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- Wilken, Sebastian, et al.
(författare)
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How to Reduce Charge Recombination in Organic Solar Cells: There are Still Lessons to Learn from P3HT:PCBM
- 2021
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Ingår i: Advanced Electronic Materials. - : Wiley. - 2199-160X .- 2199-160X. ; 7:5
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Tidskriftsartikel (refereegranskat)abstract
- Suppressing charge recombination is key for organic solar cells to become commercial reality. However, there is still no conclusive picture of how recombination losses are influenced by the complex nanoscale morphology. Here, new insight is provided by revisiting the P3HT:PCBM blend, which is still one of the best performers regarding reduced recombination. By changing small details in the annealing procedure, two model morphologies are prepared that vary in phase separation, molecular order, and phase purity, as revealed by electron tomography and optical spectroscopy. Both systems behave very similarly with respect to charge generation and transport, but differ significantly in bimolecular recombination. Only the system containing P3HT aggregates of high crystalline quality and purity is found to achieve exceptionally low recombination rates. The high-quality aggregates support charge delocalization, which assists the re-dissociation of interfacial charge-transfer states formed upon the encounter of free carriers. For devices with the optimized morphology, an exceptional long hole diffusion length is found, which allows them to work as Shockley-type solar cells even in thick junctions of 300 nm. In contrast, the encounter rate and the size of the phase-separated domains appear to be less important.
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| 2. |
- Yu, Liyang, 1986, et al.
(författare)
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Sequential doping of solid chunks of a conjugated polymer for body-heat-powered thermoelectric modules
- 2021
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 119:18
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Tidskriftsartikel (refereegranskat)abstract
- Sequential doping of 1 mm3 sized cubes of regio-regular poly(3-hexylthiophene) (P3HT) with 2,3,5,6-tetrafluoro-tetracyanoquinodimethane is found to result in a doping gradient. The dopant ingresses into the solid material and after two weeks of sequential doping yields a 250 μm thick doped surface layer, while the interior of the cubes remains undoped. The doping gradient is mapped with energy dispersive x-ray spectroscopy (EDX), which is used to estimate a diffusion coefficient of 1 × 10-10 cm2 s-1 at room temperature. The cubes, prepared by pressing at 150 °C, feature alignment of polymer chains along the flow direction, which yields an electrical conductivity of 2.2 S cm-1 in the same direction. A 4-leg thermoelectric module was fabricated with slabs of pressed and doped P3HT, which generated a power of 0.22 μW for a temperature gradient of 10.2 °C generated by body heat.
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