Effect of short chain iodoalkane solvent additives on photovoltaic performance of poly(3-hexylthiophene) and phenyl-C61-butyric acid methyl ester based bulk heterojunction solar cells

In this work the effect of short chain iodoalkane solvent additives such as iodobutane, iodoethane, diiodomethane and iodomethane on the photovoltaic parameters of poly(3-hexylthiophene) (P3HT) and phenyl-C-61-butyric acid methyl ester (PCBM) (1:1) based bulk heterojunction (BHJ) solar cells was studied in an ambient air conditions. Devices processed in 2% (v/v) of diiodomethane, iodobutane and iodoethane showed improved power conversion efficiency (PCE) of 2.40, 2.29 and 2.04%, respectively as compared to the efficiency of pristine (without additive) devices (1.93%), while devices made using iodomethane exhibit PCE of 1.66%. The UV-vis absorption spectra of devices showed that the presence of these additives results the growth of enhanced local structure with improved crystalline and order of P3HT domain. Furthermore, UV-vis absorption response of the solar cells before and after soaked in the aforementioned solvents indicates that each additive has selective solubility for PCBM except iodomethane in which both P3HT and PCBM showed solubility. (C) 2015 Elsevier B.V. All rights reserved.