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Enabling low voltage losses and high photocurrent in fullerene-free organic photovoltaics
摘要： Despite significant development recently, improving the power conversion efficiency of organic photovoltaics (OPVs) is still an ongoing challenge to overcome. One of the prerequisites to achieving this goal is to enable efficient charge separation and small voltage losses at the same time. In this work, a facile synthetic strategy is reported, where optoelectronic properties are delicately tuned by the introduction of electron-deficient-core-based fused structure into non-fullerene acceptors. Both devices exhibited a low voltage loss of 0.57 V and high short-circuit current density of 22.0 mA cm?2, resulting in high power conversion efficiencies of over 13.4%. These unconventional electron-deficient-core-based non-fullerene acceptors with near-infrared absorption lead to low non-radiative recombination losses in the resulting organic photovoltaics, contributing to a certified high power conversion efficiency of 12.6%.
关键词： non-fullerene acceptors,power conversion efficiency,voltage losses,charge separation,organic photovoltaics
更新于2025-11-14 15:18:02
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Progress of the key materials for organic solar cells
摘要： Organic solar cells have attracted academic and industrial interests due to the advantages like lightweight, flexibility and roll-to-roll fabrication. Nowadays, 18% power conversion efficiency has been achieved in the state-of-the-art organic solar cells. The recent rapid progress in organic solar cells relies on the continuously emerging new materials and device fabrication technologies, and the deep understanding on film morphology, molecular packing and device physics. Donor and acceptor materials are the key materials for organic solar cells since they determine the device performance. The past 25 years have witnessed an odyssey in developing high-performance donors and acceptors. In this review, we focus on those star materials and milestone work, and introduce the molecular structure evolution of key materials. These key materials include homopolymer donors, D-A copolymer donors, A-D-A small molecular donors, fullerene acceptors and nonfullerene acceptors. At last, we outlook the challenges and very important directions in key materials development.
关键词： D-A copolymer donors,nonfullerene acceptors,key materials,organic solar cells,fullerene acceptors
更新于2025-09-23 15:21:01
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Small bandgap non-fullerene acceptor enables efficient PTB7-Th solar cell with near 0 eV HOMO offset
摘要： Three small bandgap non-fullerene (SBG NFAs) acceptors, BDTI, BDTI-2F and BDTI-4F, based on a carbon-oxygen bridged central core and thieno[3,4-b]thiophene linker, end-capped with varied electron-withdrawing terminal groups, were designed and synthesized. The acceptors exhibit strong absorption from 600 nm to 1000 nm. The optimal device incorporating designed NFA and PTB7-Th polymer donor achieves a power conversion efficiency of 9.11% with near 0 eV HOMO offset. The work presents a case study of efficient non-fullerene solar cells with small HOMO offsets, which is achieved by blending PTB7-Th with fine-tuned SBG acceptor.
关键词： Organic solar cells,Driving force,HOMO offset,Non-fullerene acceptors,Small bandgap
更新于2025-09-23 15:21:01
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Ternary Organic Solar Cells Based on two Non-fullerene Acceptors with Complimentary Absorption and Balanced Crystallinity
摘要： The ternary blend structure has been demonstrated as an effective approach to increase the power conversion efficiency of organic solar cells. An effective approach to enhance the power conversion efficiency of ternary solar cells is based on two non-fullerene acceptors with complimentary absorption range and balanced crystalinity. In this work, by introducing a high crystallinity small-molecule acceptor, named C8IDTT-4Cl with appropriate alkyl side chains into a low crystalline blend of conjugated polymer donor PBDT-TPD and fused-ring electron acceptor ITIC-4F. A ternary device based on the blend PBDT-TPD:ITIC-4F:C8IDTT-4Cl exhibits a best power conversion efficiency of 9.51% with a simultaneous improvement of the short-circuit current density to 18.76 mA cm-2 and the fill factor up to 67.53%. The absorption onset for C8IDTT-4Cl is located at 900 nm, so that the well complementary light absorption is beneficial to the photocurrent. In addition, the existence of high crystallinity C8IDTT-4Cl in the ternary device is found helpful to modulate crystallinity, improve heterojunction morphologies and stacking structure, therefore to realize higher charge mobility and better performance.
关键词： Non-fullerene Acceptors,Ternary Organic Solar Cells,Power Conversion Efficiency,Complimentary Absorption,Balanced Crystallinity
更新于2025-09-23 15:21:01
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Non-fullerene small molecule acceptors with three-dimensional thiophene/selenophene-annulated perylene diimides for efficient organic solar cells
摘要： Three-dimensional non-fullerene acceptors with a spiro core linked with S/Se fused perylene diimides possess appropriate energy levels, twisted molecular configuration and high carrier mobility, leading to a power conversion efficiency of 6.95% for the organic solar cells.
关键词： perylene diimides,organic solar cells,carrier mobility,non-fullerene acceptors,spiro core
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 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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Towards photovoltaic windows: scalable fabrication of semitransparent modules based on non-fullerene acceptors <i>via</i> laser-patterning
摘要： Semitransparent organic photovoltaics (OPV) possess unique properties that make them highly appealing for their integration into semitransparent architectonic elements such as windows or glazings. In order to provide sufficient transparency, non-opaque electrodes and thin photoactive layers are typically used, thus limiting the light-harvesting capacity. This can be partially overcome by using materials that absorb light mostly in the infrared region. On the other hand, the use of scalable techniques for the fabrication of semitransparent devices is often disregarded. In this work, we combine the blue, low-bandgap polymer PBTZT-stat-BDTT-8 with the near-infrared absorbing non-fullerene acceptor 4TICO, adapting the module fabrication to low-cost manufacturing processes that are compatible with large-scale production. Fully solution-processed semitransparent solar cells over 4.7% performance are prepared from non-chlorinated formulations, in air and using scalable techniques such as blade coating. Our prototypes of semitransparent laser-patterned OPV modules exceed 30% of transparency (measured as human perception transmittance, HPT) and yield efficiencies in the range of 4%, geometrical fill factors surpassing 90% and an active area above 1 cm2. We verify the quality of cell-to-cell interconnection and optimise the geometry of the modules with the help of local optoelectronic imaging techniques. This work highlights the relevance of non-fullerene acceptors with strong absorption in the near-infrared, as they can meet industrial and technical requirements for the upscaling and integration of high-performance semitransparent OPV modules with low production costs.
关键词： scalable fabrication,laser-patterning,non-fullerene acceptors,photovoltaic windows,semitransparent organic photovoltaics
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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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