Constructing a full-space internal electric field in a hematite photoanode to facilitate photogenerated-carrier separation and transfer

Hematite (alpha-Fe2O3) material has outstanding advantages in the photoelectrochemical water splitting (PEC-WS) field, while its generally low photogenerated-carrier separation (eta(sep)) and transfer (eta(tran)) efficiencies severely impede its further application. An internal electric field can significantly enhance eta(sep) and eta(tran) efficiencies, but the effective scope urgently needs to be expanded. This work innovatively implements gradient doping into an alpha-Fe2O3 film to achieve a direction-controlled and full-space internal electric field throughout the entire photoanode. The carrier-transport dynamics and density functional theory (DFT) calculations demonstrate that the direction of the internal electric field of an alpha-Fe2O3 photoanode with gradient-decreasing doping is consistent with that of the photoanode/electrolyte junction. The synergy effect between them can substantially enhance the photogenerated-carrier separation and transfer efficiency. Compared with the case of gradient-increasing doping, the alpha-Fe2O3 photoanode with gradient-decreasing doping exhibits the largest saturated photocurrent density and an enhancement of 40.7% (55.2%) for eta(sep) (eta(tran)) at 1.23 V-RHE under AM 1.5G illumination. This work provides a facile and general gradient doping strategy to expand the effective scope of an internal electric field for boosting the photoelectric conversion performance.

Automated summary

This study demonstrates a new strategy of gradient doping to enhance the internal electric field effect in alpha-Fe2O3 thin films, leading to significantly improved photogenerated-carrier separation and transfer efficiencies.