Theoretical Models and Technologies for Quantum Dots Based Third Generation Solar Cells

H. I. Ikeri, A. I. Onyia, V. M. Adokor

quantum dot, intermediate band, multiple junction, multi exciton generation, quantum confinement, solar cells, solar energy.

Theoretical models and technologies for efficient design of high performance quantum dots (QDs) based solar cells are presented. The obtained models indicate that QDs exhibit bandgap tunability, discrete electronic state and large surface area to volume ratio due to the confinement of photo excited carriers which permit the engineering of their optical and electro-optical responses. These novel properties expanded dramatically absorption of light over a broad spectrum of solar radiation wavelengths in contrary to bulk materials and have paved way for state–of–the-art solar cell technological design architectures via intermediate band, multiple exciton generation and multiple junction solar cells. These mechanisms have been shown to drive quantitative gains in the efficiency of energy conversion scenarios to surpass the Shockley and Quisser limit imposed on conventional cells. Intermediate band solar cell allows for the sub bandgap photons absorption that are loss in the conventional device, thus photon energy less than the fundamental band gap energy can be used to promote charge carriers through the artificially generated optical transition pathways. The multiple exciton generation allows for absorption and utilization of supra bandgap photons that would otherwise be dissipative losses to generate more carriers thereby minimizing the hot carrier thermerlization that characterized the conventional device. Multiple junction solar cells enhance absorption of solar energies over a wide range for full spectrum solar cell through stacking of QDs of appropriate sizes. These exciting advances produce significant increase in solar to electricity conversion efficiencies in the form of increased photo generated currents and voltages.