Effects of Static and Repetitive Uniaxial Bending Strains on the Electrical Properties and Trap Characteristics of Flexible Low-Temperature Polysilicon Thin-Film Transistors

Abstract

Changes in the electrical properties and trap characteristics of flexible low-temperature polysilicon thin-film transistors (TFTs) under the application of uniaxial bending strains and during repetitive bending cycles were investigated. When the bending strain increased, the transfer curve showed a negative shift, the output current decreased, and the subthreshold slope increased. After the bending strains were removed, the electrical performance showed recovery behavior, but the device performance could not return fully to its original state. The devices were also subjected to repetitive bending cycles. The transfer curves showed a positive shift after <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{4}}$ </tex-math></inline-formula> bending cycles and the output current increased. Using the transient current method, it was established that the detrapping time constant of the traps decreased and the peak amplitudes increased as a result of both the bending strain and the bending cycles. However, while the trap activation energy was not changed by static bending, it did decrease after the repetitive bending cycles. Both the changes in the electrical properties and the time constant spectra confirm that the trap state density increased as a result of the bending processes. However, the different trapping behaviors contributed to different degradations in the device’s electrical properties.