Solid state quantum dot sensitized solar cells based on CdxZn1-xSe sensitizers
Nikolaos Balis a, Georgia Sfyri a, Panagiotis Lianos b
a Engineering Science Dept., University of Patras - Greece, Patras, Greece
b FORTH/ICE-HT, Greece
Poster, Panagiotis Lianos, 009
Publication date: 1st April 2013

Solid state quantum dot sensitized solar cells make an interesting alternative to liquid electrolyte devices. Stability issues are relaxed in the case of solid state cells, which are additionally exempted from electrolyte sealing problems. In this presentation, we will demonstrate the importance of mixed CdxZn1-xSe quantum dots in the construction of semiconductor-sensitized  nanoparticulate titania photoanodes, which are assembled with hole-transporting polymers to make solid state solar cells.  Mixing of Cd with Zn in several cases of metal chalcogenide quantum dots has always produced more efficient devices than single metal components [1,2] and this is once more demonstrated in the present case. It is known that mixture of semiconductors leads to passivation of defect sites while dispersion of photogenerated charge carriers facilitates electron-hole separation. Most works refer to mixed Zn-Cd sulfides and fewer to selenides.  It will be shown that solar cells made of Cd0.7Zn0.3Se give the most efficient cells while pure CdSe and, even worse,  pure ZnSe gave much lower efficiencies.

Solid state devices suffer of  low currents and low fill factors due to limited conductivity, particularly, in the organic hole transporter and limited charge transfer rates at interfaces. Some additives may, however, partially take care of this problem. We will present a protocol of several additives that will fit the materials involved in the present case. One such additive is 2-Amino-1-methylbenzimidazole, which was previously demonstrated to enhance cell electric characteristics [3].

[1] Balis N. et al. Quantum dot sensitized solar cells based on an optimized combination of ZnS, CdS and CdSe with CoS and CuS counter electrodes. Electrochim. Acta 2013, 91, 246– 252 [2] Antoniadou M. et al. Photocatalysis and photoelectrocatalysis using (CdS-ZnS)/TiO2 combined photocatalysts. Applied Catalysis B: Environmental 2011, 107, 188– 196 [3] Balis N. et al. A Solid-State Hybrid Solar Cell Made of nc-TiO2, CdS Quantum Dots, and P3HT with 2-Amino-1-methylbenzimidazole as an Interface Modifier. J. Phys. Chem. C 2011, 115, 10911–10916
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