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Ashlea Patterson

Ashlea Patterson lab photo


Materials Science and Engineering


University of Utah


Kelly Peterson

Faculty Sponsor(s): 

Michael Chabinyc

Faculty Sponsor's Department(s): 


Project Title: 

Charge Transport and Dopant Distribution in a Disordered Organic Semiconductor

Project Description: 

Organic semiconductors are materials of growing importance, as their low cost and ease of processing show promise for affordable, flexible electronic devices. However, charge transport in different organic thin film morphologies is not well understood, and accurate models are still in development. One variable affecting charge transport is dopant distribution within the film. Organic semiconductors must generally be doped to become conducting, and dopant distribution and concentration affect properties such as conductivity and thermopower. To better understand these effects in disordered organic materials, we investigated conductivity and thermopower in amorphous films of the common semiconductor Spiro-OMeTAD with varying distributions of dopant. Films were first spun-cast, then doped with F4TCNQ vapor over differing time intervals. Vapor doping has been shown to result in higher dopant concentrations at the film surface, and annealing can diffuse these dopants into the bulk film. Conductivity and thermopower were measured before and after annealing, and carrier concentrations estimated via UV-Vis spectrophotometry. With our results, we hope to better understand how diffusing dopants changes charge transport in disordered films, and gain a clearer picture of charge transport in organic semiconductors.