PERFORMANCE OPTIMIZATION OF INVERTED ORGANIC PHOTOVOLTAIC CELLS

Open Access
Author:
Farbo, James Michael
Area of Honors:
Chemical Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Enrique Daniel Gomez, Thesis Supervisor
  • Michael John Janik, Honors Advisor
Keywords:
  • organic photovoltaic
  • solar energy
  • renewable energy
  • bulk heterojunction
  • bilayer heterojunction
  • ordered heterojunction
  • P3HT
  • PFTBT
  • PCBM
Abstract:
Organic photovoltaics provide an alternative pathway to harness solar energy and reduce the world’s dependence on fossil fuels. While organic photovoltaics have shown promise on a laboratory scale, many aspects of their design that must be optimized before devices can be mass produced on an industrial scale. This thesis explored two unique families of organic photovoltaics that possess conventional and inverted geometries. Organic photovoltaics with conventional geometries direct electrons towards the top electrode (cathode), while holes travel towards the bottom electrode (anode). Contrarily, organic photovoltaics with inverted geometries have opposite polarity relative to conventional geometries, which flips the direction charges travel. In short, inverted organic photovoltaics have a few inherent benefits over conventional organic photovoltaics including relatively low oxidation of top electrode and reduced degradation of active layer materials, which promote long-term device performance and stability. Due to their high potential for commercial applications, inverted devices with both bulk and bilayer heterojunctions were the main subjects of our academic research. This thesis explored devices with Glass/ITO/ZnO/Active Layer/MoO3/Ag architecture – inverted bulk heterojunction devices contained a 1:2 P3HT/PFTBT active layer, whereas inverted bilayer heterojunction devices contained a P3HT layer directly on top of a PFTBT layer. The goal of this thesis was to successfully create inverted bulk heterojunction and inverted bilayer heterojunction photovoltaics and optimize one key component in their design – the electron blocking layer (MoO3). Varying the thickness of MoO3, while keeping all other design variables constant, allowed us to experimentally determine the optimal thickness to be 0.1 nm for both systems. Max efficiencies for inverted bulk heterojunction and inverted bilayer heterojunction devices possessing 0.1 nm MoO3 were 0.32% and 0.099%, respectively. These experimental findings can guide the optimization of related device systems, particularly those containing block-copolymer based heterojunctions, which promotes an incremental increase in organic photovoltaic device performance.