Wurtzite InGaN/GaN Quantum Dots for Intermediate Band Solar Cells

Wurtzite InGaN quantum dots in GaN are investigated for intermediate band solar cells. A global limiting power conversion efficiency of 44% is predicted through detailed balance calculations with full freedom of allowed subgap transitions. We consider cylindrical quantum dots, predicting band structures using an 8-band k.p model, including deformation potential and piezoelectric fields from induced lattice strain. Taking the energy levels from the k.p model as absorption cutoffs in the detailed balance calculation, we determine the best device efficiency possible as a function of indium fraction and dot size. For small dots, of size ≈ 50 Å and indium fraction ≈ 0.7, efficiencies up to 42% are in principle attainable under 1-sun illumination.