In this paper, we present calculations of the absorption coefficient for transitions between the bound states of quantum dots grown within a semiconductor and the extended states of the conduction band. For completeness, transitions among bound states are also presented. In the separation of variables, single band k-p model is used in which most elements may be expressed analytically. The analytical formulae are collected in the appendix of this paper. It is concluded that the transitions are strong enough to provide a quick path to the conduction band for electrons pumped from the valence to the intermediate band.

A comprehensive assessment of the nature of the distribution of sub band-gap energy states in bulk GaAsBi is presented using power and temperature dependent photoluminescence spectroscopy. The observation of a characteristic red-blue-red shift in the peak luminescence energy indicates the presence of short-range alloy disorder in the material. A decrease in the carrier localisation energy demonstrates the strong excitation power dependence of localised state behaviour and is attributed to the filling of energy states furthest from the valence band edge. Analysis of the photoluminescence lineshape at low temperature presents strong evidence for a Gaussian distribution of localised states that extends from the valence band edge. Furthermore, a rate model is employed to understand the non-uniform thermal quenching of the photoluminescence and indicates the presence of two Gaussian-like distributions making up the density of localised states. These components are attributed to the presence of microscopic fluctuations in Bi content, due to short-range alloy disorder across the GaAsBi layer, and the formation of Bi related point defects, resulting from low temperature growth.

Unlike Type I, Type II quantum dots do not have hole bound states. This precludes that they invade the host semiconductor bandgap and prevents the reduction of voltage in intermediate band solar cells. It is proven here that the optical transition between the hole extended states and the intermediate bound states within the host bandgap is much stronger than in Type I quantum dots, increasing the current and making this structure attractive for manufacturing these cells.

The thermoradiative diode is a novel heat engine that converts athermal radiative emission from a hot converter to a colder environment into work. This stands in contrast to essentially all radiative heat engines realized to date, where an external hot reservoir radiates toward a converter that resides at (and can be reversibly coupled to) a cold reservoir. We derive the fundamental bounds on conversion efficiency and power production for generalized far-field hot-side heat engines with radiative exchange that can be black body (thermal) or, more generally, athermal. This is followed by the corresponding derivation for the rich landscape of performance bounds for the specific case of thermoradiative diodes, including why the Landsberg-efficiency limit associated with heat engines that include radiative exchange can be surpassed, and how the ultimate Carnot-efficiency limit could be approached.

The calculation of the energy spectrum and absorption coefficients of quantum dot nanostructured intermediate band solar cells using the Empiric K • P Hamiltonian method and its agreement with experimental data are summarized. The well established Luttinger Kohn Hamiltonian modified by Pikus and Bir for strained material, such as quantum dot arrays, is presented using a simplified strain field that allows for square band offsets. The energy spectrum and absorption coefficients are calculated with this new Hamiltonian. With the approximations made the energy spectrum results to be exactly the same but the absorption coefficient fits experiments less accurately. The computer time using the latter Hamiltonian is much longer than the former one.