Abstract
In the present work, we report the use of bacterial cells for the production of CdS/CdSe Core/Shell quantum dots (QDs), a complex nanostructure specially designed to improve their performance as photosensitizer in photovoltaic devices. The method requires the incorporation of L-cysteine, CdCl2 and Na2SeO3 to Escherichia coli cultures and allows a tight control of QDs properties. The obtained CdS/CdSe QDs were photophysically and structurally characterized. When compared to CdS QDs, the classical shift in the UV-visible spectra of Core/Shell nanostructures was observed in CdS/CdSe QDs. The nanosize, structure, and composition of Core/Shell QDs were confirmed by TEM and EDS analysis. QDs presented a size of approximately 12 nm (CdS) and 17 nm (CdS/CdSe) as determined by dynamic light scattering (DLS), whereas the fourier transform infrared (FTIR) spectra allowed to distinguish the presence of different biomolecules bound to both types of nanoparticles. An increased photostability was observed in CdS/CdSe nanoparticles when compared to CdS QDs. Finally, biosynthesized CdS/CdSe Core/Shell QDs were used as photosensitizers for quantum dots sensitized solar cells (QDSSCs) and their photovoltaic parameters determined. As expected, the efficiency of solar cells sensitized with biological CdS/CdSe QDs increased almost 2.5 times when compared to cells sensitized with CdS QDs. This work is the first report of biological synthesis of CdS/CdSe Core/Shell QDs using bacterial cells and represents a significant contribution to the development of green and low-cost photovoltaic technologies.
Highlights
During the last decade, the interest in replacing fossil fuels with non-conventional renewable energies (NCRE) has grown worldwide (Hoekstra and Wiedmann, 2014)
We developed a CdS/CdSe quantum dots (QDs) biosynthesis method based on the use of L-cysteine, CdCl2, and Na2SeO3
The biosynthesis of CdS/CdSe QDs was divided in 2 steps: First, the synthesis of the CdS core and the production of the CdSe shell
Summary
The interest in replacing fossil fuels with non-conventional renewable energies (NCRE) has grown worldwide (Hoekstra and Wiedmann, 2014). The second generation of solar cells, based on thin layers of semi-conductor materials (mainly metal alloys made of Cu, In, Ga, and As), in general present similar efficiencies and slightly lower production costs, this technology still have a high environmental impact (Green et al, 2015). As a response to these requirements the third generation of solar cells emerged, especially the quantum dot sensitized solar cells (QDSSCs) (O’Regan and Grätzel, 1991; Grätzel, 2003; Rühle et al, 2010; Jun et al, 2013; Pan et al, 2018) This type of solar cell displays the lowest rates of sulfur oxide, nitrogen oxide and carbon dioxide emission compared to other photovoltaic technologies (Tyagi et al, 2013). Depending on the QD composition and nanostructure of the TiO2 layer, the efficiency range goes between 0.003 and
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