Ultrapure C60 field-effect transistors and the effects of oxygen exposure

Abstract

We report on electrical measurements of C60-based field-effect transistors (FETs) that were fabricated and characterized in an ultrahigh vacuum, and on how their properties are affected by progressive exposure to impurity gases. The in situ experiments demonstrated that oxygen-free devices have unipolar n-type characteristics with an electron field-effect mobility of up to 0.08cm2∕Vs immediately after fabrication, and up to 0.5cm2∕Vs after an annealing treatment in a high vacuum. Upon oxygen exposure, the effective electron mobility dramatically decreases in a way that depends on the diffusion time of oxygen into the C60 thin film. It is shown that contact with oxygen can lead to C60-FETs with ambipolar characteristics. The real-time measurement of the degradation of the devices subjected to oxygen allows us to derive the diffusion rate for oxygen molecules in C60 thin films, yielding a diffusion constant D=4×10−12cm2∕s.

Extended Lifetime of Organic Field‐Effect Transistors Encapsulated with Titanium Sub‐Oxide as an ‘Active’ Passivation/Barrier Layer

“…Thus, if these impurities are subsequently removed from the semiconductor material, the device performance can be recovered. Similar results have been reported for FETs fabricated with C 60 as the organic semiconductor; [20] I ds was demonstrated to recover when the oxygen was removed by thermal annealing in high vacuum. Therefore, the performance recovery after TiO x deposition indicates the active scavenging role of the TiO x layer.…”

Chemical changes in PCPDTBT:PCBM solar cells using XPS and TOF-SIMS and use of inverted device structure for improving lifetime performance

“…Other reports using XPS to study degradation included focusing on the fullerene derivative [8,9]. The studies showed that oxygen uptake increased during exposure and suggested that the PC61BM undergoes both temporary and permanent chemical reactions with oxygen.…”

Improvement of Stability for Small Molecule Organic Solar Cells by Suppressing the Trap Mediated Recombination

“…It has been reported that C 60 is very sensitive to oxygen and water, which would induce the decrease of carrier mobility and the traps for electrons in C 60 layer. 35,36 In the conventional OSCs, the C 60 is adjacent to the top metal cathode, suggesting that it is vulnerable to the air atmosphere. Thus, the quick increase of R S can be ascribed to the carrier mobility decrease of C 60 layer with increasing exposing time.…”