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π–π Stacking Distance and Phase Separation Controlled Efficiency in Stable All-Polymer Solar Cells
摘要： The morphology of the active layer plays a crucial role in determining device performance and stability for organic solar cells. All-polymer solar cells (All-PSCs), showing robust and stable morphologies, have been proven to give better thermal stability than their fullerene counterparts. However, outstanding thermal stability is not always the case for polymer blends, and the limiting factors responsible for the poor thermal stability in some All-PSCs, and how to obtain higher efficiency without losing stability, still remain unclear. By studying the morphology of poly [2,3-bis (3-octyloxyphenyl) quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl](TQ1)/poly[4,8-bis[5-(2-ethylhexyl)-2-thienyl]benzo[1,2-b:4,5-b′]dithiophene-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl]] (PCE10)/PNDI-T10 blend systems, we found that the rearranged molecular packing structure and phase separation were mainly responsible for the poor thermal stability in devices containing PCE10. The TQ1/PNDI-T10 devices exhibited an improved PCE with a decreased π–π stacking distance after thermal annealing; PCE10/PNDI-T10 devices showed a better pristine PCE, however, thermal annealing induced the increased π–π stacking distance and thus inferior hole conductivity, leading to a decreased PCE. Thus, a maximum PCE could be achieved in a TQ1/PCE10/PNDI-T10 (1/1/1) ternary system after thermal annealing resulting from their favorable molecular interaction and the trade-off of molecular packing structure variations between TQ1 and PCE10. This indicates that a route to efficient and thermal stable All-PSCs can be achieved in a ternary blend by using material with excellent pristine efficiency, combined with another material showing improved efficiency under thermal annealing.
关键词： morphology,device stability,crystallinity,all-polymer solar cells,thermal annealing,molecular packing structure
更新于2025-09-19 17:13:59
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Optimizing the Phase-Separated Domain Size of the Active Layer via Sequential Crystallization in All-Polymer Solar Cells
摘要： Proper domain size of the active layer plays a key role in determining the exciton dissociation and charge transport in all polymer solar cells (all-PSCs). However, fine-tuning the domain size remains challenging due to low glass transition temperature and negligible mixing entropy in polymer blends. Herein, we systematically studied the influence of “crystallization kinetics” on the domain size and proposed that if donor and acceptor crystallize simultaneously, it is prone to form large domain size; while if sequential crystallization of donor and acceptor occurs, a fine phase separation structure with proper domain size can be obtained. Taking PBDB-T/PNDI blends for instance, the domain size was decreased by using sequential crystallization, meanwhile, the crystallinity and molecular orientation were optimized as well, boosting the power conversion efficiency (PCE) from 6.55% to 7.78%. This work provides a novel way to finely tune the heterojunction phase separation structures.
关键词： domain size,crystallization kinetics,sequential crystallization,all-polymer solar cells,phase separation
更新于2025-09-19 17:13:59
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Exploring a fused 2-(thiophen-2-yl)thieno[3,2-b]thiophene (T-TT) building block to construct n-type polymer toward high performance all-polymer solar cells
摘要： In the field of all-polymer solar cells (all-PSCs), exploring new electron-donating units (D) to match with electron-accepting units (A) is an important subject to promote the performance of D-A type polymer acceptors. Herein, we developed a fused D unit 2-(thiophen-2-yl)thieno[3,2-b]thiophene (T-TT) derivated from the famous 2-(2-(thiophen-2-yl)vinyl)thiophene (TVT) unit. With classical naphthalene diimide (NDI) as A unit, the new D-A polymer PNDI-T-TT exhibits enhanced absorption coefficient, electron mobility and miscibility with donor polymer in comparison with the analogous PNDI-TVT polymer. These advantages can be attributed to the enlarged conjugation and reduced rotamers due to the fused T-TT unit, leading to stronger intermolecular interaction. When blending with the donor polymer PBDB-T, both NDI-based polymers can form better interpenetrating nanostructures than the corresponding blend films with donor polymer J71. Finally, PBDB-T:PNDI-T-TT device obtains a power conversion efficiency (PCE) of 6.1%, which is much higher than that of PBDB-T:PNDI-TVT device (4.24%). These results demonstrate that n-type polymer based on fused T-TT unit can ameliorate the absorption coefficient, molecular aggregation and charge carrier mobility and consequently achieve improved photovoltaic performance in comparison with classic TVT unit.
关键词： All-polymer solar cells,2-(2-(thiophen-2-yl)vinyl)thiophene,PBDB-T,naphthalene diimide,photovoltaic
更新于2025-09-19 17:13:59
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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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Insight into the Efficiency and Stability of All-Polymer Solar Cells Based on Two 2D-Conjugated Polymer Donors: Achieving High Fill Factor of 78%
摘要： Achieving high fill factor (FF) is a great challenge for the all polymer solar cells (all-PSCs) since the FF can be influenced by numerous complicated factors. In this work, two medium bandgap 2D-conjugated copolymers J61 and J71 with varied side chains were utilized as donor to construct efficient all-PSCs with the typical electron-withdrawing polymer N2200 as acceptor. Eventually, moderate photovoltaic performance was obtained for J61:N2200 device with power conversion efficiency (PCE) of 6.58% and FF of 60.18%. While the J71:N2200-based all-PSCs delivered an outstanding PCE of 9.31% with an unprecedented FF of 78.00%. To the best of our knowledge, such an FF of 78% represents a record value for binary all-PSCs systems, which demonstrates that the all-PSCs can realize excellent FF comparable to other PSCs systems. The favorable blends morphology, molecular orientation, balanced charge transport and suppressed recombination together contributed to the remarkable photovoltaic performance of J71:N2200 devices. In addition, relatively weak thickness-dependence of photovoltaic property and excellent long-term device stabilities (in N2 and air, respectively) were observed for the J71:N2200 all-PSCs. These results reveal that J71 with trialkylsilyl side chains is a promising polymer donor candidate for developing high performance all-PSCs for future practical application.
关键词： high efficiency,fill factor,stability,all-polymer solar cells,donor
更新于2025-09-19 17:13:59
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Effect of polymer donor aggregation on active layer morphology of amorphous polymer acceptor-based all-polymer solar cells
摘要： Most of polymer acceptors for all-polymer solar cells (all-PSCs) are semi-crystalline. Amorphous polymer acceptors containing B←N unit represent a new kind of acceptor materials and possess unique phase separation behaviours in all-PSCs. In this work, to study their phase separation morphology and all-PSC device performance, we select three polymer donors with identical polymer backbone but different side chains to blend with an amorphous polymer acceptor (rr-PBN). Among the three polymer donors, J91 exhibits the strongest aggregation tendency in solution and moderate crystallinity in thin film. The J91:rr-PBN blend shows the most optimal phase separation morphology and the best all-PSC device performance. In comparison, J51 shows the least aggregation tendency in solution and the highest crystallinity in thin film. The all-PSC device of J51:rr-PBN blend exhibits sub-optimal active layer morphology and poor photovoltaic performance. These results indicate that the aggregation tendency in solution of polymer donor is the dominant factor in the phase separation of semi-crystalline polymer donor/amorphous polymer acceptor blend in all-PSCs.
关键词： crystallinity,morphology,all-polymer solar cells,aggregation in solution,phase separation
更新于2025-09-19 17:13:59
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Importance of Device Structure and Interlayer Design in Storage Stability of Naphthalene Diimide-based All-Polymer Solar Cells
摘要： While excellent thermal and mechanical stabilities of all-polymer solar cells (all-PSC) have been demonstrated, the storage stability of all-PSCs has rarely been studied. In this paper, the storage stability of all-PSCs is systematically investigated and compared to fullerene-based polymer solar cells (PCBM-PSCs). We identify that the efficient inverted type all-PSCs made with a molybdenum oxide (MoO3) anode interfacial layer can exhibit degradation over short periods of storage even under inert nitrogen-filled and dark conditions, while the control inverted PCBM-PSCs containing the same polymer donor (PDs) are relatively more stable. To elucidate the origin of the poor storage stability, morphological and electrical properties of all-PSCs are investigated. We reveal that the work function of MoO3 is largely changed during the storage because of the interaction between MoO3 and the underneath naphthalene dimide (NDI)-based PAs. This causes unfavorable energy-level alignment in devices, resulting in increased charge recombination and deteriorated charge collecting efficiency. To resolve this issue, we propose two effective strategies: i) introducing a passivation layer to physically separate the NDI-based PAs and MoO3, and ii) replacing MoO3 with an efficient polymer interlayer. We prove that the modified all-PSCs not only exhibit the excellent storage stability with high power conversion efficiency for more than 45 days, but also show high air-stability even without encapsulation. Our findings provide better understanding of the storage stability of all-PSCs and suggest future guidelines for efficient and burn-in free all-PSCs.
关键词： stability,burn-in degradation,all-polymer solar cells,storage lifetime,interlayers,naphthalene diimide polymers
更新于2025-09-16 10:30:52
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Synergistic effect of processing solvent and additive for the production of efficient all-polymer solar cells
摘要： Ideal morphological features are of particular importance to produce high performance all-polymer solar cells (all-PSCs), in which the active blends generally involve unfavorable phase separation due to the complicated intermixing. Developing suitable processing solvent and additive is an effective and versatile approach to manipulate the blends morphology. This study demonstrates the synergistic effect of processing solvent and additive to the photovoltaic performances of all-PSCs composed of a conjugated copolymer J71 donor and typical N2200 acceptor. The low boiling point chloroform (CF) solvent combined with 1% 1,8-diiodoctane (DIO) additive was identified as the optimal processing condition to treat the J71:N2200 blends. Consequently, the all-PSCs casting from CF + 1% DIO achieved an outstanding efficiency of 9.34% with an ultrahigh fill factor of 77.86%, which is among the top values for current all-PSCs systems. Owing to the low JSC, just a moderate efficiency of 7.28% was obtained for the device from chlorobenzene (CB) + 1% DIO processing despite of its high FF. The electron microscopic tests revealed that the CF was superior to CB solvent to obtain uniform morphologies and the addition of DIO additive could further generate more favorable phase separation and domain size. Moreover, the results of charge generation, transport, and recombination analysis correlate well with the remarkable photovoltaic properties. Our results highlight the critical significance of selecting appropriate processing solvent and additive to pursue high performing all-PSCs.
关键词： all-polymer solar cells,processing solvent,morphology,additive,photovoltaic performance
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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Aqueous-Soluble Naphthalene Diimide-Based Polymer Acceptors for Efficient and Air-Stable All-Polymer Solar Cells
摘要： Aqueous-processed all-polymer solar cells (aq-APSCs) are reported for the first time by developing a series of water/ethanol-soluble naphthalene diimide (NDI)-based polymer acceptors P(NDIDEG-T), P(NDITEG-T), and P(NDITEG-T2). Polymer acceptors are designed by using the backbones of NDI-bithiophene and NDI-thiophene in combination with non-ionic hydrophilic oligoethylene glycol (OEG) side chains that facilitate processability in water/ethanol mixtures. All three polymers exhibit sufficient solubility (20-50 mg mL?1) in the aqueous medium. The P(NDIDEG-T) polymer with shorter OEG side chains is the most crystalline with the highest electron mobility, enabling the fabrication of efficient aq-APSCs with the maximum power conversion efficiency (PCE) of 2.15%. Furthermore, these aq-APSCs are fabricated under ambient atmosphere by taking advantage of the eco-friendly aqueous process and, importantly, the devices exhibit outstanding air-stability without any encapsulation, as evident by maintaining more than 90% of the initial PCE in air after 4 days. According to a double cantilever beam test, the interfacial adhesion properties between the active layer and electron/hole transporting layers were remarkably improved by incorporating the hydrophilic OEG-attached photoactive layer, which hinders the delamination of the constituent layers and prevents the increase of series resistance, ultimately leading to enhanced durability under ambient conditions. The combination of increased device stability and minimized environmental impact of these aq-APSCs demonstrates them to be worthy candidates for continued development of scalable polymer solar cells.
关键词： eco-friendly solution process,aqueous process,air-stability,all-polymer solar cells,oligoethylene glycol (OEG) side chain
更新于2025-09-12 10:27:22