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Cyclopentadithiophene cored A-π-D-π-A non-fullerene electron acceptor in ternary polymer solar cells to extend the light absorption up to 900?nm
摘要： Conjugated small molecular non-fullerene electron acceptors (NFA) are considered as one of the critical materials for achieving high performance and low cost of polymer solar cells, and received much attention in the last few years. However, most of the NFAs are based on large fused π-aromatic core, which requires complicate synthesis efforts. In addition, the relatively weak light absorption limited to 800 nm of most the NAFs limits the energy harvesting capability of the solar cells. In this paper, we report an A-π-D-π-A type molecule cored with a cyclopentadithiophene unit, which can be easily synthesized in two steps from commercially available starting materials. This compound shows a broad absorption up to 900 nm in thin solid film, which is ascribed to the relatively high highest occupied molecular orbital (HOMO) energy level as confirmed by cyclic voltammery and theoratical calculation. Application of the compound in polymer solar cells was also investigated both in binary and in ternary systems. The optimized power conversion efficiency (PCE) in binary solar cell with PTB7-Th as donor is 5.76% with an open circuit voltage (VOC) of 0.838 V, a short circuit current (JSC) of 14.81 mA/cm2 and a fill factor (FF) of 46.4%. In the ternary solar cells which includes a second acceptor, PC71BM, the highest PCE achieved is 9.39% with a VOC of 0.803 V, a JSC of 19.01 mA/cm2, a FF of 61.6%, which is over 20% enhancement compared to the PTB7-Th:PC71BM system (PCE of 7.58%). This work develops a simple small molecule non-fullerene acceptor which can largely enhance the photo response in near infrared region to improve the performance of fullerene based organic solar cell.
关键词： Light absorption,Non-fullerene electron acceptor,Cyclopentadithiophene,Ternary systems,Polymer solar cells
更新于2025-09-12 10:27:22
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Wide-Band-Gap Phthalimide-Based D-π-A Polymers for Nonfullerene Organic Solar Cells: The Effect of Conjugated π-Bridge from Thiophene to Thieno[3,2- <i>b</i> ]thiophene
摘要： Conjugated polymers with D-π-A backbone structures have been intensively investigated and have largely promoted the rapid progress of organic solar cells (OSCs). However, as one of the simplest electron-accepting (A) units, phthalimide (PhI), only attracts less attention to construct promising D-π-A photovoltaic polymers in OSC community. Thus the correlations between the chemical structure-optoelectronic properties-photovoltaic performance need to be systematically investigated. Here, we combined the PhI moiety with the electron-donating (D) unit benzodithiophene (BDT) to synthesize two D-π-A copolymers PE80 and PE81, where the π-bridge corresponds to the thiophene (T) and thieno[3,2-b]thiophene (TT) respectively. When blended with a low bandgap (Eg=1.33 eV) non-fullerene acceptor Y6, PE81 achieved a power conversion efficiency (PCE) of 10.21% with an open circuit voltages (VOC) of 0.90 V, which are much higher than those of PE80:Y6 device (PCE = 4.11% and VOC = 0.88 V). Our results indicate that PhI is also a promising electron-deficient unit to construct photovoltaic polymers and using TT π-bridge is simple strategy to improve the photovoltaic performance of D-π-A polymers.
关键词： non-fullerene organic solar cells,D-π-A backbone,Conjugated polymers,thieno[3,2-b]thiophene,phthalimide
更新于2025-09-12 10:27:22
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Scalable fabrication of organic solar cells based on non-fullerene acceptors
摘要： Organic solar cells have recently experienced a substantial leap in power conversion efficiency, in part driven by formulations with new non-fullerene acceptors. This has brought the technology past the psychologically important mark of 15 % efficiency for unscaled laboratory devices, and the results are stimulating another burst of research activity. Whether this will propel the technology into a viable commercial contender has yet to be determined, but to realize the potential of organic solar cells for utility scale application, fabrication using scalable processing techniques has to be demonstrated - otherwise, the passing of the 15 % mark will eventually leave no more lasting impact than what the passing of the 10 % mark did. Thus, addressing the scaling lag between the 15 % cell efficiencies of lab-scale devices on rigid glass substrates fabricated using non-scalable techniques and the 7 % efficiencies of scalably fabricated devices on flexible substrates is key. Here, we discuss the concept of scalability and give an account of the literature on non-fullerene acceptor devices fabricated with scalable methods and materials. On the basis of this, we identify three crucial focus points for overcoming the lab-to-fab challenge: i) dual temperature control, i.e. simultaneous control of the ink and substrate temperatures during deposition, ii) systematic in situ morphology studies of active layer inks with new, green solvent formulations during continuous deposition, and iii) development of protocols for continuous solution processing of smooth, transparent interfacial layers with efficient charge transfer to the active layer. Combining these efforts and in general accompanying such studies with stability analyses and fabrication of large-area, scalably processed devices are believed to accelerate the relevance of organic solar cells for large-scale energy supply.
关键词： roll-to-roll processing,organic solar cells,non-fullerene acceptors,power conversion efficiency,scalable fabrication
更新于2025-09-12 10:27:22
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Difluorobenzoxadiazole-based conjugated polymers for efficient non-fullerene polymer solar cells with low voltage loss
摘要： Two donor-acceptor (D-A) conjugated copolymers based on difluorobenzoxadiazole (ffBX) and oligothiophenes, i.e., PffBX-2T and PffBX-TT, were designed and synthesized for polymer solar cells (PSCs). Compared to the polymers based on difluorobenzothiadiazole (ffBT) units, the two ffBX-based polymers presented identical optical bandgaps (~1.62 eV), but lower highest occupied molecular orbital (HOMO) energy levels. Owing to the down-shifted HOMO levels, the PSCs based on PffBX-2T and PffBX-TT showed lower voltage loss, and the open-circuit voltage (Voc) was ~0.1 V higher than that of the devices with the ffBT-based polymer. As a result, higher photovoltaic performance was achieved for the devices based on the ffBX-based polymers. The power conversion efficiencies (PCEs) of the non-fullerene PSCs with PffBX-2T and PffBX-TT as the donor were 8.72% and 10.12%, respectively. The superior device performance of PffBX-TT resulted from the efficient exciton dissociation and charge transport as well as weak charge recombination, which could be ascribed to the favorable face-on packing of the conjugated backbones and the desired morphology in the blend film. Our study demonstrates that difluorobenzoxadiazole is a promising building block for constructing conjugated polymers for high-performance non-fullerene PSCs.
关键词： voltage loss,difluorobenzoxadiazole,alkylthiophene side chains,non-fullerene polymer solar cells
更新于2025-09-12 10:27:22
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Di‐fluorinated Oligothiophenes for High‐Efficiency All‐Small‐Molecule Organic Solar Cells: Positional Isomeric Effect of Fluorine Substitution on Performance Variations
摘要： Three symmetrically di-fluorinated organic semiconductors (namely D5T2F-P, D5T2F-S, and D5T2F-T) containing rhodanine-flanked pentathiophene structures are synthesized and used as donors in all-small-molecule organic solar cells (ASM-OSCs) prepared with the small-molecule acceptor 2,2'-((2Z,2'Z)-((4,4,9,9-tetrahexyl-4,9-dihydro-s-indaceno[1,2-b:5,6-b']dithiophene-2,7-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (IDIC-4F). The different substitutional positions of the fluorine atoms (-F) in the conjugated backbone of the donor molecule leads to various material and photovoltaic properties being exhibited. Among the three isomers, the centrally-fluorinated D5T2F-P exhibits a redshifted absorption spectrum, downshifted highest occupied molecular orbital (HOMO) energy level, and improved miscibility with IDIC-4F in the blend films, all of which result in superior device performance. The power conversion efficiency (PCE) of the ASM-OSCs based on D5T2F-P:IDIC-4F reaches the impressive value of 9.36% with an open-circuit voltage (VOC) value of 0.86 V and a short-circuit current density (JSC) value of 16.94 mA/cm2, while those of D5T2F-S (6.11%) and D5T2F-T (5.42%) are much lower. In comparison, an ASM-OSC based on the non-fluorinated analogue DRCN5T fabricated under the same conditions exhibits poorer performance (8.03% with IDIC-4F), revealing a 16% enhancement in PCE achieved through backbone fluorination. To the best of our knowledge, the PCE of 9.36% is one of the highest efficiencies of oligothiophene-based ASM-OSCs reported in the literature to date.
关键词： organic solar cells,binding energy,small molecule donors,fluorination,non-fullerene
更新于2025-09-12 10:27:22
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Effects of oxygen atoms introduced at different positions of non-fullerene acceptors on performance of organic solar cells with poly(3-hexylthiophene)
摘要： With the development of large-area fabrication technologies for organic solar cells (OSCs), poly(3-hexylthiophene) (P3HT) is the best chioce as photovoltaic donor polymer becasue it can be easily synthesized in the scale of kilogram with low cost. However, non-fullerene acceptors (NFAs) matching with P3HT for high performance OSCs are very rare. Herein, by introducing oxygen atoms into the side chains or fused-ring core of indaceno[1,2-b:5,6-b’]dithiophene (IDT), we synthesized two new A2-A1-D-A1-A2 type NFAs, where benzotriazole (BTA) and 2-(1,1-dicyanomethylene)rhodanine (RCN) were used as bridged A1 and terminal A2 respectively. The final NFAs, named as BTA43 and BTA53, show wider absorption spectra and enhanced inter-/intra-molecular interaction in comparison with their analogue BTA3 without oxygen atom. The photovoltaic devices based on P3HT:BTA43 and P3HT:BTA53 can achieve the high PCEs of 6.56% and 6.31% respectively, which are obvious higher than that of BTA3 (5.64%). Our results provide a simple and effective strategy to design promising NFAs to pair with classic photovoltaic polymer P3HT.
关键词： molecular engineering,photovoltaic,non-fullerene acceptors,organic solar cells,P3HT
更新于2025-09-12 10:27:22
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A high-performance non-fullerene electron acceptor with bisalkylthiothiophene π-bridges for organic photovoltaics
摘要： A new non-fullerene small molecule acceptor IDT2ST-4F bearing a bisalkylthiothiophene unit as the p-bridge was designed and synthesized, which exhibited a low optical bandgap of 1.43 eV. The optimized organic solar cells based on PBDB-T:IDT2ST-4F gave a high power conversion efficiency (PCE) of 11.43% with a relatively low energy loss of 0.58 eV.
关键词： non-fullerene electron acceptor,power conversion efficiency,organic photovoltaics,bisalkylthiothiophene
更新于2025-09-12 10:27:22
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Efficient polymer solar cells that use conjugated polyelectrolyte with a tetravalent amine-end side chain
摘要： Conjugated polyelectrolyte based on benzotriazole (BT) with tetravalent amine-end side chain and benzothiadiazole (BTz) conjugated alternating repeat units, named PBTBTz-TMAI was initially designed and synthesized. Fullerene- and non-fullerene-based polymer solar cells were fabricated using PBTBTz-TMAI as the cathode interlayer. Consequently, power conversion efficiencies of 8.4% and 10.5% were achieved for the fullerene PTB7:PC71BM-based and non-fullerene PBDB-T:ITIC-based single-junction devices, respectively. The enhanced performance is attributed to the appropriate energy level alignment of the active layer with PBTBTz-TMAI and the efficient electron transfer from the active layer to the cathode electrode.
关键词： cathode interlayer,non-fullerene,tetravalent amine-end,conjugated polyelectrolyte,polymer solar cells
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
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Improved Efficiency in All-Small-Molecule Organic Solar Cells with Ternary Blend of Non-Fullerene Acceptor and Chlorinated and Non-Chlorinated Donors.
摘要： Ternary non-fullerene all-small-molecule organic solar cells (NFSM-OSCs) were developed by incorporating a non-fullerene acceptor (IDIC) and two structurally similar small molecular donors (SM and SM-Cl), where SM-Cl is a novel small molecular donor derived from the reported molecular donor SM. When doping 10% SM-Cl in SM:IDIC binary system, the power conversion efficiency (PCE) of ternary solar cell was dramatically increased from 9.39% to 10.29%. Characterization studies indicated that the two donors tend to form an alloy state, which effectively down-shifted the HOMO energy level of the donor, and thus promoting a higher open-circuit voltage. Interestingly, incorporating a third component (SM-Cl) with lower crystallinity was proven to facilitate the demixing between donors and acceptors, which was in contrary to the traditional findings of enhanced phase separation through incorporation of highly crystalline molecule. Although the morphological modulation had always been a bottleneck issue in NFSM-OSCs, the findings in this work indicated that the modulation on crystallinity deviation between donors and acceptors could be an effective method to further improve the performance of NFSM-OSCs, providing a new perspective on NFSM-OSCs.
关键词： alloy model,non-fullerene all-small-molecule solar cells,chlorinated molecular donor,ternary strategy,crystallinity modulation
更新于2025-09-12 10:27:22