Tailoring the energy band gap of alloyed Pb1−xZnxS quantum dots for photovoltaic applications

In this work, tailoring the energy band gap (E g ) of ternary alloyed Pb 1−x Zn x S quantum dots (QDs) for photovoltaic applications has been investigated. Different zinc molar ratios (x: 0, 0.1, 0.2, 0.3 and 0.4) in Pb 1−x Zn x S QDs were adsorbed onto TiO 2 (titania) nanoporous films using sub-sequential chemical deposition technique. The morphology of the prepared QDs is studied using a scanning and transmission electron microscope. The structural properties were measured using an X-ray diffractometer and an energy dispersive X-ray technique. The optical properties were recorded using a UV–visible spectrophotometer. The optical bowing constant (b) of alloyed Pb 1−x Zn x S has been deduced and equals 1.49 eV. To the best of our knowledge, this is the first time that the bowing constant of alloyed Pb 1−x Zn x S is determined. The photovoltaic characteristics (short circuit current density J sc , open circuit voltage V oc , fill factor FF and energy conversion efficiency η) of the assembled alloyed Pb 1−x Zn x S QDs sensitized solar cells (QDSSCs) are measured under AM1.5 conditions. The optimal photovoltaic parameters of the alloyed Pb 1−x Zn x S QDSSCs were found at x = 0.2. The open circuit voltage decay of the assembled QDSSCs is measured. This novel result is attributed to suppressing of the electron–hole pairs recombination processes.