Bandgap tuning with thermal residual stresses induced in a quantum dot.
Lattice distortion induced by residual stresses can alter electronic and mechanical properties of materials significantly. Herein, a novel way of the bandgap tuning in a quantum dot (QD) by lattice distortion is presented using 4-nm-sized CdS QDs grown on a TiO2 particle as an application example. The bandgap tuning (from 2.74 eV to 2.49 eV) of a CdS QD is achieved by suitably adjusting the degree of lattice distortion in a QD via the tensile residual stresses which arise from the difference in thermal expansion coefficients between CdS and TiO2. The idea of bandgap tuning is then applied to QD-sensitized solar cells, achieving ≈60% increase in the power conversion efficiency by controlling the degree of thermal residual stress. Since the present methodology is not limited to a specific QD system, it will potentially pave a way to unexplored quantum effects in various QD-based applications.
Department of Materials Science and Engineering and Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), Pohang, 790-784, Republic of Korea.
Eui-Hyun
EH
Kong
Soo-Hyun
SH
Joo
Hyun-Jin
HJ
Park
Seungwoo
S
Song
Yong-June
YJ
Chang
Hyoung Seop
HS
Kim
Hyun Myung
HM
Jang
bandgap tuning; lattice distortion; photovoltaics; quantum dots; residual stress