Figure 5

(a) Optical bandgap Eop determined from the IOT spectra for thin rubrene film (deposited at Tsub = 108 °C) and for thick rubrene film (Tsub = 220 °C), respectively. The inset shows the practical definition of ΔEop. (b) Variation of Eop(T) for rubrene films deposited with various Tsub from 103 to 210 °C. The solid curves are the fitting results. (c) Fitting parameters of O’Donnell and Chen eq. for rubrene films fabricated with various Tsub = 146–210 °C.