Nonlinear Impedance Spectroscopy of Organic Hole-Only Solar Cell Devices
Rice, Robin
Rice, Robin
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Abstract
Organic Semiconductors (OSC) as used in Organic Solar Cells and Organic Light Emitting Diodes have garnered significant focus in the last decade as cheap, flexible, tunable alternatives to their Inorganic counterparts. However, while the crystalline electrical processes of Inorganic devices are well studied, Organic devices tend to be molecular in structure and thereby their electrical properties differ in function from more conventional Inorganic devices. One limitation in probing the electrical process of molecular OSCs is that of Electrochemical Impedance Spectroscopy (EIS) which relates a sourced AC voltage perturbation to its respective current output. Under small forward bias EIS reveals a linear dependence of current on source voltage. However, at higher forward bias, current techniques ignore higher order terms to approximate first order linear responses. This simplification overlooks valuable insights into material processes such as Space Charge Limited Current (SCLC), trapping, and electron-hole recombination limited current. Through Fourier analysis of the resultant current, Nonlinear Impedance Spectroscopy (NLIS) provides insight into said current limiting processes which are used to elucidate material properties such as the diode ideality factor and charge carrier mobility. Such constants are invaluable to the effective understanding and design of today’s Organic devices, ergo NLIS fills a critical niche in OSC analysis.
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Graduate
Graduate
Date
2020-01-01