(478b) Photoelectrochemistry of Semiconducting Polymers: Engineering Electronic Properties and Charge Carrier Dynamics

A liquid junction photoelectrochemical (PEC) cell is an attractive mean to generate clean and renewable energy (i.e., hydrogen and hydrocarbons) from solar energy. Despite the extensive research in PEC systems using inorganic semiconductors, it remains challenging to develop efficient, stable, and inexpensive PEC systems. Semiconducting polymers are potential candidates satisfying the criteria that materials consist of earth abundant materials and the polymer-based devices can be prepared by low cost and large-scale processing techniques such as inkjet and roll-to-roll printings. Moreover, tunable electronic properties of semiconducting polymers offer an opportunity to develop efficient, stable, and inexpensive PEC systems. Doping of semiconductors is an essential process to control electronic properties of the materials, thus making feasible applications in PEC cells and improving performance of the cells. However, there is a lack of fundamental study of doping to tailor electronic properties of semiconducting polymers for PEC applications. In this study, we discuss doping of p-type semiconducting polymers and their photoactivities in PEC cells. First, irreversible doping is desired for stable PEC operations since doped semiconducting polymers should maintain their electronic properties without unwanted de-doping during the operations. We found that the irreversible doping can be achieved by doping of bulky and/or hydrophilic dopant species into the semiconducting polymer films, leading to significant increases in photoactivities. Secondly, transient photocurrent measurements were conducted to investigate charge carrier dynamics of semiconducting polymers in PEC cells. The detailed understanding on improved photoactivities of doped semiconducting polymers would pave a road to further develop the high-performance polymer-based PEC systems.