-charge transfer state, is believed to have a strong association with the non-radiative Eloss. This review discusses the efficient charge generation at low Eloss values in highly efficient OSCs and highlights the issues that should be tackled to further improve the PCEs to new levels (~ 20%).
关键词： energy loss,organic solar cells,non-fullerene acceptors,electrostatic potential,charge generation
更新于2025-09-23 15:21:01
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Electrona??Deficient and Quinoid Central Unit Engineering for Unfused Ringa??Based A <sub/>1</sub> a??Da??A <sub/>2</sub> a??Da??A <sub/>1</sub> a??Type Acceptor Enables High Performance Nonfullerene Polymer Solar Cells with High <i>V</i> <sub/>oc</sub> and PCE Simultaneously
摘要： Here, a pair of A1–D–A2–D–A1 unfused ring core-based nonfullerene small molecule acceptors (NF-SMAs), BO2FIDT-4Cl and BT2FIDT-4Cl is synthesized, which possess the same terminals (A1) and indacenodithiophene unit (D), coupling with different fluorinated electron-deficient central unit (difluorobenzoxadiazole or difluorobenzothiadiazole) (A2). BT2FIDT-4Cl exhibits a slightly smaller optical bandgap of 1.56 eV, upshifted highest occupied molecular orbital energy levels, much higher electron mobility, and slightly enhanced molecular packing order in neat thin films than that of BO2FIDT-4Cl. The polymer solar cells (PSCs) based on BT2FIDT-4Cl:PM7 yield the best power conversion efficiency (PCE) of 12.5% with a Voc of 0.97 V, which is higher than that of BO2FIDT-4Cl-based devices (PCE of 10.4%). The results demonstrate that the subtle modification of A2 unit would result in lower trap-assisted recombination, more favorable morphology features, and more balanced electron and hole mobility in the PM7:BT2FIDT-4Cl blend films. It is worth mentioning that the PCE of 12.5% is the highest value in nonfused ring NF-SMA-based binary PSCs with high Voc over 0.90 V. These results suggest that appropriate modulation of the quinoid electron-deficient central unit is an effective approach to construct highly efficient unfused ring NF-SMAs to boost PCE and Voc simultaneously.
关键词： nonfullerene organic solar cells,unfused ring small molecular acceptors,polymer solar cells,electron-deficient central segment,difluorobenzothiadiazole
更新于2025-09-23 15:21:01
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Axisymmetric and Asymmetric Naphthalene-Bisthienothiophene Based Nonfullerene Acceptors: on Constitutional Isomerization and Photovoltaic Performance
摘要： Two pairs of constitutional isomers of fused-octacyclic nonfullerene acceptors (NFAs) based on a naphthalene-bisthienothiophene core with or without fluorination at the ending groups have been developed. Compared with the axisymmetric NFAs N66-IC and N66-2FIC with two six-member-ring bridges, their asymmetric constitutional isomers N65-IC and N65-2FIC both with one six-member-ring bridge and one five-member-ring bridge exhibit remarkable red-shifted absorption, higher crystallinity, and slightly down-shifted LUMO energy levels. Organic solar cells based on PBDB-T-2F:N65-2FIC achieved a promising power conversion efficiency of 10.19%, which is three times higher than that of its counterpart PBDB-T-2F:N66-2FIC cell (3.46%). While being blended with PBDB-T as the donor material, the asymmetric acceptor analogue N65-IC based solar cell pronounces a PCE of 9.03%, being significantly improved from that of 5.45% for the PBDB-T:N66-IC based cell, which is in consistency with the results from those cells from their both fluorinated donor and acceptor counterparts. Design rules on either both fluorinated, both non-fluorinated, or cross-combined donor/acceptors for device fabrication has been explored. In addition, PBDB-T-2F:N65-2FIC possesses very promising device stability with 85% of its initial PCE after an exposure time of 1500 h under one sun illumination, which is meaningful for their future commercial devices.
关键词： isomerization,naphthalene,organic solar cells,nonfullerene acceptors,asymmetry,axisymmetry
更新于2025-09-23 15:21:01
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Toward Efficient Triple-Junction Polymer Solar Cells through Rational Selection of Middle Cells
摘要： The photon energy losses of polymer solar cells (PSCs) routinely drag their experimental power conversion efficiencies (PCEs) far below the theoretical limits. We report herein efficient triple-junction PSCs (TJ-PSCs) with mitigated energy losses through rational selection of subcells. We reveal that avoiding strong photon competition between the front and middle cells is critical in balancing the absorption rate among subcells with realistic layer thicknesses. Efficient TJ-PSCs are achieved by stacking a front cell of PBDB-T-2F:PC71BM, a middle cell of PBDB-T:HF-TCIC, and a rear cell of PTB7-Th: IEICO-4F in series and connecting them with two functional interconnection layers. A PCE of 13.09% is obtained from champion devices, representing one of the best TJ-PSCs among the reported studies. It accounts for a 35% improvement in efficiency over those of single-junction PSCs with the same absorption range, which is mainly attributed to the reduced nonabsorbing and thermalization losses of TJ-PSCs.
关键词： polymer solar cells,photon energy losses,power conversion efficiencies,nonfullerene acceptors,triple-junction
更新于2025-09-23 15:21:01
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Perylene Diimide Based Conjugated Polymers for All Polymer Solar Cells
摘要： For recent decades, non-fullerene acceptors (NFAs) are undergoing rapid development and emerging as a hot area in the field of organic solar cells. Among the high performance nonfullerene acceptors, aromatic diimide based electron acceptors remain to be the highly promising systems. This review discusses the important progress of perylene diimide (PDI)-based polymers as nonfullerene acceptors (NFAs) in all polymer solar cells (all-PSCs) since 2014. The relationship between structure and property, matching aspects between donors and acceptors and device fabrications are unveiled from a synthetic chemist perspective.
关键词： nonfullerene acceptors (NFA),all-polymer solar cells (all-PSCs),energy levels,perylene diimide (PDI),PCE
更新于2025-09-23 15:21:01