(Invited) Tuning the Optoelectronic Properties in Composite Systems for Sunlight Conversion

Abstract

The processes of light absorption, exciton generation, charge separation and collection are critical to a series of applications, in which Sun light is either directly converted into electric power, like in solar cells, or transformed into chemical energy, like in photoelectrochemical hydrogen generation. All these processes are regulated by the optoelectronic properties of complex systems, in which the electronic band structure can be finely tuned by proper adjustment of chemical composition, size and morphology of the single components. Key element for the control of the optoelectronic properties is the modulation of the final electronic band structure. We will illustrate different strategies to obtain the desired optical and electrical properties in different complexes.One of the most interesting systems is composed of semiconducting nanocrystals exhibiting quantum confined effects (the so-called quantum dots, QDs), which act as light absorbing materials, and generate excitons as a consequence of photon absorption. [1] The QDs are typically coupled to a wide bandgap semiconductor (SnO2, ZnO, TiO2), which acts as electron transport material. In this case, the optoelectronic properties are determined by the dynamics of hole/electron dissociation and recombination, and the structure of the interface between the QD and the oxide semiconductor regulates such dynamics. Another option is to apply core-shell QDs, in which the relative band alignment between the core and the shell can be tuned by tailoring the interface between them. [2]We will illustrate a series of examples, [3] in which exciton dynamics in composite systems influences the functionality of the final device, including solar cells, photoelectrochemical hydrogen production and luminescent solar concentrators. Keywords: Composite systems; quantum dots; exciton dynamics; solar cells; photoelectrochemical hydrogen generation; luminescent solar concentrators