| 1. |
- Duan, Chunhui, et al.
(författare)
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Improving Performance of All-Polymer Solar Cells Through Backbone Engineering of Both Donors and Acceptors
- 2018
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Ingår i: Solar RRL. - : Wiley. - 2367-198X. ; 2:12
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Tidskriftsartikel (refereegranskat)abstract
- All-polymer solar cells (APSCs), composed of semiconducting donor and acceptor polymers, have attracted considerable attention due to their unique advantages compared to polymer-fullerene-based devices in terms of enhanced light absorption and morphological stability. To improve the performance of APSCs, the morphology of the active layer must be optimized. By employing a random copolymerization strategy to control the regularity of the backbone of the donor polymers (PTAZ-TPDx) and acceptor polymers (PNDI-Tx) the morphology can be systematically optimized by tuning the polymer packing and crystallinity. To minimize effects of molecular weight, both donor and acceptor polymers have number-average molecular weights in narrow ranges. Experimental and coarse-grained modeling results disclose that systematic backbone engineering greatly affects the polymer crystallinity and ultimately the phase separation and morphology of the all-polymer blends. Decreasing the backbone regularity of either the donor or the acceptor polymer reduces the local crystallinity of the individual phase in blend films, affording reduced short-circuit current densities and fill factors. This two-dimensional crystallinity optimization strategy locates a PCE maximum at highest crystallinity for both donor and acceptor polymers. Overall, this study demonstrates that proper control of both donor and acceptor polymer crystallinity simultaneously is essential to optimize APSC performance.
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| 2. |
- Hu, Yuanyuan, et al.
(författare)
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Correlation of Molecular Structure and Charge Transport Properties: A Case Study in Naphthalenediimide–Based Copolymer Semiconductors
- 2018
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Ingår i: Advanced Electronic Materials. - : Wiley. - 2199-160X .- 2199-160X. ; 4:8
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Tidskriftsartikel (refereegranskat)abstract
- Recent development of donor–acceptor (D–A) structure copolymers has led to the remarkable enhancement of mobility over 10 cm2(V s)−1in organic semiconductors. Despite these achievements, a thorough understanding of the correlation between molecular structure and charge transport properties is still not achieved. With this goal in mind, the electrical properties of three copolymers based on the naphthalenediimide (NDI) acceptor with different donor units are compared, and the effect of increasing donor length on the electronic structure of semiconductors and the resulting charge transport performance is studied. Structural and morphological characterizations are done to reveal the macro transport properties of the semiconductor films. Then, electrical measurements of the field-effect transistors at variable temperatures are carried out to probe the charge transport property of the semiconductor films. Overall, it is found that the increasing of the donor length from one to three thiophene units would reduce the energetic disorder in the semiconductor films. Meanwhile, the electron cloud overlap between acceptor units would be weakened, which is detrimental to electron transport. Thus, a trading-off between energetic disorder and electron cloud overlap is critical for achieving high mobility in this NDI–based copolymer system.
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| 3. |
- Li, Zhaojun, 1989, et al.
(författare)
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9.0% power conversion efficiency from ternary all-polymer solar cells
- 2017
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Ingår i: Energy and Environmental Science. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 10:10, s. 2212-2221
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Tidskriftsartikel (refereegranskat)abstract
- Integration of a third component into a single-junction polymer solar cell (PSC) is regarded as an attractive strategy to enhance the performance of PSCs. Although binary all-polymer solar cells (all-PSCs) have recently emerged with compelling power conversion efficiencies (PCEs), the PCEs of ternary all-PSCs still lag behind those of the state-of-the-art binary all-PSCs, and the advantages of ternary systems are not fully exploited. In this work, we realize high-performance ternary all-PSCs with record-breaking PCEs of 9% and high fill factors (FF) of over 0.7 for both conventional and inverted devices. The improved photovoltaic performance benefits from the synergistic effects of extended absorption, more efficient charge generation, optimal polymer orientations and suppressed recombination losses compared to the binary all-PSCs, as evidenced by a set of experimental techniques. The results provide new insights for developing high-performance ternary all-PSCs by choosing appropriate donor and acceptor polymers to overcome limitations in absorption, by affording good miscibility, and by benefiting from charge and energy transfer mechanisms for efficient charge generation.
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| 4. |
- Li, Zhaojun, 1989, et al.
(författare)
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High-performance all-polymer solar cells based on fluorinated naphthalene diimide acceptor polymers with fine-tuned crystallinity and enhanced dielectric constants
- 2018
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Ingår i: Nano Energy. - : Elsevier BV. - 2211-2855. ; 45, s. 368-379
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Tidskriftsartikel (refereegranskat)abstract
- Growing interests have been devoted to the synthesis of polymer acceptors as alternatives to fullerene derivatives to realize high-performance and stable all-polymer solar cells (all-PSCs). So far, one of the key factors that limit the performance of all-PSCs is low photocurrent density (normally < 14 mA/cm 2 ). One potential solution is to improve the dielectric constants (ε r ) of polyme r :polymer blends, which tend to reduce the binding energy of excitons, thus boosting the exciton dissociation efficiencies. Nevertheless, the correlation between ε r and photovoltaic performance has been rarely investigated for all-PSCs. In this work, five fluorinated naphthalene diimide (NDI)-based acceptor polymers, with different content of fluorine were synthesized. The incorporation of fluorine increased the ε r of the acceptor polymers and blend films, which improved the charge generation and overall photocurrent of the all-PSCs. As a result, the PTB7-Th:PNDI-FT10 all-PSC attained a high power conversion efficiency (PCE) of 7.3% with a photocurrent density of 14.7 mA/cm 2 , which surpassed the values reported for the all-PSC based on the non-fluorinated acceptor PNDI-T10. Interestingly, similarly high photovoltaic performance was maintained regardless of a large variation of donor:acceptor ratios, which revealed the good morphological tolerance and the potential for robust production capability of all-PSCs.
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| 5. |
- Li, Zhaojun, 1989, et al.
(författare)
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High Performance All-Polymer Solar Cells by Synergistic Effects of Fine-Tuned Crystallinity and Solvent Annealing.
- 2016
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 138:34, s. 10935-44
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Tidskriftsartikel (refereegranskat)abstract
- Growing interests have been devoted to the design of polymer acceptors as potential replacement for fullerene derivatives for high-performance all polymer solar cells (all-PSCs). One key factor that is limiting the efficiency of all-PSCs is the low fill factor (FF) (normally
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| 6. |
- Li, Zhaojun, 1989, et al.
(författare)
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High-Performance and Stable All-Polymer Solar Cells Using Donor and Acceptor Polymers with Complementary Absorption
- 2017
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Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6832 .- 1614-6840. ; 7:14
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Tidskriftsartikel (refereegranskat)abstract
- To explore the advantages of emerging all-polymer solar cells (all-PSCs), growing efforts have been devoted to developing matched donor and acceptor polymers to outperform fullerene-based PSCs. In this work, a detailed characterization and comparison of all-PSCs using a set of donor and acceptor polymers with both conventional and inverted device structures is performed. A simple method to quantify the actual composition and light harvesting contributions from the individual donor and acceptor is described. Detailed study on the exciton dissociation and charge recombination is carried out by a set of measurements to understand the photocurrent loss. It is unraveled that fine-tuned crystallinity of the acceptor, matched donor and acceptor with complementary absorption and desired energy levels, and device architecture engineering can synergistically boost the performance of all-PSCs. As expected, the PBDTTS-FTAZ:PNDI-T10 all-PSC attains a high and stable power conversion efficiency of 6.9% without obvious efficiency decay in 60 d. This work demonstrates that PNDI-T10 can be a potential alternative acceptor polymer to the widely used acceptor N2200 for high-performance and stable all-PSCs.
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| 7. |
- Li, Zhaojun, 1989, et al.
(författare)
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High-photovoltage all-polymer solar cells based on a diketopyrrolopyrrole-isoindigo acceptor polymer
- 2017
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 5:23, s. 11693-11700
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we synthesized and characterized two new n-type polymers PTDPP-PyDPP and PIID-PyDPP. The former polymer is composed of pyridine-flanked diketopyrrolopyrrole (PyDPP) and thiophene-flanked diketopyrrolopyrrole (TDPP). The latter polymer consists of PyDPP and isoindigo (IID). PIID-PyDPP exhibits a much higher absorption coefficient compared to the widely used naphthalene diimide (NDI)-based acceptor polymers, and its high-lying LUMO level affords it to achieve a high open-circuit voltage (Voc). As a result, an all-polymer solar cell (all-PSC) fabricated from a high band gap polymer PBDTTS-FTAZ as the donor and PIID-PyDPP as the acceptor attained a high Voc of 1.07 V with a power conversion efficiency (PCE) of 4.2%. So far, it has been one of the highest PCEs recorded from all-PSCs using diketopyrrolopyrrole (DPP)-based acceptors. Gratifyingly, no obvious PCE decay was observed in two weeks, unraveling good stability of the all-PSC. This work demonstrates that the electron-withdrawing PyDPP unit can be a promising building block for new acceptor polymers in all-PSCs.
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| 8. |
- Li, Zhaojun, 1989
(författare)
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Synthesis and Characterization of Acceptor Polymers for All-Polymer Solar Cells and Photodetectors
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The development of polymer semiconductors has become an important topic due to its advantages of low cost, easy fabrication, light weight, and capability to fabricate flexible large-area devices. For example, as the need for new clean energy sources is increasing, polymer solar cells (PSCs) are being developed rapidly and becoming a promising alternative to silicon solar cells. This thesis focuses on the applications of polymer semiconductors in two active fields of polymeric optoelectronics: PSCs and polymer photodetectors (PPDs). Heretofore, PSCs and PPDs were fabricated commonly using a blend of a conjugated polymer and a fullerene derivative as the active layer. Despite the wide use of fullerene derivatives, their limitations such as low absorption, morphological instability, and high costs, created a strong need to develop new acceptor materials. Therefore, all-polymer solar cells (all-PSCs) and allpolymer photodetectors (all-PPDs) based on a blend of conjugated polymers acting as both electron donor and acceptor are being actively pursued. We have made concerted efforts to prepare high-performance all-PSCs and all-PPDs, by specifically modifying the acceptor molecular structure, and rationally choosing suitable donor and acceptor combinations. This aspect of our work had two main facets: * Material synthesis: the design, synthesis and characterization of novel acceptor polymers. * Device engineering: the fabrication, optimization and characterization of all-PSCs and all-PPDs. Our efforts in the design of novel acceptor polymers focused on crystallinity and energy level engineering via structural modifications like backbone and sidechain modulation. Also, a comprehensive comparison of the characteristic functional properties of acceptor polymers was undertaken. Binary devices using donor and acceptor polymers with complementary absorption or suitable energy level offset, and ternary devices were studied to further improve the performance of all- PSCs. High efficiencies of 8.0% and 9.0% are achieved for binary all-PSCs and ternary all-PSCs, respectively. Additionally, high-performance all-PPDs exhibiting low dark current density (Jd) and high responsivity (R) under -5 V bias were demonstrated. Based on the results presented herein, we are now moving closer to understanding the correlation between the polymer structure, blend morphology, and device performance. This thesis also provides a guideline for developing all-PSCs and all-PPDs with improved performance.
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| 9. |
- Lin, Y. B., et al.
(författare)
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Energy-effectively printed all-polymer solar cells exceeding 8.61% efficiency
- 2018
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Ingår i: Nano Energy. - : Elsevier BV. - 2211-2855. ; 46, s. 428-435
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Tidskriftsartikel (refereegranskat)abstract
- All-polymer solar cells (all-PSCs) have attracted tremendous attention in the past few years due to their unique advantages. However, up to now most of high-efficiency all-PSCs are processed by spin-coating with complicated post treatment processes, which is ill-suited to a large-area roll-to-roll (R2R) technique. In this work, high-efficiency all-PSCs based on PTB7-Th and PNDI-T10 are achieved by one of R2R compatible printing techniques, i.e. doctor-blading, without any annealing treatment. It was found that incorporating an additive into all polymer blends solution can prolong the drying time of all polymer nanocomposites from 120 to 1000 s to form a better bulk heterojunction morphology and a higher crystallinity, which thus reduce charge recombination and show much better electrical impedance spectroscopy parameters. Record-breaking power conversion efficiencies (PCEs) of 8.61% and high fill factors (FF) of 0.71 are achieved by doctor-blading under an extremely process-simple and energy-effective conditions. Moreover, large-area (2.03 cm 2 ) flexible ITO-free all-PSCs by doctor-blading with record-breaking PCEs of 6.65% and FF of 0.65 are realized, which are much higher than conventional fullerene-based ones under the same condition, demonstrating that all-PSCs are more suitable for the flexible device structure and have a bright future towards practical application with R2R manufacture.
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| 10. |
- Xu, Xiaofeng, 1984, et al.
(författare)
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8.0% Efficient All-Polymer Solar Cells with High Photovoltage of 1.1 V and Internal Quantum Efficiency near Unity
- 2018
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Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6832 .- 1614-6840. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- In very recent years, growing efforts have been devoted to the development of all-polymer solar cells (all-PSCs). One of the advantages of all-PSCs over the fullerene-based PSCs is the versatile design of both donor and acceptor polymers which allows the optimization of energy levels to maximize the open-circuit voltage (Voc). However, there is no successful example of all-PSCs with both high Voc over 1 V and high power conversion efficiency (PCE) up to 8% reported so far. In this work, a combination of a donor polymer poly[4,8-bis(5-(2-octylthio)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl-alt-(5-(2-ethylhexyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione)-1,3-diyl] (PBDTS-TPD) with a low-lying highest occupied molecular orbital level and an acceptor polymer poly[[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-thiophene-2,5-diyl] (PNDI-T) with a high-lying lowest unoccupied molecular orbital level is used, realizing high-performance all-PSCs with simultaneously high Voc of 1.1 V and high PCE of 8.0%, and surpassing the performance of the corresponding PC71BM-based PSCs. The PBDTS-TPD:PNDI-T all-PSCs achieve a maximum internal quantum efficiency of 95% at 450 nm, which reveals that almost all the absorbed photons can be converted into free charges and collected by electrodes. This work demonstrates the advantages of all-PSCs by incorporating proper donor and acceptor polymers to boost both Voc and PCEs.
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