Lowering the driving voltage and improving the luminance of blue fluorescent organic light-emitting devices by thermal annealing a hole injection layer of pentacene

Gao Jian^{1, 2, 3}, Yu Qian-Qian^{1, 2, 3}, Zhang Juan^{1, 2, 3}, Liu Yang^{1, 2, 3}, Jia Ruo-Fei^{1, 2, 3}, Han Jun^{1, 2, 3}, Wu Xiao-Ming^{1, 2, 3, †}, Hua Yu-Lin^{1, 2, 3, ‡}, Yin Shou-Gen^{1, 2, 3, §}

(color online) AFM images (1 μm×1 μm) of 5 nm pentacene thin films on ITO/glass: (a) before and (b)–(d) after annealing (100 °C, 120 °C, and 150 °C).