Enhanced power conversion efficiency in polymer solar cells with embedded silver nanoparticles using different capping agents

Abstract

This present paper aims at realizing enhanced power conversion efficiency (PCE) in polymer solar cells with silver nanoparticles (Ag NPs) using different capping agents. Ag NPs, produced by solution chemistry of polyol process and capped with oleylamine (OA), polyvinylpyrrolidone (PVP) and thiol terminated polystyrene (PS-SH), were embedded in the photoactive layer of poly 3-hexylthiophene:6,6-phenyl-C61 butyric acid methyl ester (P3HT:PCBM) bulk heterojunction polymer solar cells. With the presence of suitable capping agent that disturbs aggregation, the dispersion can be better in order of OA, PVP and PS-SH. At an optimized blend ratio 2.5 wt % with 40 nm sized Ag NPs capped with PS-SH, the PCE increased from 3.11 % to 3.49 %, which was measured by using an AM 1.5G solar simulator at 100Mw/cm2 light illumination intensity. This increase can be attributed to improved short circuit current (increased from 8.49 mA/cm2 to 9.29 mA/cm2) due to an enhanced absorption of the P3HT:PCBM film caused by scattering effect. The incident light can be scattered by the embedded well dispersive Ag NPs while passing through the photoactive layer, thereby increasing the optical path length of the incident light and leading to a bound electron-hole pair called an exciton. This is evidenced by an original approach based on extinction spectra by ultraviolet-visible spectrophotometer.