TY - JOUR
T1 - Frenkel Excitons in Vacancy-Ordered Titanium Halide Perovskites (Cs2TiX6)
AU - Kavanagh, Seán R.
AU - Savory, Christopher N.
AU - Liga, Shanti M.
AU - Konstantatos, Gerasimos
AU - Walsh, Aron
AU - Scanlon, David O.
N1 - Publisher Copyright:
© 2022 The Authors. Published by American Chemical Society.
PY - 2022/12/1
Y1 - 2022/12/1
N2 - Low-cost, nontoxic, and earth-abundant photovoltaic materials are long-sought targets in the solar cell research community. Perovskite-inspired materials have emerged as promising candidates for this goal, with researchers employing materials design strategies including structural, dimensional, and compositional transformations to avoid the use of rare and toxic elemental constituents, while attempting to maintain high optoelectronic performance. These strategies have recently been invoked to propose Ti-based vacancy-ordered halide perovskites (A2TiX6; A = CH3NH3, Cs, Rb, or K; X = I, Br, or Cl) for photovoltaic operation, following the initial promise of Cs2SnX6 compounds. Theoretical investigations of these materials, however, consistently overestimate their band gaps, a fundamental property for photovoltaic applications. Here, we reveal strong excitonic effects as the origin of this discrepancy between theory and experiment, a consequence of both low structural dimensionality and band localization. These findings have vital implications for the optoelectronic application of these compounds while also highlighting the importance of frontier-orbital character for chemical substitution in materials design strategies.
AB - Low-cost, nontoxic, and earth-abundant photovoltaic materials are long-sought targets in the solar cell research community. Perovskite-inspired materials have emerged as promising candidates for this goal, with researchers employing materials design strategies including structural, dimensional, and compositional transformations to avoid the use of rare and toxic elemental constituents, while attempting to maintain high optoelectronic performance. These strategies have recently been invoked to propose Ti-based vacancy-ordered halide perovskites (A2TiX6; A = CH3NH3, Cs, Rb, or K; X = I, Br, or Cl) for photovoltaic operation, following the initial promise of Cs2SnX6 compounds. Theoretical investigations of these materials, however, consistently overestimate their band gaps, a fundamental property for photovoltaic applications. Here, we reveal strong excitonic effects as the origin of this discrepancy between theory and experiment, a consequence of both low structural dimensionality and band localization. These findings have vital implications for the optoelectronic application of these compounds while also highlighting the importance of frontier-orbital character for chemical substitution in materials design strategies.
UR - http://www.scopus.com/inward/record.url?scp=85142649661&partnerID=8YFLogxK
U2 - 10.1021/acs.jpclett.2c02436
DO - 10.1021/acs.jpclett.2c02436
M3 - Article
C2 - 36414263
AN - SCOPUS:85142649661
SN - 1948-7185
VL - 13
SP - 10965
EP - 10975
JO - Journal of Physical Chemistry Letters
JF - Journal of Physical Chemistry Letters
IS - 47
ER -