Time-resolved microwave conductivity of P25 TiO2: Distinguishing light-induced electron and hole transport

Time-resolved microwave conductivity measurements were carried out on P25 TiO 2 powder, dry and wetted with ethanol and water, at room temperature with pulsed laser excitation at 360 nm. Using a power-law model, major channels of the charge relaxation kinetics were distinguished and identified. These are related to recombination of (1) electrons with holes trapped on shallow bulk defects and (2) electrons released from surface/bulk states with deeply trapped holes. The shallow bulk traps form a reservoir of energy in equilibrium with the continuous band states preserving the plasma-like charges recombination during ∼200 ns after the excitation. On a longer μs-ms timescale the recombination slows down because of the deep hole traps population, matching the power law kinetics. • Photoinduced charge carrier kinetics was measured in TiO 2 powders with TRMC method. • Power-law model based on shallow and deep band tail states population was proposed. • Two major channels of charge relaxation kinetics were distinguished and identified. • Free electrons and holes recombine in equilibrium with those in shallow traps. • Electrons released from surface/bulk states recombine with deeply trapped holes.