Improving light absorption and photoelectrochemical performance of thin-film photoelectrode with a reflective substrate.

The charge separation/transport efficiency is relatively high in thin-film hematite photoanodes in which the distance for charge transport is short, but simultaneously the high loss of light absorption due to transmission is confronted. To increase light absorption in thin-film Fe 2 O 3 :Ti, commercial substrates such as Cu foil, Ag foil, and a mirror are adopted acting as back-reflectors and individually integrated with the Fe 2 O 3 :Ti electrode. The promotion effect of the commercial back-reflectors on the light absorption efficiency and photoelectrochemical (PEC) performance of the hydrothermally prepared Fe 2 O 3 :Ti electrodes with a variety of film thicknesses is investigated. As a result, Ag foil and the mirror show favorable and equal efficacy while the promoting effect of Cu foil is limited. In addition, the photocurrent increment achieved by the Ag back-reflector decreases linearly along with the logarithmic of the film thickness and the optimized film thickness of the Fe 2 O 3 :Ti electrode is decreased from 520 to 290 nm. The high durability of Ag foil in the alkaline electrolyte during solar light irradiation is demonstrated. Furthermore, the reflective substrate also shows a promotion effect on the BiVO 4 photoanode and CuBi 2 O 4 photocathode, as well as the unbiased photocurrent from a tandem cell constituted by TiO 2 and CuBi 2 O 4 .