Reduced recombination with an optimized barrier layer on TiO in PbS/CdS core shell quantum dot sensitized solar cells

Fast electron transport and slow interfacial electron recombination are indispensable features for efficient photo-electrodes of quantum dot sensitized solar cells (QDSSCs). This study reports the methodology to prevent recombination losses in lead sulfide QDSSCs. TiO 2 nano-particles were coated with two different insulating oxide materials (MgO and Al 2 O 3 ). Single- and-double coated barrier layers are used in order to optimize the passivation effect, prevent recombination losses and to obtain high-performance stable QDSSCs when compared to bare TiO 2 . Metal oxides with a high isoelectric point enhance quantum dot adsorption and also increase the TiO 2 conduction band edge. QDSSCs are examined in detail using a polysulfide electrolyte and a copper sulfide (CuS) counter electrode. A solar cell based on a double coating electrode (MgO/Al 2 O 3 ) yielded excellent performance with an efficiency ( ) of 3.25%. The increase in electron transport and the decrease in electron recombination are responsible for the enhanced J SC and V OC of QDSSCs. The electron lifetime with TiO 2 /MgO/Al 2 O 3 was higher than those with bare TiO 2 , TiO 2 /MgO, TiO 2 /Al 2 O 3 and TiO 2 /Al 2 O 3 /MgO leading to a more efficient electronhole separation and slows down electron recombination. A solar cell based on a double coating electrode (MgO/Al 2 O 3 ) on TiO 2 yielded excellent performance with an efficiency ( ) of 3.25%.