TY - JOUR
T1 - Origin of Pronounced Nonlinear Band Gap Behavior in Lead-Tin Hybrid Perovskite Alloys
AU - Goyal, Anuj
AU - McKechnie, Scott
AU - Pashov, Dimitar
AU - Tumas, William
AU - Schilfgaarde, Mark Van
AU - Stevanović, Vladan
PY - 2018/6/12
Y1 - 2018/6/12
N2 - Mixed lead-tin hybrid perovskite alloy CH3NH3(Pb1-xSnx)I3 attracted significant attention lately because of the reduction of its band gap below both end compounds, which makes it a promising bottom cell material in all-perovskite tandem solar cells. The effect is a consequence of a strongly nonlinear dependence of the alloy band gap on chemical composition. Here, we use electronic structure calculations at different levels of theory (density functional theory (DFT), hybrid DFT, and QSGW, with and without spin-orbit interactions) to investigate the presently elusive origin of this effect. Contrary to current conflicting studies, our results show that neither spin-orbit interactions nor the composition induced changes of the crystal structure and ordering of atoms contributes to the nonlinearity of the band gap. We find that the strong nonlinearity is primarily a consequence of chemical effects, i.e., the mismatch in energy between s and p atomic orbitals of Pb and Sn, which form the band edges of the alloy. These results unravel the nature of the band gap bowing in Sn/Pb hybrid perovskite alloys and offer a relatively simple way to estimate evolution of the band gap in other hybrid perovskite alloys. ©
AB - Mixed lead-tin hybrid perovskite alloy CH3NH3(Pb1-xSnx)I3 attracted significant attention lately because of the reduction of its band gap below both end compounds, which makes it a promising bottom cell material in all-perovskite tandem solar cells. The effect is a consequence of a strongly nonlinear dependence of the alloy band gap on chemical composition. Here, we use electronic structure calculations at different levels of theory (density functional theory (DFT), hybrid DFT, and QSGW, with and without spin-orbit interactions) to investigate the presently elusive origin of this effect. Contrary to current conflicting studies, our results show that neither spin-orbit interactions nor the composition induced changes of the crystal structure and ordering of atoms contributes to the nonlinearity of the band gap. We find that the strong nonlinearity is primarily a consequence of chemical effects, i.e., the mismatch in energy between s and p atomic orbitals of Pb and Sn, which form the band edges of the alloy. These results unravel the nature of the band gap bowing in Sn/Pb hybrid perovskite alloys and offer a relatively simple way to estimate evolution of the band gap in other hybrid perovskite alloys. ©
UR - http://www.scopus.com/inward/record.url?scp=85046690722&partnerID=8YFLogxK
U2 - 10.1021/acs.chemmater.8b01695
DO - 10.1021/acs.chemmater.8b01695
M3 - Article
AN - SCOPUS:85046690722
SN - 0897-4756
VL - 30
SP - 3920
EP - 3928
JO - CHEMISTRY OF MATERIALS
JF - CHEMISTRY OF MATERIALS
IS - 11
ER -
