Tailoring optical transmittance of polyvinyl alcohol by FeCl3-doping for photovoltaic application Adly H. El-Sayed, Y. Hossien and Mahmoud A. Hamad Eur. Phys. J. Plus, 134 8 (2019) 415 Published online: 30 August 2019 DOI: 10.1140/epjp/i2019-12793-8