P4917 Solar cells materials by design: Hybrid pyroxene corner-sharing VO4 tetrahedral chains

Fedwa El-Mellouhia, Akinlolu Akandeb, Carlo Mottac, Sergey Rashkeeva, Golibjon Berdiyorova, Mohamed El-Amine Madjeta, Asma Marzouka, El-Tayeb Bentriaa, Stefano Sanvitoc, Sabre Kaisa, d, e, Fahhad H Alharbia, d

a, Qatar Environment and Energy Research Institute, Hamad Bin Khalifa University, Doha, P.O. Box: 34110, Doha, 0, QA
b, Department of Life Sciences, Institute of Technology, Ash Lane, Sligo, , Ireland
c, School of Physics, AMBER and CRANN Institute, Trinity College, Dublin 2, , Ireland
d, College of Science and Engineering, Hamad Bin Khalifa University, Doha, , QA
e, Purdue University, West Lafayette, Indiana 47907, , USA

Hybrid organic-inorganic frameworks provide numerous combinations of materials with a wide range of structural and electronic properties, which enable their use in various applications. In recent years, some of these hybrid materials (especially lead-based halide perovskites) have been successfully used for the development of highly efficient solar cells. The large variety of possible hybrid materials inspired us into the search of other organic-inorganic frameworks, which may exhibit enhanced performance when compared to conventional lead-halide perovskites. In this work we design a new class of low-dimensional hybrid oxides for photovoltaic applications by using electronic structure calculations in combination with analysis from existing materials databases. We focus on oxide vanadium pyroxenes (tetrahedron-based frameworks), mainly due to their high stability and non-toxicity. Also, vanadium can change its oxidation state from 5+ to 2+ enabling a variety of morphologies and structural network manipulations and offering a large spectrum of inorganic and hybrid stable structures that could be synthesized. We report a detailed first-principles computational study of the structural, electronic, optical and transport properties of low-dimensional hybrid vanadate pyroxene corner-sharing VO4 tetrahedral chains oxide materials with the general formula [A]VO3 where [A] are molecular cations (A = NH4+, PH4+, H3O+, H3S+, CH3NH3+, CH(NH2)2+, and CH3CH2NH3+). We assessed the potential of this family of compounds for photovoltaic applications. It was demonstrated (by one to one comparison between CsVO3 and NH4VO3) that hybrid vanadates are as good as their inorganic counterparts in terms of transport properties.In order to overcome the shortcoming of large electronic bandgaps in this family of compounds (with values outside the optimal 1.0-1.7 eV range) we computationally searched for new hybrid vanadates with little or no experimental information. Crucially, we have shown that cation substitution can significantly change the structure. The bandgap may be tuned either by inducing crystal field splitting due to the deformation of the VO4 tetrahedral network or by molecular deprotonation with subsequent formation of strong O-H—S hydrogen bond with the molecular cation. While both mechanisms are correlated, the latter yields a more sizable reduction in the bandgap with beneficial implication on the optical absorption properties in the visible range of the solar spectrum. We identified H3SVO3 as a strong absorber with a reasonable bandgap that is stable against phase separation and moisture. This compound could attract further experimental investigation and additional computational work is underway.