Atomic layer deposition of NiS and its application as cathode material in dye sensitized solar cell

Abstract

Nickel sulfide (NiS) is grown by atomic layer deposition (ALD) using sequential exposures of bis(2,2,6,6-tetramethylheptane-3,5-dionate)nickel(II) [Ni(thd)2] and hydrogen sulfide (H2S) at 175 °C. Complementary combinations of in situ and ex situ characterization techniques are used to understand the deposition chemistry and the nature of film growth. The saturated growth rate of ca. 0.21 Å per ALD cycle is obtained, which is constant within the ALD temperature window (175–250 °C). As deposited films on glass substrates are found polycrystalline without any preferred orientation. Electrical transport measurement reveals degenerative/semimetallic characteristics with a carrier concentration of ca. 9 × 1022 cm−3 at room temperature. The ALD grown NiS thin film demonstrates high catalytic activity for the reduction of I−/I3− electrolyte that opens its usage as cost-effective counter electrode in dye sensitized solar cells, replacing Pt.