- Nagai Group
Organic Photocatalyst: Reducing energy loss A combination of materials that reduces energy loss in organic solar cells has been identified by researchers in Japan. A solar cell comprises two materials: one with excess electrons and one with absent electrons, referred to as holes. An incoming photon can create an electron-hole pair. These separate at the material's interface and flow in opposite directions to generate a current. Energy is lost as the electric potential difference across the interface is smaller than the energy of the photon. Keiji Nagai and colleagues from the Tokyo Institute of Technology used a technique called scanning Kelvin probe microscopy to investigate this potential difference between two organic materials. They identified a naturally occurring electric potential at this interface, which reduces the potential difference between the materials and thus energy loss during photon conversion.
"Enhanced Oxidation Power as Photoelectrocatalysis based on Micrometer-Localized Positive Potential in Terrace Hetero p-n Junction" NPG Asia Mater., 10 (7), 630-641, (2018). DOI 10.1038/s41427-018-0058
Scheme for experimental setup of bilayer and dot terrace bilayer film photocatalyst to decompose 3 wt% aqueous solution of acetic acid into CO2 under monochromatic light irradiation (lamda = 630 nm, intensity = 1 mW/cm2). The dot terraced bilayer H2Pc/PTCBI/Teflon membrane was prepared with diameter of each H2Pc dot = 200 µm, pitch = 200 µm. Membrane size 0.6 cm x 0.6 cm. Thickness for each of PTCBI and H2Pc was 50 nm. The control sample was a container without any film which is kept under the dark condition. Light irradiation was from H2Pc side. Irradiation time was 1h. The result from the gas chromatography analysis is shown for the amount of CO2 evolution (in mol) and EQE (in %). The amount of CO2 in the blank sample was 1.70 µmol and the value was zeroed to be the baseline value for the bilayer and the dot terrace bilayer film.