1 23 Journal of Materials Science: Materials in Electronics ISSN 0957-4522 J Mater Sci: Mater Electron DOI 10.1007/s10854-018-9521-2 The effects of solvent treated PEDOT:PSS buffer layer in organic solar cells Mohammed Al-Hashimi, Burak Kadem, Yaqub Rahaq, Raheem G. Kadhim & Aseel Hassan