半導體奈米晶體之間能量傳遞的理論研究

Abstract

太陽能電池為能源永續發展的重要技術，然而其轉換效率普遍無法達到預期，所以許多改善太陽能電池能源轉換效率的方法接踵而生。例如，利用半導體量子點大小進而能夠吸收特定波段光子等特性，增加太陽能電池的光吸收波段，形成Luminescence down-shifting (LDS)，進而提升能量轉換效率。而在量子點吸收來自太陽光的能量之後，因其三維侷限性的關係使得量子點內的激子被限制在其中。然而我們發現，激子可藉由偶極－偶極交互作用傳遞到另一個量子點內，形成福斯特能量傳遞(Förster resonance energy transfer)。 本篇論文利用波包近似法(Envelope function approximation)計算耦合量子點之間不同電子與空軌域自旋數之激子之間的偶極－偶極交互作用並與k．p theory之參數做連結。接著，由薛丁格方程式出發，建立Quantum master equation的理論方法，並以此為基礎來分析耦合量子點之間其之間能量傳遞的動態行為。

Solar cell plays an important role in energy conservation. However its energy conversion efficiency is not as satisfactory as expected. One of the methods to improve the efficiency is to use the semiconductor quantum dots (QDs), which can be controlled by their sizes to fit the requirement for absorbing photon with specific wavelength, to improve the poor response of solar cell in lower wavelength region and then enhance the solar cell efficiency. The excitons are confined because of the 3D confinement of QDs. However we found that the excitons can transfer the excitation energy by the dipole-dipole interaction instead of being trapped in QDs. In this thesis, we use the envelope function approximation to calculate the dipole-dipole interaction between the exciton in QDs with different spin quantum numbers of electron and hole and connect to the k．p theory parameters. Next , start from Schrödinger equation, we establish the quantum master equation approach, using it to study on the dynamic analysis between the coupled QDs.