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Synthesis and Characterization of Wide-Bandgap Conjugated Polymers Consisting of Same Electron Donor and Different Electron-Deficient Units and Their Application for Nonfullerene Polymer Solar Cells
摘要： Substantial development has been made in nonfullerene small molecule acceptors (NFSMAs) that has resulted in a significant increase in the power conversion efficiency (PCE) of nonfullerene-based polymer solar cells (PSCs). In order to achieve better compatibility with narrow-bandgap nonfullerene small molecule acceptors, it is important to design the conjugated polymers with a wide bandgap that has suitable molecular orbital energy levels. Here two donor–acceptor (D–A)-conjugated copolymers are designed and synthesized with the same thienyl-substituted benzodithiophene and different acceptors, i.e., poly{(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)-alt-(1,3-bis(2-octyldodecyl)-1,3-dihydro-2H-dithieno[3′,2′:3,4;2″,3″:5,6]benzo[1,2-d]imidazol-2-one-5,8-diyl)} (DTBIA, P1) and poly{(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)-alt-(2-(5-(3-octyltridecyl)thiophen-2-yl)dithieno[3′,2′:3,4;2″,3″:5,6]benzo[1,2-d]thiazole-5,8-diyl)} (TDTBTA, P2) (and their optical and electrochemical properties are investigated). Both P1 and P2 exhibit similar deeper highest occupied molecular orbital energy level and different lowest unoccupied molecular orbital energy level. Both the copolymers have complementary absorption with a well-known nonfullerene acceptor ITIC-F. When blended with a narrow-bandgap acceptor ITIC-F, the PSCs based on P1 show a power conversion efficiency of 11.18% with a large open-circuit voltage of 0.96 V, a Jsc of 16.89 mA cm?2, and a fill factor (FF) of 0.69, which is larger than that for P2 counterpart (PCE = 9.32%, Jsc = 15.88 mA cm?2, Voc = 0.91 V, and FF = 0.645). Moreover, the energy losses for the PSCs based on P1 and P2 are 0.54 and 0.59 eV, respectively. Compared to P2, the P1-based PSCs show high values of incident photon to current conversion efficiency (IPCE) in the shorter-wavelength region (absorption of donor copolymer), more balanced hole and electron mobilities, and favorable phase separation with compact π–π stacking distance.
关键词： solvent vapor annealing,polymer solar cells,nonfullerene acceptors,wide-bandgap polymers
更新于2025-09-23 15:19:57
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Nonfullerene organic photovoltaic cells exhibiting 13.76% efficiency by employing upside‐down solvent vapor annealing
摘要： Organic photovoltaic cells (OPVs) are fabricated with a polymer donor PM7 and a nonfullerene acceptor IT‐4Cl; the morphology of active layers is optimized by employing upside‐down solvent vapor annealing (UD‐SVA) method with different annealing solvents. The OPVs with CS2 as annealing solvent exhibit optimized power conversion efficiency (PCE) of 13.76%, with simultaneously increased short‐circuit current density (JSC) of 20.53 mA cm?2 and fill factor (FF) of 77.05%. More than 15% PCE improvement can be achieved by employing CS2 UD‐SVA treatment, which should be attributed to slightly enhanced photon harvesting, efficient exciton separation, charge transport, and collection, resulting from the well‐developed morphology of active layer. Moreover, the PM7:IT‐4Cl–based OPVs with CS2 as annealing solvent still can maintain PCE more than 13% in a wide treatment time range from 20 to 90 seconds. This work demonstrated that UD‐SVA has great potential in improving the performance of nonfullerene OPVs.
关键词： phase separation,organic photovoltaic cells,solvent vapor annealing,nonfullerene
更新于2025-09-19 17:13:59
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Interfacial Energetic Level Mapping and Nano-Ordering of Small Molecule/Fullerene Organic Solar Cells by Scanning Tunneling Microscopy and Spectroscopy
摘要： Using scanning tunneling microscopy (STM) and spectroscopy (STS) at the liquid/solid interface, morphology evolution process and energetic level alignment of very thin solid films (thickness: <700 pm), of the low molecular weight molecule DRCN5T and DRCN5T:[70]PCBM blend are analyzed after applying thermal annealing at different temperatures. These films exhibit a worm-like pattern without thermal annealing (amorphous shape); however, after applying thermal annealing at 120 °C, the small molecule film domains crystallize verified by X-ray diffraction: structural geometry becomes a well-defined organized array. By using STS, the energy band diagrams of the semiconductor bulk heterojunction (blended film) at the donor-acceptor interface are determined; morphology and energy characteristics can be correlated with the organic solar cells (OSC) performance. When combining thermal treatment and solvent vapor annealing processes as described in previous literature by using other techniques, OSC devices based on DRCN5T show a very acceptable power conversion efficiency of 9.0%.
关键词： solvent vapor annealing,DRCN5T,scanning tunneling spectroscopy,organic solar cells,scanning tunneling microscopy,thermal annealing
更新于2025-09-16 10:30:52
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[IEEE 2019 26th International Workshop on Active-Matrix Flatpanel Displays and Devices (AM-FPD) - Kyoto, Japan (2019.7.2-2019.7.5)] 2019 26th International Workshop on Active-Matrix Flatpanel Displays and Devices (AM-FPD) - PEDOT:PSS Transparent Electrode for ITO-Free Polymer:Fullerene Bulk-Heterojunction Organic Solar Cells
摘要： Conducting poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films have high potential as flexible transparent conductive electrodes in various devices. In this study, two simple robust methanol-based treatment methods, namely, dipping process (DP) and solvent vapor annealing (SVA), were used to improve the electrical conductivity of PEDOT:PSS films in order to make them suitable as electrodes in organic solar cells (OSCs). Then, the characteristics of the methanol-treated PEDOT:PSS films were investigated. After the methanol treatments, the sheet resistance of the PEDOT:PSS films (ca. 100 ?/Sq) were improved by more than 200 times, and the work function (~5.0 eV) was nearly unchanged in both methods. Two completely different possible origins of the improved conductivity of the methanol-treated PEDOT:PSS films were addressed for DP and SVA approaches. Both methods were suitable for preparing methanol-treated PEDOT:PSS films that can be used as anodes for polymer–fullerene-based OSCs. The photovoltaic performance of the modified PEDOT:PSS-based devices was comparable to that of indium tin oxide (ITO)-based devices, thus demonstrating their practicality. The methanol-treated PEDOT:PSS films show great potential as flexible transparent conductive electrodes for ITO-free and metal-free devices.
关键词： dipping process,solvent vapor annealing,organic solar cells,methanol treatment,transparent electrode,PEDOT:PSS
更新于2025-09-11 14:15:04
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Optimized mixed phases to achieve improved performance of organic solar cells
摘要： In the three-phase (pure donor, pure acceptor, and mixed phases) morphologies of organic solar cells, the mixed phases produce an energy cascade that promotes the generation of free carriers. However, how to optimize the content of the mixed phases is a challenging problem. The authors proposed to control different content of mixed phases in DRTB-T and IDIC blends by additive and solvent vapor annealing (SVA). The authors ?rst formed the largest extent amount of mixed phases by the additive cinene (2%) to inhibit the crystallization of DRTB-T and IDIC. And then, different amounts of mixed phases were achieved by further SVA for different times (from 0 to 50 s) to increase the content of pure DRTB-T and IDIC phases. The energetic offsets (ΔE) of pure and mixed phases gradually decrease from 0.529 to 0.477 eV for different content of mixed phases. When ΔE was 0.498 eV, the highest photocurrent density (Jsc) was obtained. The power conversion ef?ciency was increased from 3.23% (without any treatment) to 8.54%. Therefore, the authors demonstrated that the optimized content of the mixed phases is critical to device performance.
关键词： solvent vapor annealing,additive,organic solar cells,power conversion efficiency,DRTB-T,energy cascade,cinene,IDIC,mixed phases
更新于2025-09-11 14:15:04