title: Influence of crystallinity and energetics on charge separation in polymer-inorganic nanocomposite films for solar cells.
abstract: The dissociation of photogenerated excitons and the subsequent spatial separation of the charges are of crucial importance to the design of efficient donor-acceptor heterojunction solar cells. While huge progress has been made in understanding charge generation at all-organic junctions, the process in hybrid organic:inorganic systems has barely been addressed. Here, we explore the influence of energetic driving force and local crystallinity on the efficiency of charge pair generation at hybrid organic:inorganic semiconductor heterojunctions. We use x-ray diffraction, photoluminescence quenching, transient absorption spectroscopy, photovoltaic device and electroluminescence measurements to demonstrate that the dissociation of photogenerated polaron pairs at hybrid heterojunctions is assisted by the presence of crystalline electron acceptor domains. We propose that such domains encourage delocalization of the geminate pair state. The present findings suggest that the requirement for a large driving energy for charge separation is relaxed when a more crystalline electron acceptor is used.
authors.affiliation: Centre for Plastic Electronics and Department of Chemistry, Imperial College London, South Kensington Campus, Exhibition Road, SW7 2AZ, U.K.
authors.forename: Neha
authors.initials: N
authors.lastname: Bansal
authors.forename: Luke X
authors.initials: LX
authors.lastname: Reynolds
authors.forename: Andrew
authors.initials: A
authors.lastname: MacLachlan
authors.forename: Thierry
authors.initials: T
authors.lastname: Lutz
authors.forename: Raja Shahid
authors.initials: RS
authors.lastname: Ashraf
authors.forename: Weimin
authors.initials: W
authors.lastname: Zhang
authors.forename: Christian B
authors.initials: CB
authors.lastname: Nielsen
authors.forename: Iain
authors.initials: I
authors.lastname: McCulloch
authors.forename: Dylan G
authors.initials: DG
authors.lastname: Rebois
authors.forename: Thomas
authors.initials: T
authors.lastname: Kirchartz
authors.forename: Michael S
authors.initials: MS
authors.lastname: Hill
authors.forename: Kieran C
authors.initials: KC
authors.lastname: Molloy
authors.forename: Jenny
authors.initials: J
authors.lastname: Nelson
authors.forename: Saif A
authors.initials: SA
authors.lastname: Haque