Application of metal oxide microstructures in organic photovoltaics

• Main Author: Nirmal, Amoolya
• Other Authors: Hilmi Volkan Demir
• Format: Theses and Dissertations
• Language: English
• Published: 2016
• Subjects: DRNTU::Engineering::Electrical and electronic engineering::Optics, optoelectronics, photonics
• Online Access: https://hdl.handle.net/10356/69412
• Institution: Nanyang Technological University

With the emerging issues of climate change and depleting fossil fuel energy, solar cells are gaining widespread interest in both research labs and in the industry. Most of today's commercially available solar cells however are based on inorganic materials, mainly silicon. Organic PhotoVoltaics (OPVs), though lagging behind its inorganic counterpart in efficiency, has the potential for low cost, ease of fabrication and compatibility with flexible substrates to its advantage. In this thesis, the application of microstructures on the zinc oxide (ZnO) which form the electron selective inter-layers in inverted OPVs to enhance performance was investigated. Porous zinc oxide (ZnO) was demonstrated to serve as a microstructured electron selective layer enhancing light scattering in inverted organic photovoltaics. The use of porous ZnO structure led to a marked improvement in device performance when compared to non-porous ZnO, with 35% increase in current density and 30% increase in efficiency. The use of porous structure was extended to doped zinc oxide electron selective layers, namely indium-doped and aluminium dopes zinc oxide layers. The enhanced performance of OPV employing porous structure was observed for these devices also by virtue of the efficient light scattering property of the porous layer. Thus porous microstructure on metal oxide proved to be a portable efficient method of power conversion efficiency enhancement. Finally, photonic crystal was employed on the zinc oxide electron selective layer of inverted OPVs. By optimizing various process parameters, efficiency enhancement was observed for OPV devices with photonic crystal ZnO layer compared to planar ZnO electron selective layer. The highly ordered periodic structures of the photonic crystals provided effective light trapping which resulted in increased absorption in the active layer and subsequent current density improvement.