FABRICATION AND OPTIMIZATION OF LIGHT CARRIER COLLECTION MANAGEMENT STRUCTURE USING LEAD SULFIDE QUANTUM DOTS AS LIGHT ABSORBER

Open Access
Author:
Nguyen, Nghia Dai
Graduate Program:
Engineering Science and Mechanics
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
October 15, 2014
Committee Members:
  • Stephen Joseph Fonash, Dissertation Advisor
  • Wook Jun Nam, Committee Chair
  • Osama O Awadelkarim, Committee Member
  • Jeffrey Brownson, Special Member
Keywords:
  • PbS
  • quantum dots
  • light absorber
  • photovoltaic
  • solar cell
Abstract:
Light and carrier collection management (LCCM) architecture for thin film photovoltaic and detector is among the latest attempts to enhance light absorption while maintaining the collection of charge carriers. Exciting progress has already been made with amorphous Si (a-Si) solar cells where short circuit current (Jsc) is greatly enhanced while no other sacrifice is made for other performances. Effective light trapping phenomena inside the structure are considered the main contributors. This work explores and studies the known phenomena such as radiation, traveling waveguided, traveling Bloch, Mie, and plasmonic modes. Lead sulfide (PbS) colloidal quantum dots (CQDs) is a novel light absorber that is categorized in the third generation of solar cells where it shows potential to be highly efficient (more than Shockley-Queisser efficiency limit) yet still very affordable to made. They exhibit quantum mechanical properties that may improve the photovoltage and photocurrent beyond their classical limits. However, its use mainly limits in conventional planar architectures. These architectures suffer major drawbacks in terms of efficiency due to the compromise between light and carrier collection. This study explores the incorporation of PbS CQDs into the LCCM structures that remove the compromise and boost efficiency. Using three-dimensional Maxwell’s equations solver presents an accurate and time/resource-saving method to optimize the LCCM structures. Based on design criteria that consider fabrication of these cells, optimized structures are found with more than 30% improvement over their planar counterparts. Proof-of-concept cells are also manufactured successfully in methods that have great potential for scale-up. This makes the pursuit of cheap and clean energy one step closer to reality.