Elucidating the factors limiting the photovoltaic performance of mixed Sb-Bi halide elpasolite absorbers
Author(s)
Type
Journal Article
Abstract
Although Cs2AgBiBr6 halide elpasolites have gained substantial attention as potential nontoxic and stable alternatives to lead-halide perovskites, they are limited by their wide bandgaps >2.2 eV. Alloying with Sb into the pnictogen site has been shown to be an effective method to lower the bandgap, but this has not translated into improvements in photovoltaic (PV) performance. In this work, the underlying causes are investigated. Pinhole-free films of Cs2Ag(SbxBi1-x)Br6 are achieved through antisolvent dripping, but PV devices still exhibit a reduction in power conversion efficiency (PCE) from 0.44±0.02% (without Sb) to 0.073±0.007% (90% Sb; lowest bandgap). There is a 0.7 V reduction in the open-circuit voltage, which correlates with the appearance of a sub-bandgap state approximately 0.7 eV below the optical bandgap in the Sb-containing elpasolite films, as found in both absorbance and photoluminescence measurements. Through detailed Williamson-Hall analysis, it is found that adding Sb into the elpasolite films leads to an increase in film strain. This strain is relieved through aerosol-assisted solvent treatment, which reduces both the sub-bandgap state density and energetic disorder in the films, as well as reducing the fast early decay in the photogenerated carrier population due to trap filling. This work shows that Sb alloying leads to the introduction of extra sub-bandgap states that limit the PV performance, but can be mitigated through post-annealing treatment to reduce disorder and strain.
Date Issued
2022-11
Date Acceptance
2022-09-08
Citation
Solar RRL, 2022, 6 (11), pp.1-9
ISSN
2367-198X
Publisher
Wiley
Start Page
1
End Page
9
Journal / Book Title
Solar RRL
Volume
6
Issue
11
Copyright Statement
© 2022 The Authors. Solar RRL published by Wiley-VCH GmbH
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
License URL
Sponsor
Downing College, Cambridge
Royal Academy of Engineering
Royal Academy Of Engineering
Engineering & Physical Science Research Council (EPSRC)
Identifier
https://onlinelibrary.wiley.com/doi/10.1002/solr.202200749
Grant Number
RF\201718\17101
RF\201718\17101
EP/V014498/1
Subjects
Science & Technology
Technology
Energy & Fuels
Materials Science, Multidisciplinary
Materials Science
double perovskites
elpasolite
photovoltaics
post-treatment annealing
thin films
trap states
DOUBLE-PEROVSKITE
BISMUTH
SEMICONDUCTORS
FILMS
Publication Status
Published
Date Publish Online
2022-09-20