Broadband light absorption enhancement in polymer photovoltaics using metal nanowall gratings as transparent electrodes

Zhuo Ye,Sumit Chaudhary,Ping Kuang,Kai-Ming Ho

doi:10.1364/oe.20.012213

Abstract

The authors investigate light absorption in organic solar cells in which indium tin oxide (ITO) is replaced by a new metallic architecture (grating) as a transparent electrode. Different from typical metal nanowire gratings, our gratings consist of metal nanowalls with nanoscale footprint and (sub)microscale height [Adv. Mater. 23, 2469 (2011)], thus ensuring high optical transmittance and electrical conductivity. Simulations reveal that a broadband and polarization-insensitive light absorption enhancement is achieved via two mechanisms, when such silver nanowall gratings are employed in P3HT:PCBM based solar cells. Overall absorption enhanced by ~23% compared to a reference cell with ITO electrode.

Highlights

Indium tin oxide (ITO) is one of the most widely used transparent electrodes for solar cells and light-emitting devices because of its electrical conductivity as well as optical transparency
In a recent work [4], we proposed a new architecture for transparent electrodes, which consists of high aspect-ratio metal nanowall gratings held by a polymer matrix
We show that our transparent electrode architecture reported in Ref. 4 matches and outperforms ITO in its transparency and conductivity, respectively, but can enhance light absorption in organic photovoltaic (OPV) active layers for both polarizations

Summary

Introduction

Indium tin oxide (ITO) is one of the most widely used transparent electrodes for solar cells and light-emitting devices because of its electrical conductivity as well as optical transparency. Such schemes either provide absorption enhancement in only one polarization [17], or provide no enhancement in either polarization [18] because a significant part of incoming light is blocked by the metal structures. We show that our transparent electrode architecture reported in Ref. 4 matches and outperforms ITO in its transparency and conductivity, respectively, but can enhance light absorption in OPV active layers (we investigate the canonical P3HT:PCBM system in this report) for both polarizations. A remarkable ten folds high peak light absorption enhancement at specific wavelengths and a ~23% broadband enhancement are expected using the design, when compared to an ordinary cell using a 150 nm thick ITO coated glass as the transparent electrode

Simulation results and discussions

Summary