Low-Frequency Noise Investigation of Organic Field-Effect Transistors Based on N-Type Donor-Acceptor Conjugated Copolymer

Organic field-effect transistors (OFETs) based on n-type donor-acceptor (D-A) conjugated copolymer are at the forefront of research in organic electronics. Yet, an understanding of the fundamental aspects of their charge transport, in particular the relevant traps, remains limited. In this study, we show that the low-frequency noise (LFN) of n-type OFETs based on N2200 exhibits 1/<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> behavior. The normalized power spectrum density of the drain current (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>D</roman></sub>), namely (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>Id</roman></sub>/<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>D</roman></sub><sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sup>), varies similarly as (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>m</roman></sub>/<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>D</roman></sub>)<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sup> with gm being the transconductance, indicating the carrier number fluctuations. Examination on the annealing temperature and air stability of the devices with different contacts using LFN reveal sizably varied trap density, conforming the correlation between performance degradation and defect states. Thus, LFN provides quantitative insight into the charge transport behind.