Abstract
Polymer solar cells (PSCs) have drawn increasing attention due to outstanding properties such as low production cost, light weight, low temperature fabrication and mechanical flexibility. However, the main limitation for the efficiency improvement of PSCs is the low photon absorption by the thin active layer. The optimal thickness of active layer is limited to the range of 50-100 nm due to low carrier mobility and short exciton diffusion length, which leads to poor light absorption.
Metal nanoparticles (NPs) such as gold (Au) and silver (Ag) NPs are investigated to study the localized surface plasmon resonance (LSPR) effect that can improve the light absorption and increase light scattering for PSCs. LSPR occurs when the oscillation of electronic clouds resonate with the incident light to cause more light absorption in the visible region. In addition, the incident light can be scattered by the metal NPs resulting in a longer propagation path.
In this study, Au NPs are incorporated with bulk heterojunction polymer solar cells (BHJ-PSCs). In order to investigate the LSPR effect on the device performance, Au NPs NPs are doped into poly-(3, 4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT: PSS) layer. The BHJ-PSCs are based on low band gap polymer thieno [3, 4-b]-thiophene/benzodithiophene and [6, 6]-phenyl C71-butyric acid methyl ester (PTB7: PC71BM). PSCs with Au NPs exhibit an improvement in the power conversion efficiency (PCE) when compared to the reference devices.