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Developing Wide Bandgap Polymers with Single Benzodithiophene-Based Unit for Efficient Polymer Solar Cells
摘要： In this work, a series of solely benzodithiophene-based wide bandgap polymer donors, namely PBDTT, PBDTS, PBDTF and PBDTCl, were developed for efficient polymer solar cells (PSCs) by just varying the heteroatoms into the conjugated side chains. The effects of sulfuration, fluorination and chlorination were also investigated systematically on the overall properties of these BDT-based polymers. The HOMO levels could be lowered gradually by introducing sulfur, fluorine and chlorine atoms into the side chains, which contributed to the stepwise increased Voc (from 0.78 V to 0.84 V) in the related PSCs using Y6 as the electron acceptor. On the other hand, above side chain engineering strategy could promote the polymer chain interactions and fine-tune the phase separation of active blends, leading to the enhanced absorption, ordered molecular packing and crystallinity. Among them, the chlorinated PBDTCl exhibited not only high level absorption and crystallinity, but also the most balanced hole/electron charge transport and the most optimized morphology, giving rise to the best PCE of 13.46% with a Voc of 0.84 V, a Jsc of 23.16 mA cm-2 and an FF of 69.2 %. The chlorination strategy afforded PBDTCl synthetic simplicity but high efficiency, showing its promising photovoltaic applications for realizing low-cost practical PSCs in near future.
关键词： synthetic simplicity,benzodithiophene,sole donor unit,wide bandgap polymer donors,polymer solar cells
更新于2025-09-23 15:21:01
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Narrowing the Band Gap: The Key to High-Performance Organic Photovoltaics
摘要： Organic photovoltaics (OPVs) have attracted considerable attention in the last two decades to overcome the terawatt energy challenge and serious environmental problems. During their early development, only wide-band-gap organic semiconductors were synthesized and employed as the active layer, mainly utilizing photons in the UV?visible region and yielding power conversion e?ciencies (PCEs) lower than 5%. Afterward, considerable e?orts were made to narrow the polymer donor band gap in order to utilize the infrared photons, which led to the enhancement of the PCE from 5% to 12% in about a decade. Since 2017, the study of narrow-band-gap non-fullerene acceptors helped usher in a new era in OPV research and boosted the achievable the PCE to 17% in only 3 years. In essence, the history of OPV development in the last 15 years can be summarized as an attempt to narrow the band gap of organic semiconductors and better position the energy levels. There are multiple bene?ts of a narrower band gap: (1) considerable infrared photons can be utilized, and as a result, the short-circuit current density can increase signi?cantly; (2) the energy o?set of the lowest unoccupied molecular orbital energy levels or highest occupied molecular orbital energy levels between the donor and acceptor can be reduced, which will reduce the open-circuit voltage loss by minimizing the loss caused by the donor/acceptor charge transfer state; (3) because of the unique molecular orbitals of organic semiconductors, the red-shifted absorption will induce high transmittance in the visible region, which is ideal for the rear subcells in tandem-junction OPVs and transparent OPVs.
关键词： Organic photovoltaics,narrow-band-gap,non-fullerene acceptors,power conversion efficiencies,polymer donors
更新于2025-09-23 15:21:01
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Non-halogenated-solvent-processed highly efficient organic solar cells with a record open circuit voltage enabled by noncovalently locked novel polymer donors
摘要： The relatively low open circuit voltage (Voc) of organic solar cells (OSCs) with narrow and ultra-narrow bandgap fused-ring electron acceptors limits further improvement of the OSCs. Simply down-shifting the highest occupied molecular orbital (HOMO) levels of the donors always results in the trade-off between the Voc and short circuit current (Jsc). In this work, we reported three novel noncovalently locked polymer donors based on different side-chain-modified benzodithiophene (BDT) units alternately copolymerized with an electron-deficient 3,30-dicarboxylate-substituted difluorotetrathiophene building block for efficient OSCs. Due to the existence of the electron-affinity moiety, deep HOMO levels are obtained for these copolymer donors, enabling the highest recorded Voc of 0.99 V when blended with the IT-4F acceptor. Meanwhile, intramolecular noncovalent interactions in these copolymers favor a preferential face-on orientation. Efficient charge transport and exciton dissociation under a low driving force are observed in these novel polymer donors. Consequently, the device processed from a non-halogenated solvent shows a high efficiency of 12.5% with simultaneously high Voc and Jsc, which is one of the highest performances of non-halogenated-solvent-processed OSCs to date. These results demonstrate that the synergistic effect of the energy band structure and molecular geometry can provide an effective molecular design strategy for high performance OSCs.
关键词： noncovalently locked polymer donors,organic solar cells,open circuit voltage,non-halogenated-solvent-processed,high efficiency
更新于2025-09-16 10:30:52
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Benzodithiophenedione-based polymers: recent advances in organic photovoltaics
摘要： Over the past 20 years, significant progress has been made in organic photovoltaics (OPVs) due to its advantages of being cost-effective, being lightweight, and having flexible manufacturability. The optical-active layer of OPVs consists of a p-type polymer as the donor and an n-type small molecule as the acceptor. An efficient design strategy of a polymer donor is based on an alternating electron-donating unit (D) and an electron-accepting unit (A). Among numerous electron-accepting units, an emerging annelated thiophene of benzodithiophenedione (BDD) has exhibited a distinguished photovoltaic performance because of its planar molecular structure, low-lying highest occupied molecular orbit (HOMO) level and good self-assembly property. In this review article, we summarize the most recent developments in BDD-based photovoltaic materials. Special attention is paid to the chemical structure-property relationships, such as the absorption, bandgap, energy levels, mobilities, and photovoltaic performances. The empirical regularities and perspectives on the future development of BDD-based photovoltaic materials are included.
关键词： chemical structure-property relationships,benzodithiophenedione,photovoltaic performance,polymer donors,organic photovoltaics
更新于2025-09-16 10:30:52
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Understanding of Imine Substitution in Wide Bandgap Polymer Donor–Induced Efficiency Enhancement in All-Polymer Solar Cells
摘要： All-polymer solar cells (all-PSCs) are proven to possess outstanding thermal and mechanical stabilities. However, concurrently achieving appropriate phase-separated pattern, efficient charge transportation, and adequate charge transfer between donor and acceptor components is still a challenge, and thus, only a few polymer-polymer BHJ blends have yielded BHJ device PCEs >8%. Generally, polymer backbone substitutions may have a direct influence on the device performance. Thus, this report examines a set of wide bandgap polymer donor analogues composed of thienothiophene (TT) or thiazolothiazole (TTz) motif, and their all-PSC device performance with N2200. Results show that all-PSCs based on the imine-substituted derivative PBDT-TTz exhibit power conversion efficiencies (PCE) as high as 8.4%, which largely outperform the analogue PBDT-TT-based ones with PCEs of only 0.7%. This work reveals that the imine substitution in polymer backbones of PBDT-TTz not only increases the ionization potential (IP) and electron affinity (EA), narrows the optical gap (Eopt), but also has significantly impacts on the BHJ film morphologies. PBDT-TTz:N2200 BHJ blends present better miscibility, suppressed phase separation, much stronger crystallinity, and face-on ordering, which are contributed to efficient exciton dissociation, charge transportation, and therefore, high-efficiency in all-PSCs. This study demonstrates that the imine-substituted polymers composed of TTz motif, which can be easily synthesized through a facile two-step procedure, are a promising class of wide bandgap polymer donors for efficient all-PSCs.
关键词： Imine substitution,All-polymer solar cells,Thiazolothiazole,Wide bandgap polymer donors,BHJ film morphologies
更新于2025-09-12 10:27:22
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PBDB-T and its derivatives: A family of polymer donors enables over 17% efficiency in organic photovoltaics
摘要： Due to the advantages such as being low cost, light weight, and flexible as well as having low toxicity, organic solar cells (OSCs) have attracted extensive interest. The field of OSCs progressed dramatically after the emergence of non-fullerene small molecule acceptors. In addition to the development of these acceptor materials, a key driver in the rapid progress of OSC research was the introduction of the PBDB-T polymer and its derivatives. In this review, we first give a brief overview of the structural features of PBDB-T congeners and the strategies used to design these polymers. The interesting aggregation effects of PBDB-T congeners in solution and solid-states are highlighted. Recent advances in the morphological understanding OSCs based on PBDB-T congeners are discussed using selected examples. In addition, the versatile applications of PBDB-T congeners in OSC devices, including interfacially modified binary, ternary and tandem devices, are also summarized. Importantly, we assess the energy loss and provide a meta-analysis of a library of high-performance PBDB-T type polymers, which are compared with other types of conjugated polymers. Finally, the remaining questions and the prospects of these exciting polymers are suggested.
关键词： organic solar cells,non-fullerene acceptors,photovoltaic performance,PBDB-T,polymer donors
更新于2025-09-12 10:27:22