Berlin 2012 – scientific programme

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DS: Fachverband Dünne Schichten

DS 34: Organic thin films II: Interface spectroscopy

DS 34.4: Talk

Thursday, March 29, 2012, 15:45–16:00, H 2032

Charge Generation and Recombination in Perylene Solid State Dye-sensitized Solar Cells — •Michael Meister, Ian A. Howard, Yoojin Kim, Henrike Wonneberger, Chen Li, Denis Andrienko, Klaus Müllen, and Frédéric Laquai — MPI für Polymerforschung Mainz

Perylene derivatives have attracted strong interest in replacing the commonly used Ru complexes as all organic sensitizers in solid state dye-sensitized solar cells (sDSCs), since they combine a strong absorption with reasonably good device efficiencies if used with Spiro-MeOTAD as solid state hole transporter. Here we present a photophysical study of promising perylene monoimide dyes (PMI) for sDSCs. By employing time resolved photoluminescence, quasi steady-state photoinduced absorption (PIA) and transient absorption (TA) spectroscopy in a broad visible and near-infrared spectral region on device-like structures, we gain insight into the mechanisms of charge generation and recombination. The results show that Li-TFSI, a commonly used additive, facilitates charge generation. As it turns out, reductive quenching, where hole transfer occurs prior to electron injection, plays a major role in charge generation for these dyes. However, we have evidence that initially separated charges are attracted back to the interface, likely due to the low dielectric constants, leading to increased recombination. This would be a major drawback of sDSCs. We suggest that to overcome this problem within the existing device configuration, exciton quenching must lead to a charge pair that is further spatially separated.