Optical Management Techniques for Organic Solar Cells

TL;DR

This thesis investigates optical management techniques for organic solar cells, demonstrating significant efficiency improvements through textured rear reflectors and optimized microlens array integration to enhance light trapping and absorption.

Contribution

It introduces novel fabrication methods for textured rear reflectors and explores direct MLA integration on transparent electrodes to improve light management in organic solar cells.

Findings

Up to 25% increase in power conversion efficiency with textured rear reflectors.

Approximately 15% enhancement in short-circuit current density using MLA directly on electrodes.

Effective light trapping techniques demonstrated for organic photovoltaic performance improvement.

Abstract

In this thesis, two different optical management techniques for organics based solar cells are explored. The first part is focused on the development of a textured rear reflector for OPVs. The use of textured reflector (TR) facilitates an increase in the optical path length along with light trapping within the active layer. TR was fabricated through a relatively simpler technique by depositing metal films over a microlens array (MLA). Zinc oxide nanoparticles were used to minimize the shadowing effect. Using TR, enhancements in short-circuit current density and power conversion efficiencies up to 10-25% were demonstrated for a polymer based organic solar cell. The second part is focused on improving the effectiveness of MLA incorporation in OPVs. The increase in path length achieved using MLA can be improved by increasing the refractive index of MLA and incorporating MLA directly on the transparent electrode instead of glass substrate. This approach could avoid the optical losses occurring at the interface between MLA and glass substrate and increase the net path length of light within the active layer. Initial experimental results are discussed to understand the potential of this approach. Approximately, ~15% enhancement in short-circuit current density was achieved by using MLA directly on the transparent electrode in ITO-free devices.