Instigating network structure in bulk heterojunction organic solar cells creating a unique approach in augmenting the optical absorption

Abstract

In this study, enhancement of device characteristics of poly (3-hexylthiophene): phenyl C61-butyric acid methyl ester (P3HT:PCBM) by changing active layer film morphology into network structure is elucidated. Electrospraying assisted hierarchical assembly of short fibrils provides network structure. Effects of electrospraying parameters such as solvent, polymer blend concentration, applied voltage, tip to collector distance, flow rate and deposition time are analyzed. Solvent and applied voltage is observed to be the major parameters governing the formation of network structure. The optimized conditions are used to investigate the optical and structural properties in the fabricated device. Reflectance studies showed improvement in light absorption due to increased surface area. Structural characterization studies indicate an increase in crystallinity as compared to spincoated samples. The optimized conditions for the electrospun network structures additionally interpenetrated by P3HT:PCBM solution by spin coating are used to fabricate bulk heterojunction device. Device characteristics showed an increase in short circuit current and thus increase in efficiency from 2.18% to 3.66%. There is a enhancement of 37.5% going from a maximum external quantum efficiency of 40%–55% for electrosprayed and spincoated devices. This work suggests that network morphology could be used to enhance the photovoltaic properties.