Novel Designs of Indium Gallium Nitride Based Intermediate Band Solar Cells Through Graded Structures

Student: Manal Aldawsari

Degree: Ph.D., August 2020

Major Professor: Dr. Morgan Ware

Research Area(s):

Nanoscience & Engineering

Photonics

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Background/Relevance

  • Single junction solar cells reached their maximum theoretical efficiency so other materials and novel structures must be established.

  • InGaN has a direct band gap from 0.7 eV to 3.4 eV that covers the solar spectrum and the novel designs of InGaN solar cells through graded structures will enhance the photovoltaic performance.

Innovation

  • Use graded layer starting with GaN and grade down to InN Then, reverse the grading going up to InGaN.

  • Use graded composition multiple quantum wells (MQWs) layer.

Approach

  • Deposit InGaN on sapphire substrates using MBE.
  • Fabricate InGaN solar cells using photolithography techniques, wet etching, and metallization.
  • Structure characterization using atomic force microscopy (AFM), and transmission electron microscopy (TEM).
  • Photoluminescence (PL) measurements and Current-Voltage measurements.
  • Absorbance, Reflectance and Transmission spectroscopy measurements will be performed.
  • External quantum efficiency measurements and the efficiency of the solar cells will be measured.

Key Results

  • Worked with Dr. Ware’s team to develop proof of concepts.
  • Studying the effect of dopant concentration on the band diagram and the solar cell performance
  • Optimizing EQE measurements and optical characterization of Ga2O3 and GaN.
  • Low temperature PL and XRD for thick graded InxGa1-xN.
  • Surface chercterization using AFM and SEM.
  • Nextnano3 simulation for the band diagram of graded InGaN/GaN structure.

Conclusions

  • The graded composition multiple quantum wells layer leads to a reduction in both the potential barrier near the p-Ga and the polarization field which improves the power conversion efficiency.

  • The novel design of the graded layer will enhance the light-generated carriers absorption due to the novel grading design and the absence of the front contact. Using only back contact will allow more light to be absorbed in this solar cell structure.

Future Work

  • Growth of InGaN using MBE

  • Optical & electrical characterization