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.com
Volume 7
Innovative Energy & Research
ISSN: 2576-1463
Advanced Energy Materials 2018
August 13-14, 2018
August 13-14, 2018 | Dublin, Ireland
20
th
International Conference on
Advanced Energy Materials and Research
Innov Ener Res 2018, Volume 7
DOI: 10.4172/2576-1463-C1-003
Elucidating the role of Sn-substitution and Pb-Vc in regulating stability and carrier concentration in
CH3NH3Pb1−X−YSnXVcYI3
Saswata Bhattacharya
Indian Institute of Technology Delhi, India
I
norganic-organic perovskites, CH
3
NH
3
PbI
3
in particular, have recently drawn significant attention in improving solar cell’s
performance due to their long diffusion length, high carrier mobility, suitable optical band gaps, and strong absorption
of light. However, the presence of Pb has rendered its usage in developing non-toxic lead-free devices. Therefore, reducing
the extent of Pb by substituting a suitable alternative metal (e.g. Sn, Ge, Sr, etc.) in the perovskite has become extremely
important. Moreover, inclusion of Sn in the perovskite network (i.e. CH
3
NH
3
Pb1−xSn
x
I
3
) can reduce the optical band gap.
This enables the perovskite to absorb all visible lights of the solar spectrum along with some ultraviolet to near-infrared
photons (up to 1.1 eV). Therefore, digging deep into the atomistic insights and electronic structure of Sn based perovskites has
become profoundly important for designing efficient energy harvesting materials. In this talk, I shall address the role of Sn-
substitution and Pb-vacancy (Vc) in regulating stability and carrier concentration of CH
3
NH
3
Pb1−X−YSn
X
V
cY
I
3
using state-of-
the-art density functional theory (DFT). The finite temperature effect is duly included in our theoretical calculations involving
lattice thermal vibration at a given temperature. We find that at low temperature the system prefers Pb-Vc and the most stable
configuration does not prefer any Pb at 50% Sn concentration. However, the Pb-Vcs become unfavourable above 250K due
to the reduced linearity of I-Sn-I bonds. For n-type host the Sn substitution is more preferable than Pb-Vc formation, while
for p-type host the trend is exactly opposite. The charge states of both substituted Sn and Pb-Vc are found to be dependent
on the Sn concentration, which in turn alters the perovskite’s property from n-type to p-type beyond 50% Sn substitution. All
our theoretical explanations, that were hitherto unknown, are perfectly in agreement with previously available experimental-
observations.
saswata@physics.iitd.ac.in