Solar energy is becoming one of the primary sources of energy replacing fossil fuels due to its abundance. Its versatility and environmental friendly have made it one of the most promising renewable sources of energy. Photovoltaic conversion of solar energy from the sun is becoming the primary source of energy replacing the depleting fossil fuel. Modeling of solar cells provides an insight into the operation and better understanding of the ways to improve their efficiency; this could also reduce the physical implementation and the cost for fabrication. The 3 dimensional numerical model for GaAs Quantum Dot solar cell has been developed and presented. This work proposes a better way to improve the efficiency of the solar cell by implementing different size (odd) quantum dots. The QD Model utilizes the Schroedinger Equation and the same is validated using simulator tool, Quantum Dot Lab, and the band gap energy of QD is calculated at different temperatures. The results obtained shows good improvement of the efficiency of the solar cell at different wavelengths of solar spectrum.