resumo
A large photoresponse is observed at the interface between a highly ordered rubrene single-crystal and an amorphous fullerene film, with responsivity values 300 times higher than the corresponding bulk-heterojunctions and an isolated single-crystal. The rubrene-PCBM interface displays a wide range photoresponse, particularly enhanced in the red part of the visible spectrum presenting an exceptionally high photogeneration yield for lower excitation energies. Increased dark conductivity and electronic structure calculations indicate a polarization effect that reduces the band-gap and assists interfacial exciton separation to donor and acceptor layers well apart, minimizing electron-hole recombination. Wavelengthdependent photoconductivity and thickness-dependent absorption measurements, supported by computational analysis, show that primary excitons formed in rubrene and PCBM evolve to excitons which are effectively separated at the interface. Our results provide important insights into harnessing excitons generated in both the electron donor and acceptor materials increasing the efficiency in organic devices.
palavras-chave
CHARGE-TRANSFER INTERFACES; SOLAR-CELLS; ORGANIC SEMICONDUCTORS; EXCITON DISSOCIATION; QUANTUM EFFICIENCY; ELECTRON-ACCEPTOR; TRANSISTORS; POLYMER; PERFORMANCE; MOLECULES
categoria
Materials Science; Physics
autores
Pinto, RM; Macoas, EMS; Alves, H
nossos autores
Helena Alves
Investigador Principalagradecimentos
The authors thank V. Soares for technical support. The authors acknowledge the Advanced Computing Laboratory at the University of Coimbra for providing computing resources. FCT Fundacao para a Ciencia e Tecnologia (Portugal) supported this work through financially funding the Associated Laboratory Institute of Nanoscience and Nanotechnology, project Pest-OE/CTM/LA0024/2011 and grant nr. SFRH/BPD/84820/2012.