Enhanced performance of CdTe quantum dot sensitized solar cell via anion exchanges

• Eco-friendly synthesis of CdTe/CdS QDs is developed through an anion exchange.
• Light harvesting is increased due to the extension of light absorption range.
• Charge recombination is reduced while charge transport and collection is improved.
• A power conversion efficiency of 2.44% is achieved which is 15 times that of CdTe based QDSSC.

We report on an eco-friendly way to prepare CdTe/CdS quantum dots for quantum dot sensitized solar cell (QDSSC). CdTe/CdS quantum dots are synthesized through an anion exchange between CdTe quantum dots (QDs) and S2− in aqueous solution at low temperature under ambient condition. The resultant QDs are bonded onto TiO2 with the help of thioglycolic acid bifunctional molecule. The uniform distribution of QDs throughout the TiO2 mesoporous film depth is confirmed by the energy dispersive X-ray (EDX) elemental mapping. Absorption, dark current, impedance spectroscopy, and intensity-modulated photocurrent analyses prove that anion exchange can efficiently extend the absorption range, suppress the charge recombination, increase the electron injection as well as accelerate the electron transportation in the cell. In combination with CdS post-treatment, a solar-to-energy conversion efficiency of 2.44% is achieved for CdTe/CdS QDSSC, which is more than 15 times that of the CdTe based cell.

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