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Modulation of donor alkyl terminal chains with shifting branching point leads to optimized morphology and efficient all-small-molecule organic solar cells
摘要： Terminal group modification is one of the most influential factors for small molecular donors compared with their polymer counterparts, resulting in an opportunity to optimize the morphology of all-small-molecule organic solar cells (ASM-OSCs). In this manuscript, we report three novel small molecular donors with branching points at the 1-, 2-, and 3-positions in alkyl terminal chains, called BSCl-C1, BSCl-C2 and BSCl-C3, respectively. Using IDIC-4Cl as acceptor, the subtle branching position shift achieves a dramatic disparity in photovoltaic parameters, as indicated by the short circuit current (Jsc) changing from 4.90 mA cm?2 to 20.1 mA cm?2 to 14.2 mA cm?2 and the fill factor varying from 33.9% to 71.3% to 67.0% for BSCl-C1, BSCl-C2, and BSCl-C3, respectively. The best device performance of 12.4% is obtained by the BSCl-C2:IDIC-4Cl system, which not only ranks among the top values reported to date, but also exhibits low energy loss in systems that use IDIC as acceptors. The notable device performance based on BSCl-C2 is attributed to the optimized phase morphology caused by the strong molecular crystallinity and suitable intermolecular interaction with IDIC-4Cl. These results demonstrate that suitably tuning the branching position of terminal groups could promote the high performance of ASM-OSCs.
关键词： branching point,phase morphology,crystallinity,intermolecular interaction,all-small-molecule
更新于2025-09-23 15:21:01
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Tuning the hybridization of local exciton and chargea??transfer states in highly efficient organic photovoltaic cells
摘要： Decreasing the energy loss is one of the most feasible ways to improve the efficiencies of organic photovoltaic (OPV) cells. Recent studies have suggested that non-radiative energy loss (ΔEnr) is the dominant factor that hinders further improvements in state-of-the-art OPV cells. However, there is no rational molecular design strategy for OPV materials with suppressed ΔEnr. In this work, taking molecular surface electrostatic potential (ESP) as a quantitative parameter, we establish a general relationship between chemical structure and intermolecular interactions. The results reveal that increasing the ESP difference between donor and acceptor will enhance the intermolecular interaction. In the OPV cells, the enhanced intermolecular interaction will increase the charge transfer (CT) state ratio in its hybridization with local exciton to facilitate the charge generation but simultaneously result in a larger ΔEnr. These results suggest that finely tuning the ESP of OPV materials is a feasible method to further improve the efficiencies of OPV cells.
关键词： hybridization,charge transfer state,intermolecular interaction,organic photovoltaic cells,non-radiative energy loss
更新于2025-09-23 15:19:57
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15.3% efficiency all-small-molecule organic solar cells enabled by symmetric phenyl substitution; ???????ˉ1?§°??§è?ˉ??o???é￥°?????°??????é??è??15.3%?????¨?°? ????-??????o?¤aé?3è????μ?±?;
摘要： Synergistic optimization of donor-acceptor blend morphologyis a hurdle in the path of realizing efficient non-fullerene small-molecule organic solar cells (NFSM-OSCs) due to the anisotropic conjugated backbones of both donor and acceptor. Therefore, developing a facile molecular design strategy to effectively regulate the crystalline properties of photoactive materials, and thus, enable the optimization of blend morphology is of vital importance. In this study, a new donor molecule B1, comprising phenyl-substituted benzo-dithiophene (BDT) central unit, exhibits strong interaction with the non-fullerene acceptor BO-4Cl in comparison with its corresponding thiophene-substituted BDT-based material, BTR. As a result, the B1 is affected and induced from an edge-on to a face-on orientation by the acceptor, while the BTR and the acceptor behave individually for the similar molecular orientation in pristine and blend films according to grazing incidence wide angle X-ray scattering results. It means the donor-acceptor blend morphology is synergistically optimized in the B1 system, and the B1:BO-4Cl-based devices achieve an outstanding power conversion efficiency (PCE) of 15.3%, further certified to be 15.1% by the National Institute of Me-trology, China. Our results demonstrate a simple and effective strategy to improve the crystalline properties of the donor molecule as well as synergistically optimize the morphology of the all-small-molecule system, leading to the high-performance NFSM-OSCs.
关键词： all-small-molecule,intermolecular interaction,crystallinity,organic solar cells,non-fullerene
更新于2025-09-23 15:19:57
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Spirobifluorene-based oligopyridine derivatives as electron-transporting materials for green phosphorescent organic light-emitting diodes
摘要： The electron-transporting materials (ETMs), 2,7-bis(3,5-di(pyridin-3-yl)phenyl)-9,9'-spirobi[fluorene] (3-4PySF) and 2,7-bis(3,5-di(pyridin-4-yl)phenyl)-9,9'-spirobi[fluorene] (4-4PySF) were designed and synthesized by combining spirobifluorene moiety with di(pyridine-3-yl)phenyl and di(pyridine-4-yl)phenyl, respectively. The spirobifluorene moiety improves materials’ rigid twisted structure to ensure the morphological stability of amorphous film, and pyridine acts as electron acceptor to enhance electron-transporting ability of materials. The dependence of electron-transporting property on the position of substituted pyridine rings was studied. The melting point (Tm) of 4-4PySF is estimated to be 41 ℃ higher than that of 3-4PySF. And the higher current density in the electron only devices exhibited by 4-4PySF revealed the effect of nitrogen atom position on the charge-transporting properties. Green PhOLEDs based on bis(2-phenylpyridine)iridium(III)(2,2,6,6-tetramethylheptane-3,5-diketonate) (Ir(ppy)2tmd) as the emitter and 3-4PySF, 4-4PySF and 1,3,5-tris(N-phenylbenzimidazol-2-yl-benzene (TPBi) as ETMs were fabricated. Compared to the device based on the conventional ETM TPBi, the devices based on new ETMs exhibited a higher maximum external quantum efficiency (EQE) of 20.5% and a lower turn-on voltage (Von) of 2.6 V.
关键词： electron-transporting material,intermolecular interaction,oligopyridine,organic light-emitting diode,spirobifluorene
更新于2025-09-19 17:13:59
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Tuning the hybridization of local exciton and chargea??transfer states in highly efficient organic photovoltaic cells
摘要： Decreasing the energy loss is one of the most feasible ways to improve the efficiencies of organic photovoltaic (OPV) cells. Recent studies have suggested that non-radiative energy loss ( ) is the dominant factor that hinders further improvements in state-of-the-art OPV cells. However, there is no rational molecular design strategy for OPV materials with suppressed . In this work, taking molecular surface electrostatic potential (ESP) as a quantitative parameter, we establish a general relationship between chemical structure and intermolecular interactions. The results reveal that increasing the ESP difference between donor and acceptor will enhance the intermolecular interaction. In the OPV cells, the enhanced intermolecular interaction will increase the charge transfer (CT) state ratio in its hybridization with local exciton to facilitate the charge generation but simultaneously result in a larger . These results suggest that finely tuning the ESP of OPV materials is a feasible method to further improve the efficiencies of OPV cells.
关键词： hybridization,charge transfer state,intermolecular interaction,organic photovoltaic cells,non-radiative energy loss
更新于2025-09-19 17:13:59
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Cation-controlled luminescence behavior of anionic cyclometalated platinum(II) complexes
摘要： The characteristic luminescence properties of anionic cyclometalated Pt(II) complexes are discussed from the viewpoint of the counter cations. To date, various cyclometalated Pt(II) complexes have been developed as promising luminescent materials because cyclometalating ligands provide stable and strong ligand fields. In addition to the molecular design of cyclometalated Pt(II) complexes, control of the intermolecular interactions is particularly important for Pt(II) complexes with square-planar geometry. In this context, we focus on the effects of counter cations on anionic cyclometalated Pt(II) complexes by classifying such complexes into three categories, i.e., (i) systems with bulky organic cations, which enable the formation of isolated Pt(II) complexes, (ii) systems with non-innocent cations, which interact with anionic Pt(II) complexes through dative bonds or charge transfer, and (iii) systems including adaptable cations, which support the assembly of the Pt(II) complexes by cancelling out the electrostatic repulsion between Pt(II) complex anions that form stacking structures with Pt···Pt interactions. For this category, the formation and properties of ionic liquids using asymmetric cations is discussed.
关键词： Luminescence,Chromic behavior,Cation-controlled anionic complex,Intermolecular interaction,Cyclometalated platinum(II) complex
更新于2025-09-16 10:30:52
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Probing Self-associated Intermolecular H-bonding using low-frequency SERS coupled with mid-IR SERS and DFT Study: A case study of 2-MBA adsorbed on ZnO nanoparticles
摘要： In the present study, low-frequency SERS is reported for the first time to investigate the intermolecular interaction. The low-frequency SERS in THz region (>50 cm-1) and the mid-IR region is used to probe the H-bonding interaction in 2-mercaptobenzoic acid (2-MBA) molecules adsorbed on the surface of ZnO nanoparticles. The self-association due to H-bonding leads to dimer formation of 2-MBA through carboxylic acid groups. The characteristics Raman bands of 2-MBA dimer; H-bonded O-H stretching and out-of-plane O-H bending modes are observed. Subsequently, this dimer formation causes the evolution of two new low-frequency modes at 90 cm-1 (shear dimer in-plane bending) and 110 cm-1 (shear dimer stretching) of intermolecular H-bonding and blue-shift of the torsional mode of (–COOH) + (–SH). In the THz region (50-200 cm-1), vibrational modes are blue-shifted while in the mid-IR region, symmetric out-of-plane O-H bending is red-shifted. The present work shows that SERS can be used to study intermolecular H-bonding of molecules at very low concentration.
关键词： Intermolecular interaction,Low-frequency,SERS,H-bonding
更新于2025-09-11 14:15:04