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Higha??Performance Nonfullerene Organic Solar Cells with Unusual Inverted Structure
摘要： A new fused-ring electron acceptor FOIC1 was designed and synthesized. FOIC1 exhibits intense absorption in the range of 600-1000 nm, HOMO/LUMO energy levels of –5.39/–3.99 eV, and electron mobility of 1.8 × 10–3 cm2 V–1 s–1. Organic solar cells based on sequentially processed heterojunction (SHJ) with unusual inverted structure were fabricated. Through sequentially spin-coating polymer donor PTB7-Th as the bottom layer and acceptor FOIC1 as the top layer, a better vertical phase distribution is formed in this SHJ compared with that in traditional bulk heterojunction (BHJ). In the upper-half part, a more balanced donor/acceptor distribution is beneficial for exciton dissociation. At the bottom interface, more FOIC1 accumulation is beneficial for exciton generation and charge transport. Overall, the SHJ cells exhibit power conversion efficiency as high as 12.0%, higher than that of the BHJ counterpart (11.0%).
关键词： sequential processing,inverted structure,nonfullerene,fused-ring electron acceptor,organic solar cell
更新于2025-09-23 15:21:01
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Achieving Optimal Bulk Heterojunction in All-Polymer Solar Cells by Sequential Processing with Nonorthogonal Solvents
摘要： Developing efficient all-polymer solar cells (all-PSCs) has always been a long-standing challenge due to the unfavorable morphology caused by conventional blend-casting (BC). Here we first employ the methodology of sequential processing (SP) with nonorthogonal solvents to fabricate facilely all-PSCs. A highly crystalline polymer donor PBDB-T is used to construct a well-organized underlying film, while a new polymer FPDI-BT1 is selected as the acceptor to be intercalated into the amorphous or semicrystalline regions of PBDB-T during the secondary deposition. By tuning the solvent composition for FPDI-BT1 processing, a bulk heterojunction-like configuration, rather than a traditional bilayer device, is obtained facilely without the need of further processing treatment. The extremely boosted power conversion efficiency of 7.15% from SP device is achieved, which is more than twice as efficient as the BC analogue (3.57%). The results demonstrate that SP is a promising strategy to fabricate high-performance all-PSCs with tunable configurations of active layers.
关键词： perylene diimide,non-fullerene acceptor,sequential processing,all-polymer solar cells,morphological control
更新于2025-09-19 17:13:59
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Designing Conjugated Polymers for Molecular Doping: The Roles of Crystallinity, Swelling, and Conductivity in Sequentially-Doped Selenophene-Based Copolymers
摘要： Although chemical doping is widely used to tune the optical and electrical properties of semiconducting polymers, it is not clear how the degree of doping and the electrical properties of the doped materials vary with the bandgap, valence band level, and crystallinity of the polymer. We address this question utilizing a series of statistical copolymers of poly(3-hexylthiophene) (P3HT) and poly(3-heptylselenophene) (P37S) with controlled gradients in bandgap, valence band position and variable crystallinity. We dope the copolymers in our series with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) using solution sequential processing (SqP). We then examine the structures of the films using grazing incidence wide-angle x-ray scattering (GIWAXS), differential scanning calorimetry (DSC) and ellipsometric porosimetry, and the electrical properties of the films via the AC Hall effect. We find that the ability of a particular copolymer to be doped is largely determined by the offset of the polymer’s valence band energy level relative to the LUMO of F4TCNQ. The ability of the carriers created by doping to be highly mobile and thus contribute to the electrical conductivity, however, is controlled by how well the polymer can incorporate the dopant into its crystalline structure, which is in turn influenced by how well it can be swelled by the solvent used for dopant incorporation. The interplay of these effects varies in a non-monotonic way across our thiophene:selenophene copolymer series. The position and shape of the polaron absorption spectrum correlate well with the polymer crystallinity and carrier mobility, but the polaron absorption amplitude does not reflect the number of mobile carriers, precluding the use of optical spectroscopy to accurately estimate the mobile carrier concentration. Overall, we find that the degree of crystallinity of the doped films is what best correlates with conductivity, suggesting that only carriers in crystalline regions of the film, where the dopant counterions and polarons are forced apart by molecular packing constraints, produce highly mobile carriers. With this understanding, we are able to achieve conductivities in this class of materials exceeding 20 S/cm.
关键词： semiconducting polymers,conductivity,ellipsometric porosimetry,GIWAXS,solution sequential processing,valence band level,F4TCNQ,poly(3-heptylselenophene),AC Hall effect,poly(3-hexylthiophene),DSC,bandgap,chemical doping,crystallinity
更新于2025-09-04 15:30:14