| 1. |
- Liu, Tao, et al.
(författare)
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16% efficiency all-polymer organic solar cells enabled by a finely tuned morphology via the design of ternary blend
- 2021
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Ingår i: Joule. - : CELL PRESS. - 2542-4351. ; 5:4, s. 914-930
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Tidskriftsartikel (refereegranskat)abstract
- A SUMMARY There is an urgent demand for all-polymer organic solar cells (AP-OSCs) to gain higher efficiency. Here, we successfully improve the performance to 16.09% by introducing a small amount of BN-T, a B <- N-type polymer acceptor, into the PM6:PY-IT blend. It has been found that BN-T makes the active layer, based on the PM6:PY-IT:BN-T ternary blend, more crystalline but meanwhile slightly reduces the phase separation, leading to enhancement of both exciton harvesting and charge transport. From a thermodynamic viewpoint, BN-T prefers to reside between PM6 and PY-IT, and the fraction of this fine-tunes the morphology. Besides, a significantly reduced nonradiative energy loss occurs in the ternary blend, along with the coexistence of energy and charge transfer between the two acceptors. The progressive performance facilitated by these improved properties demonstrates that AP-OSCs can possibly comparably efficient with those based on small molecule acceptors, further enhancing the competitiveness of this device type.
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| 2. |
- Hart, Lucy J. F., et al.
(författare)
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Understanding the Role of Triplet-Triplet Annihilation in Non-Fullerene Acceptor Organic Solar Cells
- 2023
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Ingår i: Advanced Energy Materials. - : WILEY-V C H VERLAG GMBH. - 1614-6832 .- 1614-6840. ; 13:36
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Tidskriftsartikel (refereegranskat)abstract
- Non-fullerene acceptors (NFAs) have enabled power conversion efficiencies exceeding 19% in organic solar cells (OSCs). However, the open-circuit voltage of OSCs remains low relative to their optical gap due to excessive non-radiative recombination, and this now limits performance. Here, an important aspect of OSC design is considered, namely management of the triplet exciton population formed after non-geminate charge recombination. By comparing the blends PM6:Y11 and PM6:Y6, it is shown that the greater crystallinity of the NFA domains in PM6:Y11 leads to a higher rate of triplet-triplet annihilation (TTA). This is attributed to the four times larger ground state dipole moment of Y11 versus Y6, which improves the long range NFA out-of-plane ordering. Since TTA converts a fraction of the non-emissive triplet states into bright singlet states, it has the potential to reduce non-radiative voltage losses. Through a kinetic analysis of the recombination processes under 1-Sun illumination, a framework is provided for determining the conditions under which TTA may improve OSC performance. If these could be satisfied, TTA has the potential to reduce non-radiative voltage losses by up to several tens of millivolts.
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| 3. |
- Luo, Zhenghui, et al.
(författare)
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Fine-Tuning Energy Levels via Asymmetric End Groups Enables Polymer Solar Cells with Efficiencies over 17%
- 2020
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Ingår i: Joule. - : CELL PRESS. - 2542-4351. ; 4:6, s. 1236-1247
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Tidskriftsartikel (refereegranskat)abstract
- Generally, it is important to fine-tune the energy levels of donor and acceptor materials in the field of polymer solar cell (PSCs) to achieve a minimal highest occupied molecular orbital (HOMO) energy offset, which yet is still sufficient for charge separation. Based on the high-performance small-molecule acceptor (SMA) of BTP-4F, we modified the end groups of BTP-4F from IC-2F to CPTCN-Cl. It was found that when both end groups were substituted by CPTCN-Cl, the energy level upshift was too large that caused unfavorable energetic alignment, thus poor device performance. By using the strategy of asymmetric end groups, we were able to achieve near optimal energy level match, resulting in higher open-circuit voltage (V-OC) and power conversion efficiency (PCE) compared with those given by the PM6:BTP-4F system. Our strategy can be useful and potentially applied to othermaterial systems for maximizing efficiency of non-fullerene PSCs.
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| 4. |
- Luo, Zhenghui, et al.
(författare)
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Heteroheptacene-based acceptors with thieno[3,2-b]pyrrole yield high-performance polymer solar cells
- 2022
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Ingår i: NATIONAL SCIENCE REVIEW. - : Oxford University Press. - 2095-5138 .- 2053-714X. ; 9:7
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Tidskriftsartikel (refereegranskat)abstract
- Rationally utilizing and developing synthetic units is of particular significance for the design of high-performance non-fullerene small-molecule acceptors (SMAs). Here, a thieno[3,2-b]pyrrole synthetic unit was employed to develop a set of SMAs (ThPy1, ThPy2, ThPy3 and ThPy4) by changing the number or the position of the pyrrole ring in the central core based on a standard SMA of IT-4Cl, compared to which the four thieno[3,2-b]pyrrole-based acceptors exhibit bathochromic absorption and upshifted frontier orbital energy level due to the strong electron-donating ability of pyrrole. As a result, the polymer solar cells (PSCs) of the four thieno[3,2-b]pyrrole-based acceptors yield higher open-circuit voltage and lower energy loss relative to those of the IT-4Cl-based device. What is more, the ThPy3-based device achieves a power conversion efficiency (PCE) (15.3%) and an outstanding fill factor (FF) (0.771) that are superior to the IT-4Cl-based device (PCE = 12.6%, FF = 0.758). The ThPy4-based device realizes the lowest energy loss and the smallest optical band gap, and the ternary PSC device based on PM6:BTP-eC9:ThPy4 exhibits a PCE of 18.43% and a FF of 0.802. Overall, this work sheds light on the great potential of thieno[3,2-b]pyrrole-based SMAs in realizing low energy loss and high PCE. Four heteroheptacene-based acceptors using thieno[3,2-b]pyrrole building block were developed for the first time, and all the four acceptors-based devices realized high performance and low energy loss.
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| 5. |
- Yao, Huatong, et al.
(författare)
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All-Polymer Solar Cells with over 12% Efficiency and a Small Voltage Loss Enabled by a Polymer Acceptor Based on an Extended Fused Ring Core
- 2020
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Ingår i: Advanced Energy Materials. - : WILEY-V C H VERLAG GMBH. - 1614-6832 .- 1614-6840. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Although the field of all-polymer solar cells (all-PSCs) has seen rapid progress in device efficiencies during the past few years, there are limited choices of polymer acceptors that exhibit strong absorption in the near-IR region and achieve high open-circuit voltage (V-OC) at the same time. In this paper, an all-PSC device is demonstrated with a 12.06% efficiency based on a new polymer acceptor (named PT-IDTTIC) that exhibits strong absorption (maximum absorption coefficient: 2.41 x 10(5)cm(-1)) and a narrow optical bandgap (1.49 eV). Compared to previously reported polymer acceptors such as those based on the indacenodithiophene (IDT) core, the indacenodithienothiophene (IDTT) core has further extended fused ring, providing the polymer with extended absorption into the near-IR region and also increases the electron mobility of the polymer. By blending PT-IDTTIC with the donor polymer, PM6, a high-efficiency all-PSC is achieved with a small voltage loss of 0.52 V, without sacrificingJ(SC)and FF, which demonstrates the great potential of high-performance all-PSCs.
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