Conjugated polymers have gained momentum as serious contenders for next-generation flexible electronics, but their susceptibility to water represents a major problem. Atmospheric water is ubiquitous and its inadvertent diffusion into polymeric devices generates charge carrier traps, reducing their performance and stability. A good understanding of the physical processes associated with the presence of water is therefore necessary in order to be able to suppress the related trapping events and enable stable, high-performance devices. Here, evidence is shown that water introduces traps in the bandgap of organic semiconductors and the impact of these traps on the electrical properties of polymer organic field-effect transistors (OFETs) based on indacenodithiophene-co-benzothiadiazole (IDT-BT) is investigated. Monitoring device parameters and the trap density of states (t-DOS) during moisture extrication reveals the existence of two types of water-related traps: shallow traps originating from water inhabiting the voids of the polymer film and deeper traps arising from chemisorbed water present at the dielectric/polymer interface. A trap passivation method based on flame-annealing is introduced to eliminate the interfacial traps. As a result, stable OFETs, with threshold voltage shifts less than ΔVth = −0.3 V and constant mobilities (
Bibliographical noteKAUST Repository Item: Exported on 2021-06-28
Acknowledged KAUST grant number(s): OSR -4106 CPF2019, OSR-2015-CRG4-2572, OSR-2018-CARF/CCF-3079
Acknowledgements: The work at Wake Forest University was supported by the National Science Foundation through Grants No. DMR-1627925 and ECCS-1810273. I.M. acknowledges funding from KAUST Office of Sponsored Research (OSR) under awards no. OSR-2018-CARF/CCF-3079, no. OSR-2015-CRG4-2572 and OSR -4106 CPF2019, as well as EC FP7 Project SC2 (610115), EC H2020 (643791), and EPSRC EP/M005143/1.