Band structure engineering of quantum dot applied devices and performance improvement

Abstract

Quantum dot is 0 dimensional materials that the size of the material is under few nanometers. Through confining the size of the material, quantum confinement effect can manipulate the intrinsic properties of the material. Especially, quantization of electronic band structure of the quantum dot enabled to control light absorption spectrum and light emitting wavelength, making quantum dot one of the most promising materials for photo-electronic applications such as display and solar cell. However, low understanding and underdeveloped research progress of quantum dot applied devices failed highly efficient device fabrication. In this research, band engineering of the devices of solar cell and surface enhanced Raman scattering substrates are mostly developed for the performance improvement. In quantum dot solar cell, due to the lower hole mobility and extracting distance of carriers in band structure, the hole-extraction is mainly considered as the performance limitation. To improve hole extraction, bilayered structure of hole transport materials are applied. One is large band-gap materials to block the leakage current and the other layer for relaxing interfacial dipole to optimize band structure. Through combination of bi-layered hole transport materials, the optimized band structure is obtained. In newly designed hole transport material, the device performance is enhanced by 47% compare to conventional $MoO_3$ hole transport material. In Surface-enhanced Raman scattering (SERS) research, to maximize localized surface plasmonic resonance of the plasmonic structure, the additional photocurrent is injected to plasmonic structure by utilizing quantum dot photovoltaic substrate. Quantum dot substrate generate carrier from incident Raman laser beam, and photo-carriers are induced to transfer to gold nano-structure. The Raman signal is enhanced by 50 % to 250 % depending on detecting materials.