Zimmerman Lab

Group Photo

Welcome to the Zimmerman group webpage! We primarily study thin film materials, often focusing on the optoelectronic properties of materials for energy applications. Several of our primary research areas are described below. Please contact us for more information or check out some of our papers.

Analysis of small-molecule based electronics

Shining OLED

Small-molecule based organic materials are used in a number of devices including organic light emitting diodes (OLEDs) and certain photovoltaic devices. The active layers of many of these organic electronic devices are fabricated from mixtures of different molecules. The amount of phase segregation, domain size, and phase purity are critical to device operation. We have a major effort to improve our understanding of the degree of phase separation, why materials phase separate, and the effects of segregation on properties. This research makes use of our vacuum thermal evaporation system, the atom probe tomography tool, and a variety of other materials quality and device efficiency characterization tools.

Compound semiconductors on silicon for tandem photovoltaics

Silicon photovoltaics are hard to beat: they are efficient, stable, and inexpensive, making the barrier to entry for other materials systems very high. In collaborations with NREL, we are investigating ways to create tandem photovoltaics using silicon as the infrared absorbing cell and III-V materials as the visible-light absorbing cell. While III-V materials hold the current photovoltaic efficiency records, they are generally very defect sensitive and are typically lattice- and symmetry-mismatched with silicon; therefore, our efforts are focused on reducing defects caused by lattice mismatch through selective area growth and modifying the silicon surface to eliminate symmetry-related anti-phase domains. This research uses inexpensive lithography techniques, metal-organic chemical vapor deposition, and a variety of materials analysis techniques.