Operational Stability and Charge Transport in Fullerene-Based Organic Solar Cells

Abstract:

Organic photovoltaic cells are approaching commercially-viable levels of performance for a variety of applications"”particularly those which make use of the unique transparency, flexibility, and ultra-thin form factor that organic solar cells can achieve. With state-of-the-art solar to electric power conversion efficiencies now exceeding 15%, operational stability of organic photovoltaics is perhaps their most significant remaining challenge, as the presence of a variety of intrinsic photochemical and morphological degradation modes have thus far limited device lifetimes to several years or months. Thermally-evaporable Buckminster fullerenes (C60 and C70), with their remarkable optical and semiconducting properties, have enabled many of the most efficient and reliable organic photovoltaic cells over the past 15 years and remain central to state-of-the-art devices today.

The first part of this thesis explores the reliability of fullerene-based organics solar cells by monitoring their performance while aging continuously under simulated solar illumination and accelerating their aging with elevated temperatures (>130C) and high intensity illumination from white light emitting diodes (37 suns) and concentrated sunlight (100 suns).

The second part of this thesis will focus on the discovery and exploration of extremely long-range electron diffusion currents in fullerene-based organic heterostructures.