Single Semiconductor-Based Photocurrent Switching via Light Intensity for Selective Biosensing

The mechanism behind photocurrent generation is essential for tuning photoelectrochemical properties of semiconductors and fabricating related devices. As a basic parameter, the photocurrent polarity has been exploited for information processing and can be regulated by constructing suitable interfaces/junctions of semiconductors, tuning external bias potential, or light wavelengths. Nonetheless, light intensity is generally thought to affect only the photocurrent intensity rather than the photocurrent polarity. Here, we report a universal strategy to modulate the photocurrent polarity of a single semiconductor-based photoelectrode by light intensity. Photoelectrochemical kinetic measurements revealed that the surface states, bias potential, and light intensity jointly played crucial roles in the process of photogenerated carrier transfer, thus determining the photocurrent polarity. Based on the different charge transfer pathways produced simply under light of different intensities, a highly selective PEC sensing platform was demonstrated for dopamine detection without any sophisticated biorecognition processes.