Majority Charge Carrier Transport in Particle-based Photoelectrodes

The inter-particle charge transfer of particle-based photoelectrodes was investigated using a particle-based LaTiO2N photoelectrode as model system. The thickness-dependent front- to back-side illumination photocurrent ratio was measured and compared to the numerical photogenerated current ratio. This comparison suggested the presence of majority charge carrier transport limitations and estimated that only a particle-based film thickness of 450 nm was contributing to the photocurrent. We introduced three different theoretical inter-particle charge transfer mechanisms and implemented their respective equations in a numerical model. The calculated photocurrent-voltage curves were compared to experimental data and proved that inter-particle charge transfer is negligible. Only the particles in direct contact with the fluorine doped tin oxide glass substrate were contributing to the photocurrent. Thus, more efficient particle-based photoelectrodes should incorporate efficient conductive networks connecting particles and substrate. The simulations indicate that the photocurrent density of particle-based photoelectrodes could be increased from 1.2 mA cm-2 to 5 mA cm-2 at 1.23 VRHE under front-side illumination when adding such a conductive network between particles and substrate.