SIMULATION AND THEORETICAL ANALYSIS OF QUANTUM DOT SOLAR CELLS

Abstract

Solar cell works on the principle of photovoltaic which converts solar energy to electric energy. This thesis is based on simulation and theoretical analysis of quantum dot solar cells having Gallium Arsenide (GaAs) direct band gap material instead of conventional silicon which is indirect gap material and self-assembled Indium Arsenide (InAs) quantum dots (QDs) embedded inside the middle part of intrinsic layer of p-i-n structured solar cell which improves overall efficiency of solar cells up to 24.72% because limitations of conventional single junction solar cell is that it does not absorbs low energy photons to generate electron hole pairs thus these photons is not contributing in the device current and photons having high energy is not used efficiently as high energy photon generates hot carriers. In this work we proposed quantum dot (QD) intermediate band solar cell which absorbs photons having low energy in infrared region and contribute in the device current which increases external quantum efficiency of solar cell while maintaining open circuit voltage almost constant. We also increased intrinsic layer in the structure and found that only increasing intrinsic layer short circuit current of device increases while open circuit voltage increases negligibly. Size of quantum dots, spacing between adjacent quantum dots and barrier material that separate two layers of quantum dot is challenging task, we used 5*10nm size of InAs, barrier material layer which is intrinsic GaAs of thickness 12.5nm and space between two adjacent filled with intrinsic GaAs is of 10nm width. Position of these quantum dots in intrinsic layer plays important role to increase external quantum efficiency (EQEs), we have placed these layers at middle of intrinsic layer. For all these simulation we used Silvaco Atlas TCAD software and got plots on Tony Plot.