Células solares de puntos cuánticos coloidales

Abstract

Scarcity of oil reserves together with the increasing environmental awareness are motivating the scientific community to dedicate much effort toward the development of new technologies for producing energy from renewable sources, including photovoltaics. So far, the main handicap of this technology is the high economical cost, therefore the researchers are focusing on the development of cheaper materials and innovative technologies. Among all the available materials, colloidal quantum dots are expected to be excellent candidates for photovoltaics,due to the combination of low-cost processing, high extinction coefficients, band-gap tunability and relatively high stability. The present work focuses on the study of the working principles of quantum dot based solar cells in the solid state (without liquid electrolytes), by following a standard procedure to prepare the corresponding devices in a reproducible and systematic way. Different samples have been prepared under different conditions and treatments to elucidate their effect on the performance of the devices, which were characterized using different optoelectronic techniques. Devices are prepared on basis to the typical depleted heterojunction configuration (Figura 1), which consists of a mesoporous electron transport layer (TiO2) deposited on a conductive glass (FTO), a PbS quandum dot layer and finally a metalic contact (Au) evaporated on the top. In order to reduce the number of short-circuited devices, a compact layer of TiO2 was included between the mesoporous TiO2 layer and the FTO. The nanostructured TiO2 electrode was functionalized with organic ligands, which promoted an improvement on the FF values and consequently, a significant increase of the device efficiency. Moreover, several parameters such as the amount of photoactive material, the significance of using a mesoporous layer of TiO2 or the effect of the nature of the inter-dot ligands, among others, were studied and optimized. After the realization of this work, we were able to prepare devices in a reliable and systematic manner with maximum efficiencies of 2,1%.