Development and Characterization of Sub-Monolayer Quantum Dot (QD) IBSCs

Student: Najla Alnami

Degree: Ph.D., December 2019

Major Professor: Dr. Gregory Salamo

Research Area(s):


Nanoscience & Engineering

View Research Quadslide


  • Experimental efforts towards fabricating high efficiency and low cost intermediate band solar cells (IBSCs) have not met the predictions of theoretical efficiency of 63%.
  • A novel design of intermediate band solar cells is needed for increasing the solar cell conversion efficiency by increasing the solar cell photocurrent while preventing the reduction of open circuit voltage.


  • Developing and optimizing IBSCs based on sub-monolayer QDs.
  • Investigating the behavior of the solar cell when the island size is varied, when the cells are doped at different doping concentrations, and when the number of sub-monolayer quantum dot (QD) stack are varied.


  • Growing sub-monolayer QDs and optimizing the growth using MBE.
  • Incorporate sub-monolayer QDs in IBSC structures.
  • Fabricating the proposed IBSC structures using standard optical photolithography, wet etching, and metallization.
  • Study the structural, optical, and electrical characteristics of the structure using: Atomic Force Microscopy, Transmission Electron Microscopy, Solar Power Conversion Efficiency measurement, External Quantum Efficiency measurement, PL measurement, and Absorption Spectroscopy.

Key Results

  • Growing a reference sample without sub-monolayer QDs.
  • Optimizing the fabrication process of the grown IBSCs.
  • The designed sub-monolayer
  • QD IBSC structure


  • The rapid increase in intermediate band solar cell efficiency is a promising sign of the possibility of developing a commercially practical solar cell system. The IBSC in this research is designed to overcome the current IBSC limitations.

Future Work

  • Developing and optimizing the growth of sub-monolayer QDs.
  • Investigating the behavior of the intermediate band when the sub-monolayer QD size is varied, the QDs are doped at different doping concentrations, the number of sub-monolayer QDs stack are varied.
  • Studying the structural quality growth,  electrical, and optical behavior of the proposed structure.