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Over 15% Efficiency Polymer Solar Cells Enabled by Conformation Tuning of Newly Designed Asymmetric Smalla??Molecule Acceptors
摘要： The prosperous period of polymer solar cells (PSCs) has witnessed great progress in molecule design methods to promote power conversion efficiency (PCE). Designing asymmetric structures has been proved effective in tuning energy level and morphology, which has drawn strong attention from the PSC community. Two hepta-ring and octa-ring asymmetric small molecular acceptors (SMAs) (IDTP-4F and IDTTP-4F) with S-shape and C-shape confirmations are developed to study the relationship between conformation shapes and PSC efficiencies. The similarity of absorption and energy levels between two SMAs makes the conformation a single variable. Additionally, three wide-bandgap polymer donors (PM6, S1, and PM7) are chosen to prove the universality of the relationship between conformation and photovoltaic performance. Consequently, the champion PCE afforded by PM7: IDTP-4F is as high as 15.2% while that of PM7: IDTTP-4F is 13.8%. Moreover, the S-shape IDTP-4F performs obviously better than their IDTTP-4F counterparts in PSCs regardless of the polymer donors, which confirms that S-shape conformation performs better than the C-shape one. This work provides an insight into how conformations of asymmetric SMAs affect PCEs, specific functions of utilizing different polymer donors to finely tune the active-layer morphology and another possibility to reach an excellent PCE over 15%.
关键词： small-molecule acceptors,power conversion efficiencies,polymer solar cells
更新于2025-09-23 15:19:57
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Efficient Modulation of End Groups for the Asymmetric Small Molecule Acceptors Enabling Organic Solar Cells with over 15% Efficiency
摘要： Non-fullerene organic solar cells (OSCs) have attracted tremendous interest and made an impressive breakthrough, largely due to advances in high-performance small molecule acceptors (SMAs). The relationship between short-circuit current density (JSC) and open-circuit voltage (VOC) is usually shown as one falls and another rises. Controlling the trade-off between JSC and VOC to harvest high power conversion efficiencies (PCEs) still remains as a challenge. Herein, dithieno[3,2-b:2?,3?-d]pyrrole (DTP) based asymmetric SMAs with different chlorinated dicyanoindanone-based end groups, named TPIC, TPIC-2Cl and TPIC-4Cl, are designed and synthesized. These asymmetric acceptors exhibit remarkable red-shifted absorption profile, while energy levels are simultaneously down-shifted when the numbers of chlorine atoms alter from 0, 1 to 2, due to the gradually improved electronegativity. As a result, PM7: TPIC-4Cl based OSCs achieved a champion PCE of 15.31%, which is the highest PCEs for non-fullerene binary OSCs based on asymmetric SMAs. The superiority of PM7: TPIC-4Cl system consists of the balanced charge transport, favorable phase separation, efficient exciton dissociation and extraction, coupled with remarkable π–π stacking and crystallinity of the SMAs. Our results highlight the important strategy of asymmetric molecular design to optimize the trade-off between VOC and JSC, reaching a high PCE.
关键词： asymmetric molecular design,small molecule acceptors,chlorinated dicyanoindanone-based end groups,Non-fullerene organic solar cells,power conversion efficiencies
更新于2025-09-19 17:13:59
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Effects of Short‐Axis Alkoxy Substituents on Molecular Self‐Assembly and Photovoltaic Performance of Indacenodithiophene‐Based Acceptors
摘要： The effects of central alkoxy side chain length of a series of narrow bandgap small molecule acceptors (SMAs) on their physicochemical properties and on the photovoltaic performance of the SMA-based polymer solar cells (PSCs) are systematically investigated. It is found that the ordered aggregation of these SMAs in films is enhanced gradually with the increase of alkoxy chain length. The single-crystal structures of these SMAs further reveal that small changes in the side chain length can have a dramatic impact on molecular self-assembly. The short-circuit current density and power conversion efficiency values of the corresponding PSCs increase with the increase of the side chain length of the SMAs. The π–π coherence length of the SMAs in the active layers is increased with the increase of the side chain length, which could be the reason for the increase of the Jsc in the PSCs. The results indicate that small changes in side chain length can have a dramatic impact on the molecular self-assembly, morphology, and photovoltaic performance of the PSCs. The structure–performance relationship established in this study can provide important instructions for the side chain engineering and for the design of efficient SMAs materials.
关键词： polymer solar cells,side chain engineering,morphology,small molecule acceptors,molecular self-assembly
更新于2025-09-19 17:13:59
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Asymmetrical side-chain engineering of small-molecule acceptors enable high-performance nonfullerene organic solar cells
摘要： Three new small molecules based on the benzo[1,2-b:4,5-b’]dithiophene (BDT) fused central core with different side-chains, namely DPBDT-4Cl, POBDT-4Cl and COBDT-4Cl, are designed and synthesized to investigate the side-chain effect on the properties of nonfullerene acceptors. DPBDT-4Cl has symmetrical phenylalkyl side-chains on the central BDT unit. In order to narrow the bandgap and reduce the steric hindrance, the phenylalkyl chains are systematically replaced with the flexible electron-donating alkoxy side-chain (POBDT-4Cl) and alkyl side-chain (COBDT-4Cl). As a result, POBDT-4Cl and COBDT-4Cl are characterized with asymmetry-featured side-chains. From DPBDT-4Cl to POBDT-4Cl to COBDT-4Cl, their light absorption abilities, molecular packing behaviors and crystallinity are gradually enhanced. The devices based on these three acceptors all show power conversion efficiencies (PCEs) over 11% with energy loss below 0.55 eV. Compared to DPBDT-4Cl, POBDT-4Cl and COBDT-4Cl obviously exhibit enhanced device performance with improved short-circuit current densities (Jsc) and fill factors (FFs), which mainly ascribe to their reduced charge recombination and enhanced charge transport. In addition, the COBDT-4Cl achieved a high efficiency of 13.5% with a Jsc of 21.8 mA cm-2 and an FF of 0.71. This result is among the best performance obtained from asymmetry-featured small molecules.
关键词： side-chains,benzo[1,2-b:4,5-b’]dithiophene,small-molecule acceptors,asymmetrical
更新于2025-09-19 17:13:59
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Significantly improving the performance of polymer solar cells by the isomeric ending-group based small molecular acceptors: Insight into the isomerization
摘要： Compared to benzene-fused end-capping groups (EGs), thiophene-fused EGs have some unique characteristics due to the non-centrosymmetric structure of the thiophene ring, which make them easy to form different types of isomers. Here, we develop three isomeric brominated thiophene-fused EGs, which are linked to the IDTT core to acquire three novel isomeric small-molecule acceptors (SMAs) named ITC-2Br, ITC-2Br1, and ITC-2Br2. From ITC-2Br to ITC-2Br1, the change of the bromine substituent group on the thiophene ring has only a minor impact on the physicochemical properties and photovoltaic performance. However, from ITC-2Br to ITC-2Br2, the change in the fused sites on the thiophene leads to dramatically modified absorption, energy levels, and photovoltaic performance. Theoretical simulations provide an in-depth understanding of the absorption and electrochemical differences among the three acceptors. Thanks to the favorable properties, the ITC-2Br2-based polymer solar cells (PSCs) yield a significantly higher power conversion efficiency (PCE) (13.1%) than the devices based on ITC-2Br (10.9%) and ITC-2Br1 (11.9%). From the ITC-2Br-, ITC-2Br1- to the ITC-2Br2-based devices, the JSC and FF exhibit a monotonic increase similar to the trend of PCE, which demonstrates the success of the isomerization strategy, highlighting its future prospects for the development of high-performance SMAs.
关键词： polymer solar cells,power conversion efficiency,isomerization,small-molecule acceptors,end-capping groups
更新于2025-09-16 10:30:52
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Achieving Efficient and Stable Morphology in Organic Solar Cells via Fine-tuning the Side-chains of Small Molecule Acceptors
摘要： Both the efficiency and stability of low cost organic solar cells are central components to meeting the requirements of commercialization for organic photovoltaics (OPV). Furthermore, the relationship between chemical structure of active material and morphology and its effects on efficiency and stability is still largely undetermined. Additionally, both the kinetic and thermodynamic morphology states of active layer can have a large impact on efficiency and stability, even when the chemical structures of materials applied in the active layer are especially same or similar. Here, using two series of acceptor-donor-acceptor (A-D-A) type small molecule acceptors (SMAs) with the similar backbone structure, we demonstrate the relevance of fine-tuned chemical structures with their solution and solid-state properties, further leading to significantly different behavior in terms of both device efficiency and stability. This is also partially due to the different morphology states caused by such fine chemical structure tuning. Our results indicate that a delicate balance of molecular aggregation and ordered stacking morphology is not only required to achieve but also could lead to both high efficiency and stability. Thus, among the two series of molecules, UF-EH-2F with both optimal length and steric hindrance of side-chains achieves the preponderant morphology in its corresponding device, where its morphology “Efficient State” and “Stable State” are almost overlapped and thus lead to both the highest efficiency (PCE = 13.56%) and best stability. Our results indicate that it is highly possible to achieve the morphology state required for both high efficiency and stability simultaneously by fine-tuning the chemical structure of active materials for organic solar cells.
关键词： small molecule acceptors,efficiency,side-chains,morphology,organic solar cells,stability
更新于2025-09-16 10:30:52
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Nonhalogenated-Solvent-Processed Efficient Polymer Solar Cells Enabled by Medium-Band-Gap A?π–D?π–A Small-Molecule Acceptors Based on a 6,12-Dihydro-diindolo[1,2- <i>b</i> :10,20- <i>e</i> ]pyrazine Unit
摘要： In this contribution, a series of A?π?D?π?A small molecules (SMs), IPY-T-IC, IPY-T-ICCl, and IPY-T-ICF, containing the central donor unit (D) of 6,12-dihydro-diindolo[1,2-b:10,20-e]pyrazine (IPY), the π-conjugated bridge of thiophene, and the end-accepting group (A) of 3-(dicyanomethylidene)indol-1-one, 5,6-dichloro-3-(dicyanomethylidene)indol-1-one, or 5,6-difluoro-3-(dicyanomethylene)indol-1-one, were developed, characterized, and employed as the acceptor materials for polymer solar cells (PSCs). Influences of the different end-accepting groups on thermal properties, spectral absorption, energy levels, photovoltaic performance, and film morphology of these small-molecule acceptors (SMAs) were investigated in detail. These SMAs exhibit an excellent thermal stability and strong crystallization. The absorption spectra of these SMs mainly locate the wavelength between 400 and 700 nm, associated with the optical band gaps in the range of 1.75?1.90 eV. Compared with nonhalogenated IPY-T-IC, the halogenated SMAs IPY-T-ICCl and IPY-T-ICF present better absorption abilities, wider absorption region, and downshifted highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) levels. With regard to the complementary spectral absorption and matched HOMO/LUMO levels, PTB7-Th as a low-band gap polymer was chosen to be an electron donor to pair with these SMAs for fabricating bulk-heterojuntion PSCs. Under optimized conditions, among these SMAs, the PTB7-Th:IPY-T-IC-based PSC processed from a halogenated solvent system (chlorobenzene + 1-chloronaphthalene) delivers the best power conversion efficiency (PCE) of 7.32%, mainly because of more complementary spectral absorption, upper-lying LUMO level, higher and balanced carrier mobility, more efficiently suppressed trap-assisted recombination, better charge collection property, and blend morphology. Encouragingly, an improved PCE of up to 7.68% is achieved when the IPY-T-IC-based solar cell was processed from a nonhalogenated solvent system (o-xylene + 2-methylnaphthalene). In view of the large band gap of these IPY-based SMAs, the PCE of over 7.5% is notable and attractive for the related community. Our study argues that the IPY moiety is a potential electron-donating building moiety to develop medium-band-gap high-performance A?π?D?π?A SMAs for nonhalogenated-solvent-processed photovoltaic devices.
关键词： A?π?D?π?A,polymer solar cells,small-molecule acceptors,6,12-dihydro-diindolo[1,2-b:10,20-e]pyrazine,photovoltaic performance
更新于2025-09-12 10:27:22
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Solution-Processable All-Small-Molecule for High-Performance Nonfullerene Organic Solar Cells with High Crystallinity Acceptor
摘要： In this work, two small molecule acceptors (IDIC and IDIC-4F) with different crystallinity and energy level have been successfully applied in nonfullerene-based all-small molecule organic solar cells (NFASM-OSCs). The donor of DFDT(DPP)2 was chosen because of complementary absorption with IDIC and IDIC-4F. As acceptor, IDIC-4F exhibited a higher PCE than IDIC due to better crystallinity. This work not only shows us how to balance the relationship between Voc and Jsc, but also suggests us how to get a good phase separation morphology. Moreover, Increased crystallinity helps to inhibit bimolecular recombination and increase charge mobility. By optimizing device preparation conditions, the best PCE of 9.43% for DFDT(DPP)2 : IDIC-4F as active layer was achieved with excitable Jsc (16.83 mA cm-2) and FF (0.65). The FF and Jsc of resultant device show a significant increased which is among the top efficiencies based on DPP as terminal acceptor groups of NFSM-OSCs reported in document up to now.
关键词： crystallinity,small molecule acceptors,phase separation morphology,nonfullerene organic solar cells,charge mobility
更新于2025-09-11 14:15:04
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Chalcogen‐Fused Perylene Diimides‐Based Non‐Fullerene Acceptors for High Performance Organic Solar Cells: Insight into the Effect of O, S and Se
摘要： Three perylene diimide tetramers annulated by oxygen (O), sulfur (S) and selenium (Se), named as SF-4PDI-O, SF-4PDI-S and SF-4PDI-Se, are designed, synthesized and paired with polymeric donor PDBT-T1 to construct OSCs. The heteroatoms’ effect on photoelectric properties, chemical geometry, charge transport, active-layer morphology, and photovoltaic performance are investigated in detail. These PDI acceptors exhibit similar absorption profile; while HOMOs and LUMOs are simultaneously upshifted when heteroatoms are altered from O, S to Se due to the gradually weakening electronegativity. Alongside PDBT-T1, SF-4PDI-O achieved the outstanding PCE of 8.904% with a high FF of 0.706, outcompeting its S-annulated and Se-annulated counterparts. The superiority of PDBT-T1: SF-4PDI-O system lies in stronger crystallinity, more balanced hole and electron mobilities, weaker bimolecular recombination, coupled with more efficient charge transfer and collection. These results shed light on the invention of high-performance PDI acceptors by oxygen-decorated methodology.
关键词： chalcogen,nonfullerene,organic solar cells,perylene diimides,small molecule acceptors
更新于2025-09-11 14:15:04