Balancing Conductive Network Continuity and Out-of-Plane Transport Barrier in PEDOT:PSS/Ga2O3 Self-Powered Solar-Blind Photoelectrochemical Photodetectors

To realize self-powered solar-blind ultraviolet (UV) photodetectors with high stability, high efficiency, and low cost, a self-powered photoelectrochemical (PEC)-type hybrid UV photodetector was constructed based on a poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)/Ga2O3 organic–inorganic heterojunction. The PEDOT:PSS layer serves not only as a p-type hole transport layer but also as an interface modification layer to modulate charge separation and surface recombination in Ga2O3. As the spin-coating speed decreases, the PEDOT:PSS film thickness increases monotonically from 33.27 to 44.18 nm. Thicker films develop a more continuous conductive network, which favors hole transport. However, additional insulating PSS lamellae also accumulate in the vertical direction, creating a higher out-of-plane transport barrier that counteracts this improvement. The device with an intermediate film thickness of 36.50 nm achieves the optimal balance between these two competing factors, delivering a responsivity of 20.6 mA/W and a specific detectivity of 1.36 × 1010 Jones under 267 nm illumination at zero bias, along with a high UV/visible rejection ratio of 3.18 × 105 and fast rise/decay times of 26/10 ms. This work provides a facile interface engineering strategy for low-cost, high-performance self-powered solar-blind UV photodetectors.