Effects of Cu content on the photoelectrochemistry of Cu2ZnSnS4 nanocrystal thin films

• Two compositions of CZTS were synthesized, one yielding Cu-poor and the other Cu-stoichiometric nanocrystals (NCs).
• Physical and electronic properties of both films were probed using various analytical techniques.
• Films comprised of Cu-poor CZTS showed tighter packing with less defects compared to those of stoichiometric-Cu.
• Photoelectrochemical measurements exhibited increased photoconversion and increased photostability of the Cu-poor films.
• Intensity modulated photocurrent spectroscopy showed that the Cu-deficient NCs had half the recombination rate as that of stoichiometric-Cu films.

Cu2ZnSnS4 (CZTS) nanocrystals (NCs) were prepared via a one-pot solvothermal method. Given that the composition affects the electronic properties of this p-type semiconductor, two compositional ratios were chosen from 10 designed and synthesized analogues, one yielding Cu-poor and the other Cu-stoichiometric CZTS. NCs in which the Cu concentration was slightly below stoichiometric yielded more uniform films with greater photovoltaic performance. The lower Cu content also lead to slightly better crystallinity within the film, as demonstrated by XRD, Raman spectroscopy and transmission electron microscopy. Chronophotoelectrochemical measurements indicated that both types of NC films displayed good stability; however, with a decrease in potential, an increase in resistance for the Cu-stoichiometric film was observed. As determined by intensity modulated photocurrent spectroscopy, the product separation rate of the photoinduced holes and electrons in the Cu-poor films were more than 3 times that of the Cu-stoichiometric, confirming that the lower Cu content led to an improved photoperformance.

Figure optionsDownload as PowerPoint slide