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Achieving Fast Charge Separation and Low Nonradiative Recombination Loss by Rational Fluorination for High‐Efficiency Polymer Solar Cells
摘要： Four low-cost copolymer donors of poly(thiophene-quinoxaline) (PTQ) derivatives are demonstrated with different fluorine substitution forms to investigate the effect of fluorination forms on charge separation and voltage loss (Vloss) of the polymer solar cells (PSCs) with the PTQ derivatives as donor and a A–DA’D–A-structured molecule Y6 as acceptor. The four PTQ derivatives are PTQ7 without fluorination, PTQ8 with bifluorine substituents on its thiophene D-unit, PTQ9, and PTQ10 with monofluorine and bifluorine substituents on their quinoxaline A-unit respectively. The PTQ8- based PSC demonstrates a low power conversion efficiency (PCE) of 0.90% due to the mismatch in the highest occupied molecular orbital (HOMO) energy levels alignment between the donor and acceptor. In contrast, the devices based on PTQ9 and PTQ10 show enhanced charge-separation behavior and gradually reduced Vloss, due to the gradually reduced nonradiative recombination loss in comparison with the PTQ7-based device. As a result, the PTQ10-based PSC demonstrates an impressive PCE of 16.21% with high open-circuit voltage and large short-circuit current density simultaneously, and its Vloss is reduced to 0.549 V. The results indicate that rational fluorination of the polymer donors is a feasible method to achieve fast charge separation and low Vloss simultaneously in the PSCs.
关键词： voltage loss,nonradiative recombination,low-cost copolymer donors,fluorination,charge separation
更新于2025-09-12 10:27:22
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Backbone Fluorination of Polythiophenes Improves Device Performance of Non-Fullerene Polymer Solar Cells
摘要： Polythiophenes (PTs) are promising donor materials for the industrialization of polymer solar cells (PSCs) due to the merits of easy synthesis, low cost, and large-scale producibility. The rapid progress of non-fullerene acceptors requires the development of new PTs for use in non-fullerene PSCs. In this work, we present a set of PTs with different degree of backbone fluorination (P6T-F00, P6T-F50, P6T-F75, and P6T-F100) to investigate the effect of fluorination on the photovoltaic properties of PTs in non-fullerene PSCs. Upon increasing fluorine content, the PTs tend to have higher crystallinity, higher absorption coefficients, and enhanced relative dielectric constants. When blended with a non-fullerene acceptor EH-IDTBR, the blend films show increased photoluminescence quenching efficiency, reduced charge recombination loss, and extended charge carrier lifetime along with increasing fluorine content of PTs. These positive factors collectively result in dramatically improved power conversion efficiency from 4.3% for P6T-F00:EH-IDTBR to 7.3% for P6T-F100:EH-IDTBR, which is superior to the champion binary non-fullerene PSCs based on P3HT. Our results demonstrate that PTs are promising donor materials for non-fullerene PSCs via backbone fluorination.
关键词： polythiophenes,polymer solar cells,backbone fluorination,dielectric constant,non-fullerene acceptors
更新于2025-09-11 14:15:04
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Propeller-like acceptors with difluoride perylene diimides for organic solar cells
摘要： Perylene diimide (PDI) is one of most intensively studied non-fullerene small molecule acceptors (SMAs). By fluorination on the conjugated backbone, a new PDI with difluoride substitution on adjacent bay positions of PDI is prepared. Then, four propeller-like SMAs are obtained by linking four PDIs with an aromatic core, wherein the molecular geometry is modulated by ring fusion of the aromatic core. Further study reveals that fluorination is helpful to enhance the absorption intensity, and thus promote the current density in organic solar cells. In addition, the ring-fused strategy is able to suppress the distortion and rotation of relevant molecules. Therefore, these four acceptors exhibit significantly diversity of photovoltaic performance, wherein the acceptor FPDIF4-DTC consisting of a fused core and fluoro-substituted PDIs shows a best efficiency of 5.1%. This result implies that fluorination on PDI conjugated backbone is a successful way to construct promising SMAs.
关键词： Perylene Diimide,Fluorination,Non-fullerene acceptor,Organic solar cells
更新于2025-09-11 14:15:04
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Hydrogenation and Fluorination of 2D Boron Phosphide and Boron Arsenide: A Density Functional Theory Investigation
摘要： First-principles density functional theory calculations are performed to study the stability and electronic properties of hydrogenated and fluorinated two-dimensional sp3 boron phosphide (BP) and boron arsenide (BAs). As expected, the phonon dispersion spectrum and phonon density of states of hydrogenated and fluorinated BX (X = P, As) systems are found to be different, which can be attributed to the different masses of hydrogen and fluorine. Hydrogenated BX systems bear larger and indirect band gaps and are found to be different from fluorinated BX systems. These derivatives can be utilized in hydrogen storage applications and ultrafast electronic devices. Finally, we investigated the stability and electronic properties of stacked bilayers of functionalized BP. Interestingly, we found that these systems display strong interlayer interactions, which impart strong stability. In contrast with the electronic properties determined for the fluorinated/hydrogenated monolayers, we found that the electronic properties of these bilayers can finely be tuned to a narrow gap semiconductor, metallic or nearly semimetallic one by selecting a suitable arrangement of layers. Moreover, the nearly linear dispersion of the conduction band edge and the heavy-, light-hole bands are the interesting characteristics. Furthermore, the exceptional values of effective masses assure the fast electronic transport, making this material very attractive to construct electronic devices.
关键词： boron phosphide,boron arsenide,hydrogenation,fluorination,density functional theory,electronic properties,stability
更新于2025-09-10 09:29:36
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[IEEE 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) - Greifswald, Germany (2018.9.23-2018.9.28)] 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) - Measurement of Surface Potential Distribution of Fluorinated Polyimide Film
摘要： Metal-Dielectric-Metal structure is widely applied in many pulsed power systems, such as electro-vacuum devices, high power microwave equipment and particle accelerators. This kind of composite insulation is suffered with high gradient electric field, which may result in phenomena of surface flashover across the dielectric. Corresponding surface charges and trap characteristics are important parameters, determining final flashover. This paper is focused on surface charges distribution (SCD) and trap measurement of fluorinated polyimide film, to investigate influences of fluorination on surface potential distribution. Additionally, the treatment methods of fluorination including fluorinated gas proportion and applied time have significant influences on SCD. The improvement of SCD can lead to flashover threshold improvement. These results are effective to illuminate theoretical mechanism of fluorination suppression and optimize the treatment process.
关键词： trap characteristics,polyimide film,surface potential distribution,surface fluorination
更新于2025-09-09 09:28:46