| 1. |
- Zhang, Jianyun, et al.
(författare)
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Revealing the Critical Role of the HOMO Alignment on Maximizing Current Extraction and Suppressing Energy Loss in Organic Solar Cells
- 2019
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Ingår i: iScience. - : Cell Press. - 2589-0042. ; 19, s. 883-893
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Tidskriftsartikel (refereegranskat)abstract
- For state-of-the-art organic solar cells (OSCs) consisting of a large-bandgap polymer donor and a near-infrared (NIR) molecular acceptor, the control of the HOMO offset is the key to simultaneously achieve small energy loss (Eloss) and high photocurrent. However, the relationship between HOMO offsets and the efficiency for hole separation is quite elusive so far, which requires a comprehensive understanding on how small the driving force can effectively perform the charge separation while obtaining a high photovoltage to ensure high OSC performance. By designing a new family of ZITI-X NIR acceptors (X = S, C, N) with a high structural similarity and matching them with polymer donor J71 forming reduced HOMO offsets, we systematically investigated and established the relationship among the photovoltaic performance, energy loss, and hole-transfer kinetics. We achieved the highest PCEavgs of 14.05 ± 0.21% in a ternary system (J71:ZITI-C:ZITI-N) that best optimize the balance between driving force and energy loss.
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| 2. |
- Zhou, Zichun, et al.
(författare)
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Subtle Molecular Tailoring Induces Significant Morphology Optimization Enabling over 16% Efficiency Organic Solar Cells with Efficient Charge Generation
- 2020
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Ingår i: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095. ; 32:4
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Tidskriftsartikel (refereegranskat)abstract
- Manipulating charge generation in a broad spectral region has proved to be crucial for nonfullerene-electron-acceptor-based organic solar cells (OSCs). 16.64% high efficiency binary OSCs are achieved through the use of a novel electron acceptor AQx-2 with quinoxaline-containing fused core and PBDB-TF as donor. The significant increase in photovoltaic performance of AQx-2 based devices is obtained merely by a subtle tailoring in molecular structure of its analogue AQx-1. Combining the detailed morphology and transient absorption spectroscopy analyses, a good structure-morphology-property relationship is established. The stronger pi-pi interaction results in efficient electron hopping and balanced electron and hole mobilities attributed to good charge transport. Moreover, the reduced phase separation morphology of AQx-2-based bulk heterojunction blend boosts hole transfer and suppresses geminate recombination. Such success in molecule design and precise morphology optimization may lead to next-generation high-performance OSCs.
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| 3. |
- Bäckvall, Jan Erling, et al.
(författare)
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Author Spotlight
- 2021
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Ingår i: CCS CHEMISTRY. - : Chinese Chemical Society. - 2096-5745. ; 3:6, s. 1576-1579
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 4. |
- Liu, Feng, et al.
(författare)
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Modulating Structure Ordering via Side-Chain Engineering of Thieno[3,4-b]thiophene-Based Electron Acceptors for Efficient Organic Solar Cells with Reduced Energy Losses
- 2019
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 11:38, s. 35193-35200
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Tidskriftsartikel (refereegranskat)abstract
- Nonfullerene-based organic solar cells (OSCs) have made a huge breakthrough in the recent years. Introducing a proper side chain on the pi-conjugated backbone plays a vital role for further improving the power conversion efficiency (PCE) of OSCs due to easy tuning of the physical properties of the molecule such as absorption, energetic level, solid-state stacking, and charge transportation. More importantly, the side chain significantly affected the blend films morphology and thus determined the PCEs of the devices. In this work, two low-band-gap nonfullerene acceptors, ATT-4 and ATT-5, with an alkyl or branched alkyl substitute on indacenodithiophene (IDT) and thieno[3,4-b]thiophene (TbT) backbone were synthesized for investigating the effect of the substituent on the performance of the nonfullerene acceptors (NFAs). In comparison to ATT-1 with p-hexylphenyl-substituted IDT and n-octyl-substituted TbT moieties, ATT-4 and ATT-5 exhibit better crystallinity with shorter interchain distance and ordered molecular structure in neat and the corresponding blend films. The tailored ATT-5 exhibits a high PCE of 12.36% with a V-oc of 0.93 V, J(sc) of 18.86 mA cm(-2), and fill factor (FF) of 0.71, blending with a wide-band-gap polymer donor PBDB-T. Remarkably, although ATT-4 and ATT-5 exhibit broader light absorption, the devices obtained higher V-oc than that of ATT-1 mainly due to the reduced nonradiative recombination in the blend films. These results implied that side-chain engineering is an efficient approach to regulate the electronic structure and molecular packing of NFAs, which can well match with polymer donor, and obtain high PCEs of the OSCs with improved V-oc, J(sc), and FF, simultaneously.
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| 5. |
- Liu, Yanfeng, et al.
(författare)
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Electric Field Facilitating Hole Transfer in Non-Fullerene Organic Solar Cells with a Negative HOMO Offset
- 2020
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Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 124:28, s. 15132-15139
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Tidskriftsartikel (refereegranskat)abstract
- The record high photoinduced current and power conversion efficiencies of organic solar cells (OSCs) should be attributed to the significant contribution of non-fullerene electron acceptors via hole transfer to electron donors and/or a pronounced decrease in energy losses for exciton dissociation by aligned highest occupied molecular orbitals (HOMOs) or lowest unoccupied molecular orbitals (LUMOs). However, the hole transfer mechanism in those highly efficient non-fullerene OSCs with small HOMO offsets has not been extensively studied and fully understood, yet. Herein, we comparatively study the hole transfer kinetics in two OSCs with a positive (0.05 eV) and a negative (-0.07 eV) HOMO offset (Delta HOMO) based on polymer donor PTQ10 paired with non-fullerene acceptors ZITI-C or ZITI-N. Short-circuit current densities (J(sc)) of 20.42 and 12.81 mA cm(-2) are achieved in the OSCs based on PTQ10:ZITI-C (Delta HOMO = 0.05 eV) and PTQ10:ZITI-N (Delta HOMO = -0.07 eV) with an optimized donor (D):acceptor (A) ratio of 1:1, respectively, despite the small and even negative Delta HOMO. Results from time-resolved transient absorption spectroscopy show slower hole transfer (14.3 ps) in PTQ10:ZITI-N than that (3.7 ps) in PTQ10:ZITI-C. To understand the decent J(sc) value in the OSCs of PTQ10:ZITI-N, the temperature and electric field dependences of hole transfer are investigated in low-donor-content OSCs (D:A ratio of 1:9) in which photocurrent is dominated by the contribution via hole transfer from ZITI-N to PTQ10. Devices based on PTQ10:ZITI-C and PTQ10:ZITI-N show similar free charge generation behavior as a function of temperature, whereas the external quantum efficiencies of the PTQ10:ZITI-N device exhibit a much stronger bias dependence than that of PTQ10:ZITI-C, which suggests that the electric field facilitates exciton dissociation in PTQ10:ZITI-N where the energetic driving force alone cannot efficiently dissociate excitons.
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| 6. |
- Zhou, Zichun, et al.
(författare)
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High-efficiency small-molecule ternary solar cells with a hierarchical morphology enabled by synergizing fullerene and non-fullerene acceptors
- 2018
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Ingår i: NATURE ENERGY. - : NATURE PUBLISHING GROUP. - 2058-7546. ; 3:11, s. 952-959
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Tidskriftsartikel (refereegranskat)abstract
- Using combinatory photoactive blends is a promising approach to achieve high power conversion efficiency in ternary organic photovoltaics. However, the fundamental challenge of how to manipulate the morphology of multiple components and correlate structure details via device performance has not been well addressed. Achieving an ideal morphology that simultaneously enhances charge generation and transport and reduces voltage loss is an imperative avenue to improve device efficiency. Here, we achieve a high power conversion efficiency of 13.20 +/- 0.25% for ternary solar cells by using a combination of small molecules with both fullerene and non-fullerene acceptors, which form a hierarchical morphology consisting of a PCBM transporting highway and an intricate non-fullerene phase-separated pathway network. Carrier generation and transport find an optimized balance, and voltage loss is simultaneously reduced. Such a morphology fully utilizes the individual advantages of both fullerene and non-fullerene acceptors, demonstrating their indispensability in organic photovoltaics.
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