S1 Supporting Information Wire-on-wire Growth of Fluorescent Organic Heterojunctions Jian Yao Zheng, †,§ Yongli Yan, †,§ Xiaopeng Wang, † Yong Sheng Zhao, *,† Jiaxing Huang, ‡ and Jiannian Yao *,† † Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China ‡ Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208-3108 §These authors contributed equally to this work E-mail: yszhao@iccas.ac.cn; jnyao@iccas.ac.cn