Miconanotecnologia: aplicações em células solares de terceira geração

Abstract

The development of green techniques in the synthesis of nanoparticles is of great importance to potentialize the application of such nanostructures in several areas of knowledge. Nanoparticles of semiconductor materials with diameters less than 100 nm are called quantum dots and have optical and electronic properties depending on their size. In this work, the green synthesis of CdS quantum dots was performed using the pigment-producing fungi Fusarium oxysporum and Penicillium flavigenum in order to apply both the produced pigments and the biosynthesized nanostructures in hybrid solar cell prototypes, that is, sensitized by pigments and quantum dots. The fungi were cultivated in suitable liquid culture media for the production of their characteristic pigments and, in the synthesis of quantum dots, both fungal biomass and pigmented broth containing the fungal metabolites were used, so that the nanostructures synthesized by the pigmented culture broth were used were dispersed in it and could be extracted along with the pigment. Hybrid solar cell prototypes were built using FTO conductive glasses with an area equal to 16cm² and TiO 2 nanoparticles and the polymer HPMC were used in the construction of the films. The electrolyte consisted in a solution of I – /I 3 – and the counter electrode was formed by candle soot. As sensitizing agents, extracts containing, separately, the biosynthesized CdS quantum dots and pigments produced by fungi, as well as the solution of pigments and quantum dots extracted in one step, were used. The CdS nanoparticles showed fluorescence when expo- sed to UV radiation, presented characteristic absorption and IR spectra and revealed, through TEM analysis, uniform distribution, predominant spherical shape and sizes ranging from 2 to 11nm. Tests carried out using a multimeter on clear skies and sunny days revealed that prototypes sensitized only by CdS quantum dots produced an open circuit voltage between 157mV and 280mV, while prototypes sensitized by fungal pigments produced voltages ranging between 179mV and 310mV. Finally, prototypes sensitized by quantum dot extracts and pigments reached the voltages from 447mV to 615.5mV, thus indicating that the combination between the CdS inorganic nanoparticles and fungal pigments revealed a greater light absorption than the other two techniques used in this work. This is due to the broadening of the Sun’s light absorption spectrum provided by the hybridization of the quantum dot structure and fungal pigments.