Dresden 2014 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 19: Poster Session 1 (joint session with BP)
CPP 19.18: Poster
Dienstag, 1. April 2014, 09:30–13:00, P1
Direct evidence of the CT-state in organic small molecule solar cells by electroluminescence measurements — •Theresa Linderl, Julia Kraus, Stefan Grob, and Wolfgang Brütting — Institut of Physics, University of Augsburg, 86135 Augsburg, Germany
The open-circuit voltage of organic solar cells is limited by the formation of a charge-transfer (CT) state at the donor-acceptor interface. Direct spectroscopic evidence of the CT-state of organic solar cells can be obtained from electroluminescence measurements.
For single layer devices the electroluminescence signal is expected to reflect the fluorescence spectra of the respective material, whereas in heterojunction devices charge carrier recombination can either occur on one of the constituents or from the CT-state. We compare spectroscopic signatures of planar and bulk heterojunction organic solar cells based on small molecules to the signal of single layer devices of the individual components.
For voltages just above the open-circuit voltage Voc an additional feature in the low energy part of the spectrum can be detected, that can not be attributed to any of the used materials. We interprete this additional feature as the transition from the interfacial CT-state to the ground state and relate its energy to the open-circuit voltage of solar cells.