Structural stability of naphthyl end-capped oligothiophenes in organic field-effect transistors measured by grazing-incidence X-ray diffraction in operando

Abstract We report on microstructural durability of 5,5′-bis(naphth-2-yl)-2,2′-bithiophene (NaT2) in organic field-effect transistors (OFETs) in operando monitored by grazing-incidence X-ray diffraction (GIXRD). NaT2 maintains its monoclinic bulk motif in operating OFETs with a = 20.31 ± 0.06 A, b = 6.00 ± 0.01 A, c = 8.17 ± 0.04 A and β = 96 . 64 ± 0 . 74 ° . Crystallites appear as a mosaic of single crystals reaching through the whole 50 nm thick active layer. The lattice parameters variation ( ( 3.25 ± 0.04 ) × 10 − 4 cm 2 / Vs and an average threshold voltage of − 13.6 ± 0.2 V, both varying less than 4% for the remainder of the 10 h period. This demonstrates crystalline stability of NaT2 in operating OFETs.