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Efficient defect passivation of perovskite solar cells via stitching organic bidentate molecule
摘要： The defects present in the solution-processed perovskite light absorbing materials are responsible for deteriorating the performance and stability of perovskite solar cells. Therefore, suppressing of the defect formation and passivating the pre-existing defects in perovskite materials is of paramount importance in pushing the efficiency of perovskite solar cell (PSC) toward the theoretical limit and ensuring the long-term stability of PSC. In this work, we report an efficient defect passivation route using a bidentate small organic molecule, pyrazine, which is capable of making either a monodentate or a bridging bidentate bonding with under-coordinated Pb2+ ions mainly present in the surface and grain-boundary of perovskite films. The various analyses for defect density and charge carrier lifetime of perovskite light absorbing layer demonstrated that the pyrazine effectively passivated defects existing on the surface and grain boundary of the perovskite films without affecting the morphology and crystallinity via a simple post-treatment procedure. As a result, the best untreated device obtained a power conversion efficiency of 19.14 %, while the efficiency of 20.58 % was achieved with pyrazine treated.
关键词： bidentate molecule,defect passivation,charge carrier lifetime,perovskite solar cells,pyrazine
更新于2025-09-19 17:13:59
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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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Effects of Pyrazine Derivatives and Substituted Positions on the Photoelectric Properties and Electromemory Performance of D–A–D Series Compounds
摘要： Pyrazine derivatives quinoxaline and pyridopyrazine were selected as the acceptors, and benzocarbazole was used as the donor to synthesize four different D–A–D compounds. The results showed that 2,3-bis(decyloxy)pyridine[3,4-b]pyrazine (DPP) exhibited stronger electron-withdrawing ability than that of 2,3-bis(decyloxy)quinoxaline (DPx), because DPP possesses one more nitrogen (N) atom, resulting in a red-shift of the intramolecular charge transfer (ICT) absorption bands and ?uorescent emission spectra for compounds with DPP as the acceptor compared with those that use DPx as the acceptor. The band-gap energy (Eg) of the four D–A–D compounds were 2.82 eV, 2.70 eV, 2.48 eV, and 2.62 eV, respectively, for BPC-2DPx, BPC-3DPx, BPC-2DPP, and BPC-3DPP. The solvatochromic effect was insigni?cant when the four compounds were in the ground state, which became signi?cant in an excited state. With increasing solvent polarity, a 30–43 nm red shift was observed in the emissive spectra of the compounds. The thermal decomposition temperatures of the four compounds between 436 and 453 ?C had very high thermal stability. Resistor-type memory devices based on BPC-2DPx and BPC-2DPP were fabricated in a simple sandwich con?guration, Al/BPC-2DPx/ITO or Al/BPC-2DPP/ITO. The two devices showed a binary non-volatile ?ash memory, with lower threshold voltages and better repeatability.
关键词： quinoxaline,photoelectric properties,donor-acceptor-donor,pyrazine,electromemory,benzocarbazole
更新于2025-09-10 09:29:36
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Synthesis and Characterization of Four Random copolymers Containing Fluorene as Electron Donors and Benzotriazole, Benzothiadiazole, Pyrido[3,4-b]pyrazine as Electron Acceptors
摘要： Four random copolymers containing fluorene as electron donors and benzotriazole, benzothiadiazole, pyrido[3,4-b]pyrazine as electron acceptors were successfully synthesized. Afterwards, a series of characterization, including cyclic voltammetry (CV), spectroelectrochemistry, kinetics, colorimetry and thermal gravimetric analysis were carried out to fully investigate the properties of the copolymers we got. Their band gaps are 1.87 eV, 1.91 eV, 1.97 eV and 1.98 eV, respectively. From neutral state to oxidized state, PFPP changes from thistle to transparent gray, PBTFPP changes from tan to transparent gray, PBTFBD changes from sienna to lightslategray, and PBDFBD changes from rosybrown to lightgrey. The coloration efficiencies are 269.91cm2·C-1 for PFPP, 177.45cm2·C-1 for PBTFPP, 241.92cm2·C-1 for PBTFBD, and 174.67cm2·C-1 for PBDFBD in near infrared region. Except for PFPP, all the other three copolymers are stable and could be good candidates in electrochromic application.
关键词： benzothiadiazole,fluorene,benzotriazole,conducting polymers,pyrido[3,4-b]pyrazine
更新于2025-09-10 09:29:36
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Tetrakis(oxadiazolylphenyl)pyrazines: New St. Andrew's Cross- Shaped Liquid Crystals
摘要： π-Conjugated molecules with the shape of St. Andrews cross have been synthesized via fourfold Huisgen reaction. Four 2,5-diaryl-1,3,4-oxadiazol arms are attached to a central pyrazine nucleus. These fluorescent stars, when decorated with a rim of eight alkoxy side chains are discotic liquid crystals. Depending on the substitution pattern, the width of the liquid phase varies within a broad range of 25 °C to 250 °C. In their liquid crystalline phase, the molecules assemble in a typical hexagonal columnar supramolecular arrangement.
关键词： solvatochromism,liquid crystals,WAXS,POM,pyrazine
更新于2025-09-10 09:29:36