Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV16)
Publication date: 28th March 2016
The compound class of hybrid perovskites regained great attention since the discovery of the superior electronic and optical properties of methylammonium lead iodide (MAPI) and with it, its application in photovoltaics. Hybrid-perovskite based solar cells have reached record efficiencies of over 20 % to this day, which are comparable to commercial silicon solar cells. In order to bring hybrid perovskite based solar cells to the market, solutions for MAPI's intrinsic sensitivity toward humidity have to be found. [1,2]
Looking at structure-property relations dimensionality is an important feature to tailor the material’s characteristics. Two-dimensional compounds derived from MAPI such as (PEA)2(MA)2[Pb3I10] (PEA = phenylethylammonium, MA = methylammonium) showed higher moisture resistance and ready availability of high-quality films while still displaying reasonable efficiencies (η = 4.73 %) [3]. Another option to tailor the material’s properties is the choice of the organic cation. Theoretical studies by Frost et al. indicated that efficiencies can be improved even further by increasing the internal electric field generated by the polar organic cation which leads to better charge separation and improved carrier lifetimes. The parameter we can influence directly is the organic cation’s polarity as well as hydrophobicity when replacing hydrogen by the more electronegative fluorine. [4]
Both concepts have been considered when synthesizing the compound (FC2H4NH3)2PbCl4, which was characterized by DSC, PXRD, 1H, 13C and 207Pb solid-state NMR spectroscopy, absorption spectroscopy and time-resolved photoluminescence measurements.
References:
[1] M. K. Nazeeruddin, H. Snaith, MRS Bull. 2015,40, 641.
[2] National Center for Photovoltaics, Best Research-Cell Efficiencies ; http://www.nrel.gov/ncpv/images/efficiency_chart.jpg.
[3] I. C. Smith, E. T. Hoke, D. Solis-Ibarra, M. D. McGehee, H. I. Karunadasa, Angew. Chem. 2014, 126, 11414.
[4] J. M. Frost, K. T. Butler, F. Brivio, C. H. Hendon, M. van Schilfgaarde, A. Walsh, Nano Lett. 2014, 14, 2584.