Air‐ and Active Hydrogen‐Induced Electron Trapping and Operational Instability in n‐Type Polymer Field‐Effect Transistors

Abstract

Organic field‐effect transistors (OFETs) have attracted much attention for the next‐generation electronics. Despite of the rapid developments of OFETs, operational stability is a big challenge for their commercial applications. Moreover, the actual mechanism behind the degradation of electron transport is still poorly understood. Here, the electrical characteristics of poly{[N,N‐9‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,59‐(2,29‐bithiophene)} (P(NDI2OD‐T2)) thin‐film transistors (TFTs) as a function of semiconductor/dielectric interfacial property and environment are systematically investigated, in particular, how the copresence of water, oxygen, and active hydrogen on the surface of dielectric leads to a sharp drop‐off in threshold voltage. Evidence is found that an acid–base neutralization reaction occurring at the interface, as a combined effect of the chemical instability of dielectrics and the electrochemical instability of organic semiconductors, contributes to the significant electron trapping on the interface of P(NDI2OD‐T2) TFTs. Two strategies, increasing the intrinsic electrochemical stability of semiconductor and decreasing the chemical reactivity of gate dielectric, are demonstrated to effectively suppress the reaction and thus improve the operational stability of n‐type OFETs. The results provide an alternative degradation pathway to better understand the charge transport instability in n‐type OFETs, which is advantageous to construct high‐performance OFETs with long‐term stability.

C3N5: A Low Bandgap Semiconductor Containing an Azo-Linked Carbon Nitride Framework for Photocatalytic, Photovoltaic and Adsorbent Applications

“…The last few decades have witnessed the rise of semiconducting, all-organic polymers as excellent metal-free and visible light-active materials for various optoelectronic and energy harvesting applications . Although impressive improvements in performance have been achieved, particularly for plastic solar cells, the synthesis procedures for semiconducting polymers are cumbersome and difficult to scale up, and the organic semiconductors themselves are unstable under the action of heat, light and/or ambient air . Consequently, there are scalability concerns related to semiconducting polymers, and requirement of heavy encapsulation to achieve even modest durability in the photovoltaic application.…”

Electronic Doping and Enhancement of n‐Channel Polycrystalline OFET Performance through Gate Oxide Modifications with Aminosilanes

“…[ 22,26 ] The density of water trap states in the channel—a common cause of mobility reduction [ 27 ] and operating voltage increase [ 28 ] —is also reduced due to the increased surface hydrophobicity. [ 29 ] Accordingly, transistors fabricated on ODTS‐treated gate oxide usually show higher carrier mobility than on bare gate oxide. For example, pentacene FETs fabricated on ODTS‐treated gate oxides resulted in a field‐effect mobility of 1.5 cm 2 V −1 s −1 , while bare gate oxide devices showed field‐effect mobilities of 0.7 cm 2 V −1 s −1 .…”

Charge‐Trapping‐Induced Non‐Ideal Behaviors in Organic Field‐Effect Transistors

“…In a full FET, we observed that the trapping mainly occurs near the source contact (Figure S10, Supporting Information), suggesting that the trapped charges mainly come from the source electrode. This impact is not due to the degradation, and the chemical and electrochemical instability of semiconductor that directly trapping the mobile carriers (Figure S11, Supporting Information) …”