Dye-sensitized solar cells provide a cheap alternative compared to solar arrays currently available on the market. However, efficiency issues limit their economic viability. Previous studies have shown excited state lifetimes of photoexcited dye molecules to be several orders of magnitude longer than the timescale for electron transfer to acceptor states in the semiconductor. This would suggest that all dye molecules should be able to inject, but some photoexcited dye molecules continue to relax through the emission of a photon instead of electron injection. Localized acceptor states, where dye molecules inject into specific acceptor states, have been proposed as one cause of this observation. It has been suggested that photoinjected electrons could remain in an acceptor state and prevent the future injection of an electron. Previous intermittent light studies on devices made with anthocyanin dye and TiO<sub>2</sub> films revealed a hysteresis where the kinetics of photocurrent growth and decay after the shutter was opened or closed depended on the length of time the device was under illumination or in the dark. This study further investigates this hysteresis by exploring different combinations of on/off illumination times as well as the influence of lithium in the electrolyte solution by varying the concentration of lithium perchlorate used to make the devices. The resultant photocurrent decays and growths are fit with a bi-exponential decay model. The lifetimes between the different on/off illumination times are compared as well as trends observed from the effects of the varying electrolyte lithium concentrations.

Hysteresis of photocurrent decay and growth in dye-sensitized solar cells under intermittent light

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.