Effect of elastic strain on band edge alignment and position of intermediate band of isolated and coupled quantum dots

Solar cells with quantum dot nanostructure absorbing medium have a potential to overcome single junction limit and achieve the solar energy conversion efficiency up to 63%. Self-assembled quantum dots that are grown by using molecular beam epitaxy(MBE) or metal organic chemical vapor deposition (MOCVD) have significant effect of strain on the band edge alignment and hence the confinement potential of electrons and holes. The energetic positions of confined energy states in quantum dots, which, act as intermediate state or band in intermediate band solar cells (IBSCs) are strongly affected by the strain in and around a quantum dot (QD). This work is focused on the calculation of strain distribution and its effect on band structure of QD array for its potential application in quantum dot intermediate band solar cells (QDIBSCs). Strain distribution in and around a QD is calculated using continuum theory of elasticity. When the inter-dot distance in the growth direction is sufficiently close, there is the interaction in strain distribution of QD layers. The strain distribution due to a vertically aligned QD array is calculated from superposition of the strain due to single quantum dot. The strain calculated this way is given as input for the calculation of band edge alignment and the position of QD confined states.