Optical method for calculating the dopant concentration of doped amorphous semiconductors Zhenfei Li, Liping Zhang, Wenzhu Liu, Youlin Yu, Shenglei Huang, Xiaodong Li, Yuhao Yang, Kai Jiang, Fanying Meng and Zhengxin Liu Eur. Phys. J. Plus, 137 7 (2022) 862 Published online: 26 July 2022 DOI: 10.1140/epjp/s13360-022-03027-5