Improve the n-type performance in organic heterojunction transistors by controlling thickness of copper phthalocyanineJianlin Zhou, Xiaoqing Shen, Zhen Wang, Shengdong Hu, Wei Huang, Xinge Yu and Ping GanEur. Phys. J. Appl. Phys., 70 2 (2015) 20102DOI: https://doi.org/10.1051/epjap/2015150149