Molecular Self-Assembly and Interfacial Engineering for Highly Efficient Organic Field Effect Transistors and Solar Cells

Abstract

Abstract : Versatile surface and interface tailoring has been realized through molecular monolayers, polymer nanolayers or peptide monolayers. Insulating and semiconducting molecular phosphonic acid (PA) self-assembled monolayers (SAMs) have been developed for applications in organic field-effect transistors (OFETs) for low-power, low-cost flexible electronics. Multifunctional SAMs on ultrathin metal oxides, such as hafnium oxide and aluminum oxide, are shown to enable (1) low-voltage (sub 2V) OFETs through dielectric and interface engineering on rigid and plastic substrates, (2) simultaneous one-component modification of source/drain and dielectric surfaces in bottom-contact OFETs, and (3) SAM-FETs based on molecular monolayer semiconductors. The combination of excellent dielectric and interfacial properties results in OFETs with low-subthreshold slopes down to 75 mV/dec, high I(on)/I(off) ratios of 10(5)- 10(7), contact resistance down to 700 Omega cm, charge carrier mobilities of 0.1-4.6 cm(2)/(V s), and general applicability to solution-processed and vacuum-deposited n-type and p-type organic and polymer semiconductors. (4) Polystyrene (PS) nanolayer as interface for OFETs, (5) threshold voltage control in OFETs with dielectric layer modified by the genetically engineered polypeptide (GEP) and (6) graphene oxide (GO) nanosheet-based OFETs and one diode-one resistor cell arrays for non-volatile memory have been also achieved. (7) Exquisite control of molecules is reached by monolayer assembly/confinement, and monitored by photon-STM for molecular motions, reactions and conductance in ground state and excited state.