Prevention of surface recombination by electrochemical tuning of TiO2-passivated photocatalysts
Abstract
We present a systematic study of photoluminescence (PL) spectroscopy of TiO2-passivated GaAs as a function of electrochemical potential in an ionic liquid solution. We observe a 7X increase in the PL intensity as the GaAs transitions from accumulation to depletion due to the applied potential. We attribute this to the excellent control over the surface Fermi level enabled by the high capacitance of the electrochemical double layer and TiO2. This allows us to control the surface carrier concentration and corresponding non-radiative recombination rate. In addition to photoluminescence (PL) spectroscopy, we also measured the capacitance-potential (i.e., C-V) characteristics of these samples, which indicate flat band potentials that are consistent with these regimes of ion accumulation observed in the photoluminescence measurements. We have also performed electrostatic simulations of these C-V characteristics, which provide a detailed and quantitative picture of the conduction and valence band profiles and charge distribution at the surface of the semiconductor. These simulations also enable us to determine the range of potentials over which the semiconductor surface experiences depletion, inversion, and accumulation of free carriers. Based on these simulations, we can calculate the Shockley-Read-Hall recombination rate and model the PL intensity as a function of voltage. We show that this approach allows us to explain our experimental data well.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Oct 02, 2017
- Source ID
- 10.1063/1.4997483
Entities
People
- Bingya Hou
- Fatemeh Rezaeifar
- Guangtong Zeng
- Jing Qiu
- Rehan Kapadia
- Stephen B Cronin
Organizations
- Air Force Office of Scientific Research
- American Chemical Society Petroleum Research Fund
- Army Research Office
- National Science Foundation
- University of Southern California