Study of the transport mechanism in molecular self-assembling devices

This paper focuses on the intrinsic charge transport in self-assembled monolayers (SAMs) and on the nature of transport in organic systems, in which surface and bulk properties are undistinguishable due to scale of consistent materials. Developed SAM-OFETs and photovoltaic (SAM-PVC) devices are characterized independently to study a role of charge delocalization both in electrical and optical manifold. The dynamics of charge transport are determined and used to clarify a transport mechanism. Taken together, these SAM devices provide a unique tool to study the fundamentals of polaronic transport on organic surfaces and to discuss the SAM-OFET and SAM PVC performance. Vapor phase molecular self-assembly of 1, 4, 5, 8-naphthalene-tetracarboxylic diphenylimide (NTCDI) having a rich π-stacking charge delivery system is used to enhance the performance of SAM-OFET and SAM PVC devices. Charge mobility in SAM-OFET could achieve values of more than 30 cm² V⁻¹ s⁻¹. The dynamics of charge transport in NTCDI-derived SAM-OFETs were probed using time-resolved measurements in an NTCDI-derived photovoltaic cell device. Time-resolved photovoltaic studies allow us to separate the charge annihilation kinetics in the conductive NTCDI channel from the overall charge kinetic in a SAM-OFET device. It has been demonstrated that tuning of the type of conductivity in NTCDI SAM-OFET devices is possible by changing Si substrate doping. In addition, the possibility of measuring transport in highly ordered SAM structures shines light on the polaron charge transfer in organic materials. Our study proposes that a cation-radical exchange (redox) mechanism is the major transport mechanism in SAM nanodevices. The role and contribution of the transport through delocalized states of redox active surface molecular aggregates of NTCDI are exposed and investigated in this report.     

Inkjet Printing of Organic Light-Emitting Diodes Based on Alcohol-Soluble Polyfluorenes

Russian Physics Journal - Ink compositions for inkjet printing based on poly(9.9-dioctylfluorene) and its alcohol-soluble analog are created. Current–voltage, brightness–voltage, and...