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High Performance and Low-Cost Hole Transporting Layer for Efficient and Stable Perovskite Solar Cells

Abstract

Here we report, small molecule oxidant 2,3,5,6-Tetrafluoro-7,7,8,8,-tetracyano-quinodimethane (F4TCNQ) doped, low cost 2',7'-bis(bis(4-methoxyphenyl)amino)spiro[cyclopenta[2,1-b:3,4-b']dithiophene-4,9'-fluorene] (FDT) hole transport layer (HTL) for efficient mixed organic cation based MA0.6FA0.4PbI3 (MA=methyl ammonium, FA=formamidinium) perovskite solar cells (PSC); fabricated via highly reproducible controlled nucleation assisted restricted volume solvent annealing method, having full temperature compatibility with flexible substrates. The optimized (1 wt%) F4TCNQ doped FDT HTL based devices (F-FDT devices) demonstrate simultaneous enhancement in photovoltaic performance and device stability as well as significant reduction in photo-current hysteresis, as compared to conventional Bis(trifluoromethylsulfonyl)amine lithium (Li-TFSI) additive based FDT HTL devices (L-FDT devices). Adding to the merits, F-FDT PSCs exhibit about 75% higher device stability compared to conventional L-FDT devices during the course of three weeks. Mott-Schottky analysis and in-depth charge transport characterization was carried out using electrochemical impedance spectroscopy (EIS) of the fabricated devices to understand the superior performance of the F-FDT devices. In addition, a detailed polaronic intensity characterization of the doped HTL films was performed via ultraviolet-visible near-infrared (UV-vis-NIR) spectroscopy to investigate the underlying mechanism. Mitigated photocurrent hysteresis in F-FDT device have also been examined in terms of the inherent electrode polarization phenomenon. Furthermore, the superior device stability of the F-FDT PSCs has been probed in terms of variation in electronic properties, surface wettability, crystallinity, microstrain dislocation density and a detailed picture of the underlying mechanism behind stability enhancement is presented.

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Publication details

The article was received on 26 May 2017, accepted on 10 Jul 2017 and first published on 12 Jul 2017


Article type: Paper
DOI: 10.1039/C7CP03551A
Citation: Phys. Chem. Chem. Phys., 2017, Accepted Manuscript
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    High Performance and Low-Cost Hole Transporting Layer for Efficient and Stable Perovskite Solar Cells

    M. A. Mahmud, N. K. Elumalai, M. B. Upama, D. Wang, V. R. Gonçales, M. Wright, C. Xu, F. Haque and A. Uddin, Phys. Chem. Chem. Phys., 2017, Accepted Manuscript , DOI: 10.1039/C7CP03551A

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