Tunable energy band gap of Pb1-xCoxS quantum dots for optoelectronic applications

Abstract

Tuning the energy band gap (Eg) of ternary alloyed Pb1-xCoxS quantum dots (QDs) is studied. Alloyed Pb1-xCoxS (x: 0, 0.1, 0.2, 0.3 and 0.4) QDs were deposited onto TiO2 electrodes for optoelectronic applications using a chemical method. The morphology of the prepared QDs photoanodes has been investigated using a scanning electron microscope (SEM). The structural properties were measured using an X-ray diffractometer and an energy dispersive X-ray (EDX) technique. The optical properties of the prepared Pb1-xCoxS QDs photoanodes are studied using a UV–visible spectrophotometer. The energy band gap of the prepared QDs photoanodes has been tuned through alloying process. To the best of our knowledge, the optical bowing parameter (b) of the alloyed Pb1-xCoxS has been determined using Vegard's law and equals 1.39 eV ± 0.09 eV for the first time. The prepared Pb1-xCoxS QDs photoanodes were used to fabricate quantum dots sensitized solar cells (QDSSCs). Bare PbS (x = 0) QDs act better sensitizers for solar spectrum than alloyed Pb1-xCoxS QDs in QDSSCs. This result is attributed to the decrease in both the absorption and electrons’ injection rates together as x increases from 0 to 0.4. Alloyed Pb1-xCoxS QDs may play good candidates in other optoelectronic applications.