Schmidtke Johanna P, Friend Richard H, Silva Carlos
Cavendish Laboratory, University of Cambridge, J.J. Thompson Avenue, Cambridge, United Kingdom.
Phys Rev Lett. 2008 Apr 18;100(15):157401. doi: 10.1103/PhysRevLett.100.157401. Epub 2008 Apr 14.
We present photoluminescence spectroscopy of blend thin films of poly(9,9-di-n-octylfluorene-alt-benzothiadiazole) (F8BT) with electron-donating copolymers under hydrostatic pressure. The photoluminescence spectrum of F8BT redshifts by 530+/-60 meV over pressures of 0.1 MPa-8.8 GPa. That of the interfacial charge-transfer exciton redshifts by 270-370 meV over a similar pressure range. Despite the relatively small shift of the charge-transfer exciton, the excited state dynamics at the molecular heterojunction are strongly enhanced due to the decreasing intermolecular distance, leading to favored exciplex emission.
