We investigated the structural stability, density of
states (DOS),
optical and electronic properties of Cs2TeX6 (X = Cl, Br, I) vacancy-ordered double perovskites (VoDPs) using
first-principles calculations. These VoDPs exhibit good structural
stability based on tolerance factors, the Brown equation, and the
formation energy. The calculated indirect bandgaps of Cs2TeX6 systems are also in agreement with the reported experimental
values. We observed that the eigenband corresponding to the minima
of the conduction band (CB) seems to be detached from the CB upon
the consideration of spin–orbit coupling (SOC), and more band
bending occurs at the “L” point. Overall, the high absorption
coefficient (≈105 cm–1) of the
Cs2TeI6 system, together with other optoelectronic
properties in the visible spectrum range with moderate reflectance
(∼33%), makes it a suitable photovoltaic (PV) absorber material.
Furthermore, the PV performance of Cs2TeI6 material-based
single-junction solar cell (SC) is investigated in the planar regular
device configuration (n–i–p structure) for two different
electron transport materials (ETMs: TiO2 and WS2). The optimum power conversion efficiency (PCE) of the FTO/n-WS2/Cs2TeI6/p-NiO SC configuration is found
to be ∼23.74% together with open-circuit voltage (V
oc), current density (J
sc),
and fill factor (FF) values of ∼1.094 V, 26.955 mA/cm2, and 80.53%, respectively. In addition, the photovoltaic response
of the Cs2TeX6 absorber-based SC is also substantiated
using the spectroscopic limited maximum efficiency (SLME) approach.
Thus, the present work will play an important role in the realization
of efficient lead-free VoDP-based single-junction SCs and other optoelectronic
applications.