The 43rd ROEL Lecture Session was held on Aug. 29th. As a guest speaker, Dr. Wei Lek KWAN from Singapore University of Technology and Design, gave us a lecture entitled "Transparent organic photovoltaic – (1) Spray coated PEDOT:PSS as transparent anode for transparent OPV, (2) Improving Voc of NIR dyes by side-chain engineering, is it possible?".
More than 30 researchers and students attended to the lecture, and it finished in success.

Conference room during the lecture

Dr. Wei Lek KWAN, Singapore University of Technology and Design

The 43rd ROEL Lecture Session

There will be 2 parts to the talk, both surrounding a central theme of transparent organic photovoltaic.
In the first part of the talk, I will discuss the issues of coating PEDOT:PSS on a hydrophobic P3HT:PCBM surface. As high conductivity PEDOT:PSS is used as a transparent anode, the thickness and roughness has to be reduced for high transparency. By optimizing the wettability and drying time of the PEDOT:PSS, we were able to attain a spray coated transparent anode without compromising on device performance. A transparent OPV device with close to 60% transparency is achieved.
In the second part of my talk, I will discuss the possibility of using side-chain to improve the Voc of the OPV device. In transparent OPV, NIR dyes are often used due to its transparency in the visible range and strong absorption in the NIR region. Since the LUMO-HOMO gap is usually low for such dyes, the Voc is often very small, thus compromising the device efficiency. Recently, it was discovered that the Voc does not only depends on the difference between the HOMO level of the donor and LUMO level of the acceptor, but also bimolecular recombination and charge transfer states. I will report the use of a novel side-chain to reduce bimolecular recombination, thus improving the Voc of the device.