Dresden 2014 – scientific programme
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O: Fachverband Oberflächenphysik
O 22: Organic Electronics and Photovoltaics II (CPP jointly with DS, HL, O)
O 22.8: Talk
Monday, March 31, 2014, 17:15–17:30, ZEU 222
Correlating structural order and morphology with transport properties in donor-acceptor block copolymers for organic photovoltaics — •Gaurav Gupta1, Chetan Raj Singh2, Ruth Lohwasser3, Peter Muller Buschbaum4, Mukundan Thelekkat3, Harald Hoppe2, and Thomas-Thurn Albrecht1 — 1Martin-Luther-Universität Halle-Wittenberg,Germany — 2Technische Universität Ilmenau, Germany — 3University of Bayreuth,Germany — 4Technische Universität München,Germany
Microphase separated donor-acceptor block copolymers are promising systems for morphology control in OPV's. A nanostructure on exciton diffusion length scale, crystalline order and percolating pathways for charge transport are pre-requisites for obtaining good device properties. We here present a systematic study of the correlation between structure and charge transport in thin films of P3HT-b-PPerAcr after different thermal treatments. Combining AFM, microscopy and GISAXS we show that films annealed in the melt state above the melting temperatures of both components form typical microphase separated structures oriented parallel to the substrate, while films crystallized from the disordered state as obtained from spin coating show no well-defined microphase separated structures. GIWAXS measurements reveal that crystallization from the ordered state leads to strongly textured samples. Charge carrier mobilities as measured by SCLC were improved by 2 orders of magnitude in films crystallized from the disordered state, the unfavorable orientation of the microphase morphology in melt annealed films resulted in poor device performance.