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Three-Phase Morphology Evolution in Sequentially Solution-Processed Polymer Photodetector: Toward Low Dark Current and High Photodetectivity
journal contribution
posted on 2018-01-17, 15:19 authored by Hanyu Wang, Shen Xing, Yifan Zheng, Jaemin Kong, Junsheng Yu, André D. TaylorSequentially solution-processed polymer
photodetectors (SSP PPDs) based on poly(3-hexylthiophene-2,5-diyl)
(P3HT)/[6,6]-phenyl C71-butyric acid methyl ester (PC71BM) are fabricated by depositing the top layers of PC71BM from an appropriate cosolvent of 2-chlorophenol (2-CP)/o-dichlorobenzene (ODCB) onto the predeposited bottom layers
of P3HT. By adjusting the ratio of 2-CP/ODCB in the top PC71BM layers, the resulting SSP PPD shows a decreased dark current and
an increased photocurrent, leading to a maximum detectivity of 1.23
× 1012 Jones at a wavelength of 550 nm. This value
is 5.3-fold higher than that of the conventional bulk heterojunction
PPD. Morphology studies reveal that the PC71BM partially
penetrates the predeposited P3HT layer during the spin-coating process,
resulting in an optimal three-phase morphology with one well-mixed
interdiffusion P3HT/PC71BM phase in the middle of the bulk
and two pure phases of P3HT and PC71BM at the two electrode
sides. We show that the pure phases form high Schottky barriers (>2.0
eV) at the active layer/electrodes interface and efficiently block
unfavorable reverse charge carrier injection by significantly decreasing
the dark current. The interdiffussion phase enlarges the donor–acceptor
interfacial area leading to a large photocurrent. We also reveal that
the improved performance of SSP PPDs is also due to the enhanced optical
absorption, improved P3HT crystallinity, increased charge carrier
mobilities, and suppressed bimolecular recombination.
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predeposited bottom layerswell-mixed interdiffusion P 3HT 71 BM phaseHigh Photodetectivity Sequentially solution-processed polymer photodetectorscharge carrier mobilitiescharge carrier injectionbulk heterojunction PPDpredeposited P 3HT layerPC 71 BMP 3HT crystallinityThree-Phase Morphology EvolutionCPSSP PPDsP 3HT C 71butyric acid methyl esterSequentially Solution-Processed Polymer PhotodetectorPC 71 BM layersP 3HTODCB
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