Tuning interfacial charge-transfer excitons at polymer-polymer heterojunctions under hydrostatic pressure.
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.
Cavendish Laboratory, University of Cambridge, J.J. Thompson Avenue, Cambridge, United Kingdom. jpschmidtke@gmail.com
Johanna P
JP
Schmidtke
Richard H
RH
Friend
Carlos
C
Silva