Fabrication of p-type La: Fe_2O_3 as photocathode via atomic layer deposition

摘要

P-type La:Fe_2O_3 and the n-p junction of Fe_2O_3/La:Fe_2O_3 have been fabricated by ALD technique for its excellent conformability and controllable film growth with low defect densities. La: Fe_2O_3 film is demonstrated withp-type characteristics by Mott-Schottky plots and the hole concentration is calculated ～ 1.97 × 10~(15) cm~(-3). It also obtains a cathodic photocurrent of ～28 μA/cm~2 at -0.8 V vs. Ag/AgCl. When forming the n-p junction of Fe_2O_3/La: Fe_2O_3, it is found that the onset potential exhibits a negative shift of ～150 mV and the photocurrent densities increases from 0.62 mA/cm~2 to 1.31 mA/cm~2 at 0.5 V vs. Ag/AgCl. Generally, the incident photon-to-current conversion efficiency (IPCE) of Fe_2O_3/La:Fe_2O_3 n-p junction reaches ～4.47% at 400 nm. Our results imply that it is desirable to tune the energy mismatch between water splitting potentials and the band edges of Fe_2O_3 by a facile surface modification by forming a solid n-p junction.