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, §}

SEM images showing the morphology of the pentacene films: (a) without annealing sample, (b) 100 °C annealed sample, (c) 120 °C annealed sample, (d) 150 °C annealed sample.