Decreased Surface Photovoltage of ZnO Photoanode Films via Optimal Annealing Temperature for Enhanced Photoelectrochemical Performance

Figure 4

The statistical CPD acquired from KPFM mapping in the dark and under illumination: (a) unannealed ZnO, (b) ZnO-350, (c) ZnO-450, and (d) ZnO-550, respectively. (e) Average CPD in the dark and under illumination to the left scale and SPV of different samples to the right scale. (f) Schematic energy band diagram for the generation of surface photovoltage (SPV) at the ZnO surface (CBM: conduction band minimum; VBM: valence band maximum; : electron affinity). The solid lines and the dotted lines represent the condition in the dark and light, respectively.

(a)

(b)

(c)

(d)

(e)

(f)