Thin Film Electronics

The Thin Film Electronics Project is developing measurements on active thin film electronic devices like transistors which currently enable user interfaces (sensors, touch pads, displays) in large area and portable electronics and measurements on solar cells for green energy. These measurements help to enable the commercialization of technologies that address society’s current and future needs in Information and Communications, Security, Health Care/Medical Monitoring, and Energy.

Thin Film Electronics has greatly affected how humans interact with electronics and as a consequence improved the overall quality of life. Examples of macro electronics applications include active matrix liquid crystal displays and imaging sensors for digital radiography. A core building block for many thin film electronic applications is the thin film field-effect transistor, or simply thin film transistor (TFT), which serves as a pixel control element (switch) in display backplanes and sensor arrays, and as an active circuit element in applications requiring computation. Other thin film active electronic devices include light emitting diodes, sensor elements, and photovoltaic cells. To increase electronic functionality for broader applications, new thin film semiconductor materials, manufacturing methods, and computer aided design tools will be required. This project aims to establish the metrology needed to enable diverse macro electronic device technologies for a growing list of large-area electronic applications.

The Thin Film Electronics Project was established in 2005 as response to the potential economic significance of commercial electronics incorporating thin film active electronic materials and devices. Project researchers have focused on developing metrology and measurement methodology for TFTs based on solution processed organic semiconductors (polymeric and small-molecule). Studying the electronic properties of organic TFTs, researchers have shown the significant dependence of charge transport on the longitudinal electric field in the transistor channel (Poole-Frenkel-like effect) once parasitic contact effects are minimized, developed capacitance-voltage measurements and analysis methods for characterizing the electronic properties of the channel region and contacts for organic TFTs, and demonstrated correlations between molecular design, microstructure, and electronic properties for organic thin film and single crystal field-effect transistors.

Researchers have also begun evaluating organic based photovoltaic devices and related polymeric semiconductor materials as a viable macro electronics technology for providing low-cost renewable energy. Early emphasis has been placed on developing measurement methods to elucidate a fundamental understanding of photophysical and electronic processes in photovoltaic devices with complex thin film microstructure (phase segregated multi-component bulk heterojunction devices) to allow rapid and significant improvements in materials synthesis and device engineering and processing. 

Most recently, project researchers in collaboration with Penn State University began addressing the metrology needs to enable zinc oxide TFTs as a commercial macro electronics device technology. Zinc oxide TFTs may face a lower entry barrier to manufacturing than organic based devices given their compatibility with existing semiconductor processing methods, and they may provide significant improvements in electronic performance having a field-effect mobility in the range of 10 cm2/Vs to 100 cm2/Vs. Preliminary flicker noise studies performed by researchers of the Thin Film Electronics Project reveal zinc oxide TFTs to have a Hooge parameter (an empirical parameter relating to device stability) which is as good as, or better than, that reported for hydrogenated amorphous silicon TFTs.

• Demonstrated novel self-assembly process for fabricating self-patterned organic thin film transistors.
• Demonstrated correlation between molecular design, microstructure, and electronic properties for organic thin film
• Developed capacitance-voltage characterization technique for analyzing the contact and channel properties of thin film transistors.