Effect of Drying Time for the Qualitative Active Layer of an Organic Photovoltaic Device

Abstract

We investigated the effect of the drying time on the active layer based on a regioregular poly(3-hexylthiophene) (RR-P3HT):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM), as well as theperformance of polymer-based organic photovoltaic (OPV) devices. The devices were fabricatedwith different combinations of spin speed and solution concentration at a fixed thickness of theactive layer. These conditions varied the properties of the active layer in terms of the polymer crystallinityand the phase separation in the blend. We identified distinct differences for different dryingtimes of the solvent during the spin-coating process. The active layers were characterized by usinganalysis methods such as X-ray diffraction (XRD), ultraviolet-visible (UV-visible) spectroscopy andatomic force microscopy (AFM). The qualitative property of the active layer and the highest powerconversion efficiency were obtained with the slowest coated active layer with the lowest solutionconcentration under AM 1.5 G spectral illumination of 100 mW/cm2. PACS numbers: 41.20.-q, 02.20.Bb, 71.20.Rv, 72.15.CzKeywords: Bulk heterojunction, Polymer solar cells, P3HT:PCBM, Solution concen