Presentation Title

Nonlinear Impedance Spectroscopy of Organic Hole-Only Solar Cell Devices

Presenter's Name(s)

Robin Rice, UVMFollow

Project Collaborators

Matthew White

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.

Primary Faculty Mentor Name

Matthew White

Status

Graduate

Student College

Graduate College

Program/Major

Materials Science

Primary Research Category

Engineering & Physical Sciences

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Nonlinear Impedance Spectroscopy of Organic Hole-Only Solar Cell Devices

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.