Bandgap Tuning with Thermal Residual Stresses Induced in a Quantum Dot

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2014-09, Vol.10 (18), p.3678-3684
• Main Authors: Kong, Eui-Hyun, Joo, Soo-Hyun, Park, Hyun-Jin, Song, Seungwoo, Chang, Yong-June, Kim, Hyoung Seop, Jang, Hyun Myung
• Format: Article
• Language: English
• Subjects: Adjustment; bandgap tuning; Distortion; Energy conversion efficiency; lattice distortion; Lattices; Nanotechnology; photovoltaics; Quantum dots; Residual stress; Semiconductors; Tensile stress; Titanium dioxide; Tuning
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.201400392

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. Quantum dots with thermal residual stresses: A novel way of bandgap tuning in a quantum dot (QD) by lattice distortion using 4‐nm‐sized CdS QDs grown on a TiO2 particle. 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 stresses.