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The Balance between Energy Transfer and Exciton Separation in Ternary Organic Solar Cells with Two Conjugated Polymer Donor
摘要： Ternary strategy as a straightforward way for organic solar cells (OSCs) to improve the device performance attracts many interests in the field. The ternary strategy usually focuses on processing the third light-absorbing material owning a complementary absorption to the binary system. However, studying the third component with similar absorption spectra to the binary counterpart is equally essential to understand the in-depth mechanism of the performance improvement from the third component. In this work, we filled up this blank and derived a type of ternary device consisting of two conjugated polymer donor materials of PTB7-Th and PffBT4T-2OD and non-fullerene acceptor material of IEICO-4F. The average PCE value of the optimized ternary device reached 12.1%, which is around 16% higher than its PTB7-Th:IEICO-4F binary counterpart. Even the third component of PffBT4T-2OD containing a similar absorption spectrum with PTB7-Th, it was found that the Jsc increase contributes to the primary performance enhancement. Further investigations indicate that the Jsc increase in the optimized ternary device mainly came from the improved light absorption ability, current extraction process, charge transport process, and suppressed non-radiative recombination. Moreover, there is a balance found between the exciton separation process and the energy transfer process when optimizing ternary blend ratios. The optimized ternary device is suspected to reach this balance point and thus exhibits the enhancement in device performance. Morphology investigation reveals that the addition of PffBT4T-2OD can tune the morphology and increase the crystallinity in the active layer. The optimized ternary blend shows a well-mixed donor and acceptor morphology with small domain size and slightly increased crystallization, which further explained its best device performance.
关键词： non-fullerene,energy transfer,exciton separation,organic solar cells,ternary,crystallization,conjugated polymer
更新于2025-09-23 15:21:01
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A wide-bandgap nonplanar small molecule acceptor having indenofluorene core for non-fullerene polymer solar cells
摘要： Recently, the nonplanar non-fullerene acceptors (NFAs) are attractive in active layers in highly efficient polymer solar cells (PSCs) because of their up-shifted energy levels, improved absorption as well as charge transportation performances. However, presently nonplanar NFAs always absorb the lights in the long-wavelength region and even to near-infrared (NIR) region, which limits their further utilization in low-bandgap polymer donor-based PSCs. To further probe the performances of nonplanar NFAs in low-bandgap polymer-based PSCs, a new twisted NFA (i-IF-4F) having indenofluorene derivatives as the electron-donating fused-ring core was synthesized. Due to the relatively weak electron-donating ability of the indenofluorene core, this newly designed NFA has wide optical bandgap (1.79 eV) with absorption spectrum ranged from 450 to 690 nm, suitable lowest unoccupied molecular orbital (LUMO, -3.71 eV) and highest occupied molecular orbital (HOMO, -5.55 eV) energy levels, which ensure its matching well with the typically low-bandgap polymer (PTB7-Th) to achieve complementary absorption and proper differences in energy levels. After thermal annealing treatment, the film morphologies, charge transfer properties and charge recombination performances of i-IF-4F:PTB7-Th-based device was improved to a certain degree, leading to an optimized power conversion efficiency (PCE) of 6.47%. The work in this manuscript demonstrates the applicability of wide-bandgap twisted acceptors in PSCs and the possible approach to further improve the performances of wide-bandgap nonplanar acceptors in PSCs.
关键词： Polymer solar cells,Indenofluorene,Main-chain twisted small molecules,Wide bandgap non-fullerene acceptors
更新于2025-09-23 15:21:01
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Sa?ˉCl intramolecular interaction: An efficient strategy to improve power conversion efficiency of organic solar cells
摘要： Noncovalent conformational locks (NCLs) including S···N, Se···O, and S···O etc. have been an effective strategy to improve the planarity and rigidity, and charge transport mobility of organic/polymeric semiconductors. Herein, by replacing methyl group (ITMIC) with chlorine (ITCIC) in the π-bridge, the planarity and rigidity of the π-conjugated skeleton was enhanced by introduction of S···Cl NCLs, thus the charge transport mobility was improved accordingly. As a result, PM6:ITCIC based organic solar cells showed impressive PCE of 11.34%, much higher than that based on PM6:ITMIC. This contribution demonstrated a novel kind NCLs (S···Cl) for improving the performance of organic solar cells.
关键词： noncovalent conformational locks,organic solar cells,non-fullerene acceptor,charge transport mobility
更新于2025-09-23 15:21:01
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Narrowing the Band Gap: The Key to High-Performance Organic Photovoltaics
摘要： Organic photovoltaics (OPVs) have attracted considerable attention in the last two decades to overcome the terawatt energy challenge and serious environmental problems. During their early development, only wide-band-gap organic semiconductors were synthesized and employed as the active layer, mainly utilizing photons in the UV?visible region and yielding power conversion e?ciencies (PCEs) lower than 5%. Afterward, considerable e?orts were made to narrow the polymer donor band gap in order to utilize the infrared photons, which led to the enhancement of the PCE from 5% to 12% in about a decade. Since 2017, the study of narrow-band-gap non-fullerene acceptors helped usher in a new era in OPV research and boosted the achievable the PCE to 17% in only 3 years. In essence, the history of OPV development in the last 15 years can be summarized as an attempt to narrow the band gap of organic semiconductors and better position the energy levels. There are multiple bene?ts of a narrower band gap: (1) considerable infrared photons can be utilized, and as a result, the short-circuit current density can increase signi?cantly; (2) the energy o?set of the lowest unoccupied molecular orbital energy levels or highest occupied molecular orbital energy levels between the donor and acceptor can be reduced, which will reduce the open-circuit voltage loss by minimizing the loss caused by the donor/acceptor charge transfer state; (3) because of the unique molecular orbitals of organic semiconductors, the red-shifted absorption will induce high transmittance in the visible region, which is ideal for the rear subcells in tandem-junction OPVs and transparent OPVs.
关键词： Organic photovoltaics,narrow-band-gap,non-fullerene acceptors,power conversion efficiencies,polymer donors
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Degradation Mechanism Identified for the Fullerene and Non-fullerene based Organic Solar Cells under Ambient Condition
摘要： Solution-processed organic solar cells (OSCs) have becoming a promising photovoltaic technology for a low-cost electricity generation. However, poor stability of OSCs is still a severe problem need to be understood and solved for future application. In this work, we conducted an air stability study for both fullerene and non-fullerene based OSCs. As a result, the degradation mechanism was found different for these two types of OSCs. The Urbach energy determined the EQE measurement indicates that the air-degradation in fullerene based OSCs is mainly ascribed to its increased energetic disorder. Differently, the photoluminescence (PL) measurement implied that the air-degradation in non-fullerene based OSCs mainly results from the degraded charge dissociation and energy transfer ability. Therefore, different stability improving strategy will be needed for fullerene and non-fullerene based OSCs in future.
关键词： non-fullerene,air stability,degradation mechanism,fullerene,organic solar cells
更新于2025-09-23 15:19:57
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Non-Fused Non-Fullerene Acceptors with an Aa??Da??A'a??Da??A Framework and a Benzothiadiazole Core for High-Performance Organic Solar Cells
摘要： Non-fullerene acceptors (NFAs) have contributed significantly to the progress of organic solar cells (OSCs). However, most NFAs featured a large fused-ring backbone, which usually require tedious multiple-step synthesis and are not applicable to commercial application. An alternative strategy is to develop non-fused NFAs, which possess synthetic simplicity and facile tunability in optoelectronic properties and solid-state microstructures. In this work, we report two non-fused NFAs, BTCIC and BTCIC-4Cl, based on an A?D?A'?D?A architecture, which possess the same electron-deficient benzothiadiazole central core but different electron-withdrawing terminal groups. The optical properties, energy levels, and molecular crystallinities were finely tuned by changing the terminal groups. Moreover, a decent power conversion efficiency of 9.3% and 10.5% has been achieved by BTCIC and BTCIC-4Cl, respectively, by blending them with an appropriate polymer donor. These results demonstrate the potential of A?D?A'?D?A type non-fused NFAs for high-performance OSCs. Further development of non-fused NFAs will be very fruitful by employing appropriate building blocks and via side chain optimizations.
关键词： A?D?A'?D?A framework,benzothiadiazole,organic solar cells,non-fused acceptors,non-fullerene acceptors
更新于2025-09-23 15:19:57
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Non-halogenated solvent-processed ternary-blend solar cells via alkyl-side-chain engineering of a non-fullerene acceptor and its application in large-area devices
摘要： A novel asymmetric non-fullerene acceptor (T2-OEHRH) with a simple chemical structure is designed and synthesized. Compared with the symmetric T2-ORH, T2-OEHRH effectively suppresses excessive self-aggregation/crystallization and substantially improves the solubility without sacrificing photoelectrical properties. As a result, T2-OEHRH-based ternary-blend OSCs processed from a non-halogenated solvent exhibit impressive PCEs of 12.10% and 9.32% in small- and large-area devices, respectively.
关键词： non-fullerene acceptor,large-area solar cells,ternary-blend solar cells,non-halogenated solvent,asymmetric alkyl side-chain
更新于2025-09-23 15:19:57
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Higha??Performance Ternary Organic Solar Cells with Morphologya??Modulated Hole Transfer and Improved Ultraviolet Photostability
摘要： Ternary bulk-heterojunction (BHJ) strategy synergistically combining the merits of fullerene and non-fullerene acceptors has been regarded as a promising approach to enhance the power conversion efficiencies (PCEs) of organic solar cells (OSCs). Herein, the fullerene derivative ICBA as the morphology regulator is incorporated into non-fullerene based PBDB-T-2F:BTP-4Cl (PM6:BTP-4Cl) system to fabricate the high-performance ternary OSCs. The amorphous ICBA prefers to homogeneously distribute in the BTP-4Cl phase to form the well-mixed acceptor domains due to their better miscibility, which distinctly reduces the exciton decay loss driven by the unfavorable phase separation and enhances BHJ morphology stability of ternary blends. The appropriate addition of ICBA induces the efficient long-range F?rster resonance energy transfer to BTP-4Cl and facilitates the ultrafast hole transfer process from BTP-4Cl to PM6, thereby contributing to charge carrier generation in the actual devices. Ultimately, the optimal ternary OSCs not only yield the average PCE higher than 16.5% but also show the superior ultraviolet photostability relative to binary control devices owing to the increased harvesting of ultraviolet photons, boosted charge transfer, more balanced charge transport and more stable nano-structural morphology. Our results provide the new insights to enable the simultaneously improved device performance and tolerance to UV light in highly efficient ternary OSCs.
关键词： hole transfer,non-fullerene,ultraviolet photostability,ternary organic solar cells
更新于2025-09-23 15:19:57
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Simultaneous improvement of three parameters using binary processing solvent approach in as-cast non-fullerene solar cells
摘要： As-cast polymer solar cells without any additive and pre- or post-treatment principally are of high compatibility with mass production technologies, whose efficiencies are typically promoted by new donor and acceptor materials. In this work, a binary solvent approach using chloroform (CF) of low boiling point as good solvent for both polymer donor PTQ10 and non-fullerene acceptor IT-4Cl and mesitylene (MES) of relatively high boiling point as a semi-orthogonal co-solvent due to weaker solubility to the acceptor is explored. Due to the selective orthogonality of MES to the IT-4Cl acceptor, an optimized morphology has been realized for the as-cast device based on the PTQ10:IT-4Cl blend, which leads to a simultaneous improvement in the open-circuit voltage, short-circuit current, and fill factor, finally achieving a high as-cast efficiency of over 13%. Furthermore, the as-cast devices fabricated with the binary solvent can exhibit good air stability and great accessibility in large area cells. Our findings provide an alternative guideline for the optimization of the as-cast polymer solar cells.
关键词： polymer solar cells,morphology optimization,non-fullerene acceptor,binary solvent,as-cast
更新于2025-09-23 15:19:57
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Efficient Organic Solar Cells Based on Non-Fullerene Acceptors with Two Planar Thiophene Fused Perylene Diimide Units
摘要： We designed and synthesized two non-fullerene acceptors (CDT-TFP and C8X-TFP), which comprise a central 4H-cyclopenta[2,1-b:3,4-b’]dithiophene (CDT) as the bridge and two thiophene-fused perylene diimide (TFP) units. The bulky side chains, such as the 4-hexylphenyl side chains, on the CDT bridge can effectively prevent the acceptor molecules from forming large aggregates and the π-π stacking of the terminal planar TFP units can form effective electron transport pathways when blending with the donor polymers. These non-fullerene acceptors are used to fabricate organic solar cells (OSCs) by blending with regioregular middle bandgap polymer reg-PThE. The as-cast devices based on reg-PThE:CDT-TFP show the best PCE of 8.36% with a Voc of 1.10 V, Jsc of 12.43 mA cm-2 and FF of 61.4%; whereas, the analogue PDI dimers (CDT-PDI) that comprising two PDI units bridged with a CDT unit, show only a 2.59% PCE with a Voc of 0.92 V, Jsc of 6.82 mA cm-2 and FF of 41.5%. Our results have demonstrated that non-fullerene acceptors comprising planar PDI units can achieve excellent photovoltaic performance and provide meaningful guidelines for the design of PDI based non-fullerene electron acceptors for efficient OSCs.
关键词： regioregular donor polymer,perylene diimide,organic solar cells,non-fullerene electron acceptors,planar
更新于2025-09-23 15:19:57