Surface States-Induced Light Intensity-Dependent Bipolar Photoelectrodes for Selective Sensing

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 could be regulated by selecting suitable types of semiconductors, external biased potential, or photo energy. Nonetheless, the 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 by light intensity, which was also verified by four different semiconductors. The photoelectrochemical kinetics measurements disclosed that the surface states and light intensity jointly played a crucial role in the process of photogenerated carriers transfer, thus determining the photocurrent polarity. Base on the different charge transfer pathways produced under different illumination, a highly selective PEC sensing platform was constructed to specifically recognize dopamine without any modification process.