Improved light-harvesting and suppressed charge recombination by introduction of a nanograss-like SnO 2 interlayer for efficient CdS quantum dot sensitized solar cells.

Quantum dot sensitized solar cell (QDSSC) performance is primarily limited by the recombination of charges at the interfaces of TiO 2 /quantum dot (QD) sensitizer/electrolyte. Hence, blocking or suppressing the charge recombination is an essential requirement to elevate the QDSSC performance to the next level. To retard the charge recombination, herein, we propose the introduction of a SnO 2 nanograss (NG) interlayer on the surface of TiO 2 using the facile chemical bath deposition method. The SnO 2 NG interlayer not only inhibits the interfacial recombination processes in QDSSCs but also enhances the light-harvesting capability in generating more excitons. Hence, the TiO 2 /SnO 2 NG/CdS QDSSCs can achieve the power conversion efficiency of 3.15%, which is superior to that of a TiO 2 /CdS device (2.16%). Electrochemical impedance spectroscopy, open-circuit voltage decay and dark current analyses confirm that the recombination of charges at the photoanode/electrolyte interface is suppressed and the life time is improved by introducing the SnO 2 NG interlayer between the TiO 2 and CdS QD sensitizer.