The utilization of (sun-)light for the conversion of solar energy into either electrical or chemical energy is very popular. Prominent examples are photoelectrochemical water splitting and CO2 reduction or dye sensitized solar cells. Other branches of photoelectrochemistry include the investigation of semiconducting polymers or inorganic semiconductors. Scanning electrochemical microscopy can be combined with a Synchronized Photo- Excitation System to study those materials and processes.

Quantum dots (QDs) can be used to substitute dye sensitizers in solar cells. SECM was used in a high-throughput screening of a binary QD library to identify the most active composition. Instead of a microelectrode, an optical fiber was used to illuminate the sample locally. The photocurrent is detected at the sample which is employed as working electrode.

Yuan, D., Xiao, L., Luo, J., Luo, Y., Meng, Q., Mao, B. W., & Zhan, D.; High-Throughput Screening and Optimization of Binary Quantum Dots Cosensitized Solar Cell. ACS applied materials & interfaces, 2016, 8, 18150-18156.

Photoexcitation from the bottom of the sample through an inverted microscope has the advantage of using a common microelectrode from the top. Microelectrode and illuminated spot are aligned for high precision and high spatial resolution of the experiments. Thin films of photoelectrocatalysts for water splitting can be mapped simultaneously regarding photocurrent at the sample, ORR current at the microelectrode (detection of produced oxygen) and topography via shear force. This way, it is possible to gain multiple information in one scan.

3D Map of Topography by Shear-force Sensing
3D Map of Photocurrents (420nm light)
Distribution of O2 (iORR) from OER

For more information on photoelectrochemical experiments with ElProScan ask for the Photoelectrochemistry brochure.