Photoelectrochemical characterization of n-type and p-type thin-film nanocrystalline Cu2ZnSnSe4 photocathodes

• n- and p-type CZTSe nanocrystals were synthesized by controlling the Zn/Sn ratio.
• Photoelectrochemical (PEC) characteristics of resulting electrodes were compared.
• n-type CZTSe had higher solar conversion efficiency of 2.81%.
• The flat band potential was −0.55 V for n-type CZTSe.
• H2 (94.94%) was the main product of n-type CZTSe PEC cells.

Copper–zinc–tin–selenide (Cu2ZnSnSe4, CZTSe) nanocrystals that do not contain any toxic elements and are 20–25 nm in size are synthesized through a process involving reactions of the elemental sources in a polyetheramine solution. By controlling the Zn/Sn ratio, both n-type and p-type CZTSe nanocrystals could be synthesized. The photoelectrochemical (PEC) properties of electrodes formed using inks containing n-type and p-type CZTSe nanocrystals are compared. An aqueous solution of NaCl is used as the electrolyte. A PEC cell based on an n-type CZTSe photoanode exhibits an efficiency, ηc, of 2.81%, while a p-type cell exhibits ηc of 0.42%. The flat band potentials of the n-type and p-type CZTSe photoanodes in 1 M NaCl are −0.55 and 0.48 V, respectively. Finally, the net carrier concentrations of the n-type and p-type CZTSe photoanodes, calculated from their Mott–Schottky plots, are 3.38 × 1018 and 2.73 × 1018 cm−3, respectively.

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