Regensburg 2016 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 12: Photovoltaics (Joint session of HL and DF, organized by HL)
HL 12.4: Vortrag
Montag, 7. März 2016, 15:45–16:00, H2
Hybrid charge transfer excitons at ZnMgO/P3HT interfaces — •Moritz Eyer, Sergey Sadofev, Joachim Puls, and Sylke Blumstengel — Institut für Physik, Humboldt-Universität zu Berlin
The performance of hybrid photovoltaic devices is strongly related to the efficiency of the charge separation process. In photovoltaic operation excitons generated in the organic and inorganic part diffuse to the interface of the heterojunction. It is suggested that prior to full charge separation a hybrid charge transfer exciton (HCTE) is formed i.e. a coulombically bound charge pair residing on both sides of the interface. Only after dissociation of such a pair a photocurrent is generated.
The formation of HCTE is experimentally verified in planar ZnMgO/poly(3-hexylthiophene) (P3HT) heterojunction devices via electroluminescence (EL) measurements [1]. Radiative recombination across the interface produces EL in the near infrared spectral region. The energy offset Δ EIO between the conduction band minimum of ZnMgO and the P3HT highest unoccupied molecular orbital is tuned systematically by varying the Mg content. Combined analysis of radiative properties and the open circuit voltage VOC in photovoltaic operation shows a clear correlation to the HCTE transition energy.
Investigation of the properties of HCTE yields valuable input for the optimization of the charge separation process at inorganic/organic semiconductor interfaces in order to fully exploit the potential of hybrid devices.
[1] M. Eyer et al., Appl. Phys. Lett. 107, 221602 (2015).