The Binding Energy and Dynamics of Charge Transfer States in Non-fullerene Organic Solar Cells
Yifan Dong a, Hyojung Cha a, Jiangbin Zhang b, Ernest Pastor a, Pabitra Shakya Tuladhar a, Artem Bakulin a, James Durrant a
a Department of Chemistry and Centre for Processable Electronics, Imperial College London, White City Campus, London, W12 0BZ, UK, United Kingdom
b Optoelectronics Group, Cavendish Laboratory, University of Cambridge, UK., J.J. Thomson Avenue, Cambridge, United Kingdom
Proceedings of Online International Conference on Hybrid and Organic Photovoltaics (OnlineHOPV20)
Online, Spain, 2020 May 26th - 29th
Organizers: Tracey Clarke, James Durrant, Annamaria Petrozza and Trystan Watson
Poster, Yifan Dong, 125
Publication date: 22nd May 2020

Recent progress in organic photovoltaics (OPVs) has been enabled by optimization of the energetic driving force for charge separation, and thus maximization of open-circuit voltage, using non-fullerene acceptor (NFA) materials. In spite of this, the carrier dynamics and relative energies of the key states controlling the photophysics of these systems are still under debate. Herein, I will present an in-depth ultrafast spectroscopic study of a representative OPV system based on a polymer donor PffBT4T-2OD and a small-molecule NFA EH-IDTBR. Global analysis of the transient absorption data reveals the kinetics of the donor and acceptor excitons, respectively. The extracted kinetics suggest that slow (15 ps) generation of charge-transfer states (CTS) is followed by significant geminate recombination. Using temperature-dependent pump push photocurrent spectroscopy, we estimate the activation energy for the dissociation of bound charge-transfer states in PffBT4T-2OD:EH-IDTBR to be 100 ± 6 meV. We also observe additional activation energy of 14 ± 7 meV, which is assign to the de-trapping of mobile carriers. These results provide a comprehensive picture of photophysics in a system representing the new generation of OPV blends with a small driving force for charge separation.

I would like to thank the Optoelectronics Group at the University of Cambridge for sharing the Global analysis codes. 

© Fundació Scito
We use our own and third party cookies for analysing and measuring usage of our website to improve our services. If you continue browsing, we consider accepting its use. You can check our Cookies Policy in which you will also find how to configure your web browser for the use of cookies. More info