| 1. |
- Han, Jianhua, et al.
(författare)
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In situ formation of thermoset matrices for improved stability in organic photovoltaics
- 2024
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Ingår i: Joule. - 2542-4351. ; In Press
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Tidskriftsartikel (refereegranskat)abstract
- The performance of organic photovoltaics (OPVs) has rapidly increased. Yet, achieving long-term stability in the nano-morphology and thereby sustaining device performance remains challenging. Herein, we show that incorporating in-situ-forming cross-linked thermoset (CLT) matrices into the bulk heterojunction blends is a simple, general, and efficient strategy for high-performing and resilient OPVs. Our simulations and experimental data prove that these high-modulus CLT matrices featuring hydrogen-bonding interactions can freeze the nano-morphology, resulting in long-term thermal and photostable OPV devices. We demonstrate that this approach works efficiently with eight different blends and show that OPV devices can withstand 85°C for 1,000 h without losing performance. Blends with CLT matrices double the energy generated from OPV devices, showing an energy density output of 4,054 mW⋅h cm−2 over an 11-week operating period under outdoor conditions. This methodology opens avenues for both developing new thermoset networks for OPV and their use in other optoelectronic applications.
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| 2. |
- Liu, Jian, et al.
(författare)
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Amphipathic Side Chain of a Conjugated Polymer Optimizes Dopant Location toward Efficient N-Type Organic Thermoelectrics
- 2021
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Ingår i: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095. ; 33
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Tidskriftsartikel (refereegranskat)abstract
- There is no molecular strategy for selectively increasing the Seebeck coefficient without reducing the electrical conductivity for organic thermoelectrics. Here, it is reported that the use of amphipathic side chains in an n-type donor-acceptor copolymer can selectively increase the Seebeck coefficient and thus increase the power factor by a factor of approximate to 5. The amphipathic side chain contains an alkyl chain segment as a spacer between the polymer backbone and an ethylene glycol type chain segment. The use of this alkyl spacer does not only reduce the energetic disorder in the conjugated polymer film but can also properly control the dopant sites away from the backbone, which minimizes the adverse influence of counterions. As confirmed by kinetic Monte Carlo simulations with the host-dopant distance as the only variable, a reduced Coulombic interaction resulting from a larger host-dopant distance contributes to a higher Seebeck coefficient for a given electrical conductivity. Finally, an optimized power factor of 18 mu W m(-1) K-2 is achieved in the doped polymer film. This work provides a facile molecular strategy for selectively improving the Seebeck coefficient and opens up a new route for optimizing the dopant location toward realizing better n-type polymeric thermoelectrics.
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| 3. |
- Paleti, Sri Harish Kumar, et al.
(författare)
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Hexanary blends : a strategy towards thermally stable organic photovoltaics
- 2023
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Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Non-fullerene based organic solar cells display a high initial power conversion efficiency but continue to suffer from poor thermal stability, especially in case of devices with thick active layers. Mixing of five structurally similar acceptors with similar electron affinities, and blending with a donor polymer is explored, yielding devices with a power conversion efficiency of up to 17.6%. The hexanary device performance is unaffected by thermal annealing of the bulk-heterojunction active layer for at least 23 days at 130 °C in the dark and an inert atmosphere. Moreover, hexanary blends offer a high degree of thermal stability for an active layer thickness of up to 390 nm, which is advantageous for high-throughput processing of organic solar cells. Here, a generic strategy based on multi-component acceptor mixtures is presented that permits to considerably improve the thermal stability of non-fullerene based devices and thus paves the way for large-area organic solar cells.
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| 4. |
- Xu, Han, et al.
(författare)
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Dissecting the structure-stability relationship of Y-series electron acceptors for real-world solar cell applications
- 2023
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Ingår i: Joule. - 2542-4351. ; 7:9, s. 2135-2151
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Tidskriftsartikel (refereegranskat)abstract
- Despite striking progress toward improving the photovoltaic (PV) performance of organic solar cells (OSCs) with recent Y-series non-fullerene acceptors (Y-NFAs), knowledge about their outdoor performance under real-world conditions and photodegradation mechanisms remains elusive, which is urgently needed to close the lab-to-fab gap of OSCs. Herein, for the first time, we study the structure-outdoor-stability relationship of Y-NFAs. We show that Y-NFAs with long internal side-chains exhibit high energy barriers for photoisomerization, and fluorinated end-groups can enhance the structural confinement to inhibit the photodegradation pathway and thereby improve device stability. Furthermore, the performance loss of Y-NFA-based OSCs under illumination is mainly driven by increased trap-assisted recombination over time. The structure-stability correlation and demonstration of outdoor performance of these state-of-the-art Y-NFA cells provided in this study highlight molecular engineering of device stability control to minimize power output losses in real-world climates.
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