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Designing dithienonaphthalene based acceptor materials with promising photovoltaic parameters for organic solar cells
摘要： Scientists are focusing on non-fullerene based acceptors due to their efficient photovoltaic properties. Here, we have designed four novel dithienonaphthalene based acceptors with better photovoltaic properties through structural modification of a well-known experimentally synthesized reference compound R. The newly designed molecules have a dithienonaphthalene core attached with different 2-(5,6-difluoro-2-methylene-3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (H1), 2-(5,6-dicyano-2-methylene-3-oxo-2,3-dihydroinden-1-ylidene)-malononitrile (H2), 2-(5-methylene-6-oxo-5,6-dihydrocylopenta[c]thiophe-4-ylidene)-malononitrile (H3) and 2-(3-(dicyanomethylene)-2,3-dihydroinden-1-yliden)malononitrile (H4) acceptor moieties (end-capped). The photovoltaic parameters of the designed molecules are discussed in comparison with those of the reference R. All newly designed molecules show a reduced HOMO–LUMO energy gap (2.17 eV to 2.28 eV), compared to the reference R (2.31 eV). Charger transfer from donor to acceptor is confirmed by a frontier molecular orbital (FMO) diagram. All studied molecules show extensive absorption in the visible region and absorption maxima are red-shifted compared to R. All investigated molecules have lower excitation energies which reveal high charge transfer rates, as compared to R. To evaluate the open circuit voltage, the designed acceptor molecules are blended with a well-known donor PBDB-T. The molecule H3 has the highest Voc value (1.88 V). TDM has been performed to show the behaviour of electronic excitation processes and electron hole location between the donor and acceptor unit. The binding energies of all molecules are lower than that of R. The lowest is calculated for H3 (0.24 eV) which reflects the highest charge transfer. The reorganization energy value for both the electrons and holes of H2 is lower than R which is indicative of the highest charge transfer rate.
关键词： absorption maxima,binding energies,reorganization energy,photovoltaic properties,open circuit voltage,charge transfer,dithienonaphthalene,HOMO–LUMO energy gap,non-fullerene based acceptors
更新于2025-09-12 10:27:22
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Comparative study on the effects of alkylsilyl and alkylthio side chains on the performance of fullerene and non-fullerene polymer solar cells
摘要： Two novel high gap donor polymers – PBDTTSi-TzBI and PBDTTS-TzBI, based on imide fused benzotriazole (TzBI) with asymmetric side chains and alkylsilyl (Si) or alkylthio (S) substituted 4,8-di(thien-2-yl)benzo[1,2-b:4,5-b′]dithiophene (BDTT) – are successfully synthesized. The effect of the side chain variation on the photophysical, morphological and photovoltaic properties of blends of these polymers with fullerene and non-fullerene acceptors is investigated. The PBDTTSi-TzBI polymer shows a deeper highest occupied molecular orbital energy level, which results in higher open-circuit voltages. Nevertheless, the polymer solar cells fabricated using PBDTTS-TzBI in combination with PC71BM afford a higher power conversion efficiency of 7.3% (vs 4.0% for PBDTTSi-TzBI:PC71BM). By using the non-fullerene acceptor ITIC, the absorption of the blends extends to 850 nm and better device efficiencies are achieved, 6.9% and 9.6% for PBDTTSi-TzBI:ITIC and BDTTS-TzBI:ITIC, respectively. The better performance for PBDTTS-TzBI:ITIC is attributed to the strong and broad absorption and balanced charge transport, and is among the best so far for non-fullerene solar cells based on TzBI-containing polymer donors.
关键词： Alkylthio,Benzotriazole,Alkylsilyl,Polymer solar cells,Non-fullerene acceptors,Photovoltaic properties
更新于2025-09-11 14:15:04
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Quantum Dots Improve Photovoltaic Properties of Purple Membranes under Near-Infrared Excitation
摘要： Purple membrane (PMs), in which the photosensitive protein bacteriorhodopsin (bR) naturally occurs, have photovoltaic properties and are promising for optoelectronic applications. However, PMs cannot effectively absorb light in the NIR spectral region. Semiconductor quantum dots (QDs), which have high two-photon absorption cross-sections in the NIR region, can significantly improve the light sensitivity of PMs by means of F?rster resonance energy transfer (FRET) from QDs to bR inside PMs. The purpose of this study was to improve the photovoltaic properties of PMs by means of FRET from QDs to bR under NIR two-photon excitation. We made the QD-PM complexes and showed high FRET efficiency in them. Finally, we found that the current signal from the QD-PM material was higher than that in the case of PMs alone under NIR excitation. The obtained results clearly demonstrate improvement of the photovoltaic properties of PMs under NIR two-photon excitation due to the FRET from QDs to bR and show the prospect of designing new photosensitive bio-nanohybrid devices.
关键词： Near-Infrared Excitation,F?rster Resonance Energy Transfer,Purple Membranes,Photovoltaic Properties,Quantum Dots
更新于2025-09-11 14:15:04
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Spin coated multilayered CuO/ZnO films with high output power under irradiation
摘要： Thin films of pure CuO, pure ZnO and CuO/ZnO multilayers were synthesized using the spin coating technique. CuO and ZnO layers were spin coated for 30 s at speeds of 2000 and 1500 rpm, respectively. All the samples were subsequently annealed at 500 0C for one hour in air. Structural properties of films investigated using XRD patterns indicated the crystallization of single phase of CuO and ZnO. Optical band gaps of samples determined by UV-Visible spectrums were in the range of the band gaps of CuO and ZnO. The main objective of the preparation of multilayered CuO/ZnO was enhancing the output power by combining wide band gap and narrow band gap materials. CuO with higher photocurrent and ZnO with higher photovoltage were employed to achieve this task. Photocurrent, photovoltage and impedance were measured in order to investigate the electrical properties of these samples. A liquid junction photocell with electrolyte potassium iodide (KI) was employed to measure photovoltaic properties. A multilayer with ZnO as the top layer provides a higher output power of 3.6 μW/cm2 compared to the output power of a multilayer with CuO as the top layer (1.1 μW/cm2). This is the highest output power reported for a multilayer of CuO/ZnO without any dye coating in KI electrolyte. The highest output power of our multilayered samples is more than twice the previously reported highest output powers of pure CuO and pure ZnO thin film samples without dye coating. Chemical properties of samples were confirmed by FTIR. Crystallite sizes were in the range from 23 to 28 nm. Impedance curves of the samples were measured under dark and light conditions. Two semicircles could be observed at Nyquist plots of both multilayer samples.
关键词： photovoltaic properties,spin coating,XRD,Cupric Oxide,multilayers,Zinc Oxide
更新于2025-09-04 15:30:14