| 초록 |
We used polymer gate-dielectric (PGD) with different molecular weights (MW) to investigate the effect of chain-end density of PGD, i.e., the number of chain-end per unit volume, on the bias stress stability of organic field-effect transistors (OFETs). Under bias stress in ambient air, OFET drain current decay and threshold voltage shift increased as the MW of the PGD decreased (MW effect). The frequency prefactor ω has an important influence on this MW effect; this influence confirms that the MW effect is caused by the density of polymer chain-ends that form trap sites during bias stress. Free volume at polymer chain-ends is large enough to allow the residence of water molecules, the presence of which significantly increases the number of charge-trap sites. In contrast, polymer chain-ends without water molecules do not allow charge trapping and thus bias stress stability was independent of MW when measurement was performed under vacuum. |
