Spectroscopic Ellipsometry of FAxMA1−xPbI3 Solid Solution Hybrid Perovskite Single Crystals
Maria Isabel Alonso a, Bethan Charles b, Adrián Francisco-Lopez a, Miquel Garriga a, Mariano Campoy-Quiles a, Mark Weller b, Alejandro Goñi a c
a Institut de Ciència de Materials de Barcelona (ICMAB-CSIC, Campus UAB, Bellaterra, Spain
b Dept. of Chemistry & Centre for Sustainable Chemical Technologies, University of Bath, UK, Claverton Down, Bath BA2 7AY, Reino Unido, United Kingdom
c Institució Catalana de Recerca i Estudis Avançats (ICREA), Spain, Passeig Lluis Companys 23, Barcelona, Spain
Poster, Maria Isabel Alonso, 048
Publication date: 23rd April 2020

Organic-inorganic perovskites base on the generic formula ABX3 , where X denotes a halide anion and A and B stand for an organic and a metal cation, respectively. These hybrid compounds are semiconductors with highly interesting and tunable properties and are subject of intense research for several applications, mainly in solar cells but also as LEDs or lasers. For all these applications, knowledge of the optical properties is both of fundamental and practical interest. For example, detailed knowledge of the optical constants enables better designs for optimisation of the harvesting and out coupling of light in the mentioned devices. Tunability of the optical properties may be accomplished by site-substituted solid solutions in A, B, or X sites. In particular, some mixed-cation systems show increased stability for applications.

In this work, we report on the variation of the optical constants in mixed A-site cation methylammonium (MA)/formamidinium (FA) lead iodide hybrid FAxMA1−xPbI3 as measured and analysed by spectroscopic ellipsometry in single crystal samples at room temperature. The detailed structural phase behaviour of the samples is well established [1]. The main result in this work is the analysis of the observed electronic transitions as a function of the composition obtained from fitting the numerically built second derivatives of the dielectric function[2]. The results are discussed together with other optical measurements (f.i., photoluminescence) by relative comparison to the electronic structures of the parent compounds [3].

The Spanish Ministerio de Ciencia, Innovación y Universidades is acknowledged for its support through Grant No. SEV-2015-0496 in the framework of the Spanish Severo Ochoa Centre of Excellence program and through Grants MAT2015-70850-P (HIBRI2) and PGC2018-095411-B-100 (RAINBOW). We also thank the AGAUR for grant 2017-SGR-00488. BC thanks the EPSRC for PhD studentship funding via the CSCT CDT (EP/G03768X/1, EP/L016354/1). AFL acknowledges the PhD programme in Materials Science from Universitat Autònoma de Barcelona and a FPI fellowship (BES-2016-076913) from the Spanish Ministerio, co-financed by the European Social Fund.

© Fundació Scito
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