Abstract

Unpaired electron spins are unique local probes for elucidating photocurrent generation in organic solar cells as well as redox reactions in polymer batteries. Electron Paramagnetic Resonance (EPR) spectroscopy can thus be employed to analyse these processes, identify loss mechanisms, and eventually help developing strategies for improving the performance of devices for energy conversion and energy storage. The first part of this presentation will give an overview about how EPR -based techniques in combination with optical excitation can usefully complement all -optical experiments in studying charge separation in materials for solar cells based on organic semiconductors. As one example, I will discuss the EPR properties of intermediate paramagnetic states generated upon fission of one singlet exciton into two separated triplet excitons. This singlet fission process provides the possibility of building solar cells with quantum efficiencies exceeding 100 %. The second part of the talk will address the role of electron spins in charging and discharging of organic radical batteries (ORBs). In particular, I will report on the development of a versatile on- substrate electrode setup for spectroelectrochemical EPR measurements on redox conductive polymers for ORBs. This setup was recently used to perform quantitative in- operando EPR experiments on electrochemical cells with a novel nitroxide-containing polymer as active electrode material.