SKM 2023 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 1: Focus: Organic Solar Cells Based on Non-fullerene Acceptors: Loss Mechanism and Options for Above 20 % Efficiencies I

CPP 1.6: Talk

Monday, March 27, 2023, 11:00–11:15, GÖR 226

Direct Determination of the Photogenerated Free Charge Carrier Luminescence in Organic Solar Cells via Transient Photoluminescence Measurements — •Jared Faisst, Mathias List, and Uli Würfel — Fraunhofer ISE, Freiburg, Deutschland

Photoluminescence (PL) measurements have shown to be a valuable tool characterizing the optoelectronic properties of semiconductors. In organic solar cells, the PL measurement of free charge carriers is hindered by the strong and spectrally broad luminescence of non-dissociated local exciton recombination. Therefore, the PL of free charge carriers under steady state condition is not directly detectable. To overcome this problem, we make use of the vastly different lifetimes of local excitons (ps-ns) and free charge carriers (µs). In this work, we present experimental time resolved PL data of a fullerene based D18:PC₇₁BM and two non-fullerene based D18:Y6 and PV-X plus organic solar cells and demonstrate the possibility to separate the luminescence of local excitons from the one of free charge carriers. We further show that the luminescence of the free charge carriers indeed correlates with the quasi-Fermi level splitting as expected. Hence, this novel measurement technique eventually allows to investigate free charge carriers in organic absorber layers directly. This is of great importance to further understand recombination mechanisms and degradation effects and to identify optimization potentials.