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Asymmetric Electron Acceptors for Higha??Efficiency and Lowa??Energya??Loss Organic Photovoltaics
摘要： Low energy loss and efficient charge separation under small driving forces are the prerequisites for realizing high power conversion efficiency (PCE) in organic photovoltaics (OPVs). Here, a new molecular design of nonfullerene acceptors (NFAs) is proposed to address above two issues simultaneously by introducing asymmetric terminals. Two NFAs, BTP-S1 and BTP-S2, are constructed by introducing halogenated indandione (A1) and 3-dicyanomethylene-1-indanone (A2) as two different conjugated terminals on the central fused core (D), wherein they share the same backbone as well-known NFA Y6, but at different terminals. Such asymmetric NFAs with A1-D-A2 structure exhibit superior photovoltaic properties when blended with polymer donor PM6. Energy loss analysis reveals that asymmetric molecule BTP-S2 with six chlorine atoms attached at the terminals enables the corresponding devices to give an outstanding electroluminescence quantum efficiency of 2.3 × 10?2%, one order of magnitude higher than devices based on symmetric Y6 (4.4 × 10?3%), thus significantly lowering the nonradiative loss and energy loss of the corresponding devices. Besides, asymmetric BTP-S1 and BTP-S2 with multiple halogen atoms at the terminals exhibit fast hole transfer to the donor PM6. As a result, OPVs based on the PM6:BTP-S2 blend realize a PCE of 16.37%, higher than that (15.79%) of PM6:Y6-based OPVs. A further optimization of the ternary blend (PM6:Y6:BTP-S2) results in a best PCE of 17.43%, which is among the highest efficiencies for single-junction OPVs. This work provides an effective approach to simultaneously lower the energy loss and promote the charge separation of OPVs by molecular design strategy.
关键词： asymmetric acceptors,molecular design strategies,nonfullerene acceptors,charge separation,organic photovoltaics
更新于2025-09-23 15:21:01
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Higha??Performance Nonfullerene Organic Solar Cells with Unusual Inverted Structure
摘要： A new fused-ring electron acceptor FOIC1 was designed and synthesized. FOIC1 exhibits intense absorption in the range of 600-1000 nm, HOMO/LUMO energy levels of –5.39/–3.99 eV, and electron mobility of 1.8 × 10–3 cm2 V–1 s–1. Organic solar cells based on sequentially processed heterojunction (SHJ) with unusual inverted structure were fabricated. Through sequentially spin-coating polymer donor PTB7-Th as the bottom layer and acceptor FOIC1 as the top layer, a better vertical phase distribution is formed in this SHJ compared with that in traditional bulk heterojunction (BHJ). In the upper-half part, a more balanced donor/acceptor distribution is beneficial for exciton dissociation. At the bottom interface, more FOIC1 accumulation is beneficial for exciton generation and charge transport. Overall, the SHJ cells exhibit power conversion efficiency as high as 12.0%, higher than that of the BHJ counterpart (11.0%).
关键词： sequential processing,inverted structure,nonfullerene,fused-ring electron acceptor,organic solar cell
更新于2025-09-23 15:21:01
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Improving the Electron Mobility of ITIC by End-Group Modulation: The Role of Fluorination and π-Extension
摘要： Nonfullerene organic solar cells (OSCs) using ITIC derivatives as electron acceptors have achieved power conversion efficiencies up to 14%, yet optimal active-layer thicknesses are still limited to (cid:1)100 nm, ascribed mainly to the (cid:3)4 cm2/Vs) of these acceptors. Because of the large steric hindrance of the bulky side chains on the fused-ring core, ITIC favors a local π–π stacking between the electron-withdrawing end groups (IC), which provides the main electron transport channel across the bulk volume. Here, the influence of different fluoro-substituted and π-extended (i.e., benzene-fused) positions in the phenyl moiety of IC on the electron transport properties is systematically investigated by multiscale theoretical simulations. It is found that the electron mobility can be remarkablely improved by proper fluorination and π-extension, especially by π-extension, due to the lower reorganization energy and stronger end-group π-π interaction. Moreover, a judicious combination of π-extension and fluorination can lead to a nearly six-fold increase of the electron mobility with respect to ITIC. This work shows that the electron mobility of A-D-A nonfullerene acceptors can be effectively improved by end-group engineering, paving the way toward higher-performance organic solar cells.
关键词： electron mobility,molecular packing,nonfullerene acceptor,end-group engineering
更新于2025-09-23 15:21:01
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Synthesis and Characterization of Wide-Bandgap Conjugated Polymers Consisting of Same Electron Donor and Different Electron-Deficient Units and Their Application for Nonfullerene Polymer Solar Cells
摘要： Substantial development has been made in nonfullerene small molecule acceptors (NFSMAs) that has resulted in a significant increase in the power conversion efficiency (PCE) of nonfullerene-based polymer solar cells (PSCs). In order to achieve better compatibility with narrow-bandgap nonfullerene small molecule acceptors, it is important to design the conjugated polymers with a wide bandgap that has suitable molecular orbital energy levels. Here two donor–acceptor (D–A)-conjugated copolymers are designed and synthesized with the same thienyl-substituted benzodithiophene and different acceptors, i.e., poly{(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)-alt-(1,3-bis(2-octyldodecyl)-1,3-dihydro-2H-dithieno[3′,2′:3,4;2″,3″:5,6]benzo[1,2-d]imidazol-2-one-5,8-diyl)} (DTBIA, P1) and poly{(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)-alt-(2-(5-(3-octyltridecyl)thiophen-2-yl)dithieno[3′,2′:3,4;2″,3″:5,6]benzo[1,2-d]thiazole-5,8-diyl)} (TDTBTA, P2) (and their optical and electrochemical properties are investigated). Both P1 and P2 exhibit similar deeper highest occupied molecular orbital energy level and different lowest unoccupied molecular orbital energy level. Both the copolymers have complementary absorption with a well-known nonfullerene acceptor ITIC-F. When blended with a narrow-bandgap acceptor ITIC-F, the PSCs based on P1 show a power conversion efficiency of 11.18% with a large open-circuit voltage of 0.96 V, a Jsc of 16.89 mA cm?2, and a fill factor (FF) of 0.69, which is larger than that for P2 counterpart (PCE = 9.32%, Jsc = 15.88 mA cm?2, Voc = 0.91 V, and FF = 0.645). Moreover, the energy losses for the PSCs based on P1 and P2 are 0.54 and 0.59 eV, respectively. Compared to P2, the P1-based PSCs show high values of incident photon to current conversion efficiency (IPCE) in the shorter-wavelength region (absorption of donor copolymer), more balanced hole and electron mobilities, and favorable phase separation with compact π–π stacking distance.
关键词： solvent vapor annealing,polymer solar cells,nonfullerene acceptors,wide-bandgap polymers
更新于2025-09-23 15:19:57
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Narrowbanda??Absorptiona??Type Organic Photodetectors for the Fara??Red Range Based on Fullerenea??Free Bulk Heterojunctions
摘要： Spectrally-selective photodetection via organic semiconductors manifesting narrowband absorption (NBA photodetection) is highly attractive for emerging applications that require ultrathin, lightweight, and low-cost solutions. While successful over mainstream color bands, NBA photodetectors have struggled so far to meet the functional and/or performance demands at longer wavelengths, importantly in the far-red (700–750 nm), a range relevant to diverse applications in analytical biology, medical diagnostics, remote sensing, etc. In consideration of the potential of a nonfullerene-acceptor route to address this challenge, the narrowband photodetection capabilities of SBDTIC, a recently-developed benzodithiophene-based acceptor with narrowband absorption in the far-red, are explored. Two bulk-heterojunction NBA configurations are considered, in which SBDTIC is combined with a donor either absorbing also in the far-red, or transparent through the visible. It is found that the latter configuration provides superior narrowband functionality, with peak detectivity of 1.42 × 1013 Jones and spectral width of 141 nm—the highest detectivity to date for NBA far-red-selective photodetectors, and the smallest spectral width of all solution-processed implementations. In self-powered operation, such photodetectors additionally present a quasilinear response over a photocurrent range of least four orders of magnitude, and respond in the microsecond range, further evidencing the suitability of this approach to address the wealth of target applications.
关键词： far-red,nonfullerene acceptors,narrowband-absorption photodetectors,organic photodetectors,narrowband photodetectors
更新于2025-09-23 15:19:57
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Thermally Durable Nonfullerene Acceptor with Nonplanar Conjugated Backbone for Higha??Performance Organic Solar Cells
摘要： A nonfullerene acceptor (NFA) with acceptor–donor–acceptor (A–D–A) architecture, i-IEICO-2F, based on 4,9-dihydro-s-indaceno[1,2-b:5,6-b′]dithiophene as an electron-donating core and 2-(6-fluoro-2,3-dihydro-3-oxo-1H-inden-1-ylidene)-propanedinitrile as electron-withdrawing end groups, is designed and synthesized. i-IEICO-2F has a twist structure in the main conjugated chain, which causes blueshifted absorption and leads to harmonious absorption with a high bandgap donor. The bandgap of i-IEICO-2F compliments the bandgap of suitable wide bandgap donor polymers such as J52, leading to complete light absorption throughout the visible spectrum. Devices based on i-IEICO-2F exhibit optimized photovoltaic performance including an open-circuit voltage of 0.93 V, a short-circuit current density of 16.61 mA cm?2, and a fill factor of 73%, and result in a power conversion efficiency (PCE) of 11.28%. The i-IEICO-2F-based devices reach PCEs of >11% without using any additives or post-treatments. Devices are found to be thermally stable and maintain 44% of their initial PCE after 184.5 h of continuous thermal annealing (TA) treatment at 150 °C. Based on UV, atomic force microscopy (AFM), and grazing incidence wide angle X-ray scattering (GIWAXS) results, i-IEICO-2F devices show almost identical morphology and molecular orientation throughout the TA treatment and excellent stability compared to other IEICO derivatives.
关键词： twist structure,solar cells,nonfullerene acceptors,synthesis,fluorine
更新于2025-09-23 15:19:57
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A 3D nonfullerene electron acceptor with a 9,9a?2-bicarbazole backbone for high-efficiency organic solar cells
摘要： One-dimensional ladder-type nonfullerene electron acceptors (NFAs) with large fused ring cores have been widely used in highly efficient organic solar cells (OSCs). Recent studies have demonstrated that small molecule acceptors with three-dimensional (3D) structures may exhibit low energy loss, and hence can lead to improved OSC performance. In this study, a new 3D NFA (99CZ-8F) with a 9,9'-bicarbazole backbone was designed, synthesized, and characterized, where two linear A-D-A architectures were linked by a single N-N bond. 99CZ-8F showed strong absorption in the range of 500-800 nm in the solid state, which is complementary to the absorption of the donor material PM6. After regulating the morphology of the active layer via binary solvent mixture, the optimized device exhibited a maximum power conversion efficiency (PCE) of 6.6 – 0.1 %, which is among the best reported values for 3D nonfullerene electron acceptor based OSCs.
关键词： Organic solar cells,end-capped groups,3D molecular structure,bicarbazole,nonfullerene electron acceptor
更新于2025-09-23 15:19:57
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Higha??Performance Pseudoplanar Heterojunction Ternary Organic Solar Cells with Nonfullerene Alloyed Acceptor
摘要： The vast majority of ternary organic solar cells are obtained by simply fabricating bulk heterojunction (BHJ) active layers. Due to the inappropriate distribution of donors and acceptors in the vertical direction, a new method by fabricating pseudoplanar heterojunction (PPHJ) ternary organic solar cells is proposed to better modulate the morphology of active layer. The pseudoplanar heterojunction ternary organic solar cells (P-ternary) are fabricated by a sequential solution treatment technique, in which the donor and acceptor mixture blends are sequentially spin-coated. As a consequence, a higher power conversion efficiency (PCE) of 14.2% is achieved with a Voc of 0.79 V, Jsc of 25.6 mA cm?2, and fill factor (FF) of 69.8% compared with the ternary BHJ system of 13.8%. At the same time, the alloyed acceptor is likely formed between two the acceptors through a series of in-depth explorations. This work suggests that nonfullerene alloyed acceptor may have great potential to realize effective P-ternary organic solar cells.
关键词： ternary organic solar cells,sequential spin-coating,pseudoplanar heterojunctions,nonfullerene alloyed acceptors
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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High Performance Organic Solar Cells Fabricated Using Recycled Transparent Conductive Substrates
摘要： The power conversion e?ciency (PCE) of organic solar cells (OSCs) has been gradually increasing over the past years, but these emerging photovoltaic devices still su?er from relatively short lifetimes. To promote circular economy and reduce costly electronic materials wastes, we explore the possibility of recycling durable zinc oxide coated indium tin oxide (ITO/ZnO) from nonfullerene OSCs through sequential ultrasonication in a series of solvents followed by thermal annealing. With the adequate cleaning sequence, the recycled ITO/ZnO substrates produce PCEs of 8.65%, a value comparable to the PCEs obtained with freshly prepared substrates (8.73%). Our results also indicate that isopropanol gradually removes the zinc oxide layer and should thus be avoided when attempting multiple successive recycling of the same substrate. ITO/ZnO substrates recycled 10 times with and without isopropanol yield PCEs of 5.14% and 7.93%, respectively. By optimizing the recycling procedure, we introduce a simple strategy to considerably increase the lifecycle of transparent electrode substrates employed in organic electronic devices and decrease the amount of wastes from the electronic industry.
关键词： Recycling,Zinc oxide,PBDB-T,Organic electronics,Nonfullerene acceptors
更新于2025-09-23 15:19:57