InGaN quantum dot superlattices as ratchet band solar cells

We investigate the construction of ratchet band solar cells using InGaN quantum dots. The piezoelectric potentials can spatially separate electron and hole states in InGaN quantum dots. This spatial separation reduces both radiative and non-radiative recombination within the quantum dot, providing one of the key characteristics of a ratchet band system. Ratchet band solar cells have proven difficult to realize experimentally, and the piezoelectric potential in InGaN quantum dots could provide a spatial ratchet that can operate at room temperature with broadband absorption. We use a k.p model to calculate the electronic structure and absorptance of a superlattice of InGaN/GaN quantum dots. We present a new method to calculate the absorptance for the bound-to-continuum transition by using bulk k.p states to approximate the host material continuum states. We show an example of an InGaN quantum dot that could act as a ratchet band solar cell, using its spatially separated states to reduce recombination within the quantum dot.