Small gap semiconducting organic charge-transfer interfaces

Abstract

We investigated transport properties of organic heterointerfaces formed by single-crystals of two organic donor-acceptor molecules, tetramethyltetraselenafulvalene and 7,7,8,8-tetracyanoquinodimethane (TCNQ). Whereas the individual crystals have unmeasurably high resistance, the interface exhibits a resistivity of few tens of megohm with a temperature dependence characteristic of a small gap semiconductor. We analyze the transport properties based on a simple band diagram that naturally accounts for our observations in terms of charge transfer between two crystals. Together with the recently discovered tetrathiafulvalene–TCNQ interfaces, these results indicate that single-crystal organic heterostructures create functional electronic systems with properties relevant to both fundamental and applied fields

Surface doping in T6/PDI-8CN2 heterostructures investigated by transport and photoemission measurements

“…These results resemble those discussed in other recent reports [1,2,3,6,7,8], with the most remarkable example given by the insulator-to-metal transition demonstrated at the interface between Tetrathiofulvalene (TTF) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) single crystals [11] [12].…”

Photoconductive response in organic charge transfer interfaces with high quantum efficiency

“…This can be observed in recent examples of crystal on crystal lamination. Conjugating tetramethyltetraselenafulvalene and TCNQ crystals, for instance, forms a small-gap semiconductor system 34 , whereas in PDIF-CN 2 (N,N 0 -1H,1H-perfluorobutyl dicyanoperylenecarboxydiimide) and rubrene system the valence band of the electron donor (rubrene) and the conduction band of the electron acceptor (PDIF-CN 2 ) are practically aligned 35 . As a result, the interfacial electron density presents a linear dependence of the temperature.…”

“…The mechanism associated with the observed higher current density at the interface is probably related to band bending due to the electrostatic potential created by polarization effects that ultimately lead to charge transfer from the HOMO of rubrene to the LUMO of TCNQ (ref. 34). In addition, the hybridization of the interfacial molecules of TCNQ-rubrene is likely to be quite small, comparable to the weak coupling between molecular planes observed in the individual constituents.…”

Ambipolar transport and charge transfer at the interface between sexithiophene and N,N-bis(n-octyl)-dicyanoperylenediimide films

“…These results are in agreement with recent reports 1-3, 16 and with the remarkable example of insulator-to-metal transition demonstrated in the case of interfaces between tetrathiofulvalene (TTF) and 7,7,8,8tetracyanoquinodimethane (TCNQ) single crystals. 17,18 In this paper, we have studied the properties of high-quality sexithiophene (T6)/N,N-bis(n-octyl)-dicyanoperylenediimide (PDI-8CN 2 ) heterostructures composing the active channels of field-effect transistors. The choice of these organic semiconductors is related to the peculiar values of the molecular energy levels, which favor theoretically a transfer of electrons from the highest occupied molecular orbital (HOMO) level of the p-type semiconductor to the lowest unoccupied molecular orbital (LUMO) level of the n-type compound.…”