Symmetry considerations in the empirical k.p Hamiltonian for the study of intermediate band solar cells

With the purpose of assessing the absorption coefficients of quantum dot solar cells, symmetry considerations are introduced into a Hamiltonian whose eigenvalues are empirical. In this way, the proper transformation from the Hamiltonian’s diagonalized form to the form that relates it with Γ-point exact solutions through k.p envelope functions is built accounting for symmetry. Forbidden transitions are thus determined reducing the calculation burden and permitting a thoughtful discussion of the possible options for this transformation. The agreement of this model with the measured external quantum efficiency of a prototype solar cell is found to be excellent.

Graphical AbstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Refined empirical k.p four band Hamiltonian with symmetry considerations. ► Group representation theory used for recipes for forbidden optical transitions. ► Wide discussion of the approximations involved. ► Detailed calculation of the sub-bandgap photon absorption. ► Excellent agreement between calculated and measured internal quantum efficiency.