Speaker
Ren Borgia
Speaker's Institution
Colorado State University
Date
2026-05-12
Time
4:00pm
Location
Yates 102/103
Mixer Time
3:45pm
Mixer Time
Chemistry B101E
Calendar (ICS) Event
Additional Information
Seminar Abstract:
Ternary copper chalcogenide semiconductors can offer promising optoelectronic properties, but their performance is often hampered by crystallographic defects that are difficult to identify with standard laboratory characterization. This seminar explores the relationship between synthetic pathways and atomic-scale disorder in two ternary copper selenide materials, Cu3PSe4 and Cu2SiSe3.
We first look at the structural evolution of the colloidal Cu-P-Se nanoparticle system using synchrotron X-ray diffraction and Pair Distribution Function (PDF) analysis of aliquots taken at intervals throughout the reaction. We explore the local environment of phosphorus en route to Cu3PSe4 nanoparticle formation by refining structural models against synchrotron data. Our analysis supports the hypothesis that phosphorus remains local by occupying Cu-sites as antisite defects within intermediate Cu-Se binary phases, which appears to facilitate the ultimate formation of the ternary Cu3PSe4 phase.
Continuing the investigation of synthesis routes and local structure in ternary copper selenide materials, this talk highlights also the challenges of synthesizing the bulk, zinc-blende-derived material, Cu2SiSe3, and its defects. This material is of particular interest due to its theoretically predicted “tolerance” to the deleterious antisite defects common in other zinc-blende-derived materials, such as CZTS and CIG(S,Se). To avoid the long reaction times, impurities, and other synthetic limitations imposed by traditional solid state and flux methods, we leverage thermodynamic driving forces using a gas-phase metathesis route for the successful synthesis of Cu2SiSe3. Additionally, we discuss our ongoing efforts using high-resolution structural modeling to determine if Cu2SiSe3 successfully resists antisite defect formation as predicted. Furthermore, we address the appearance of additional reflections in experimental powder X-ray diffraction (PXRD) patterns that, along with transmission electron microscopy (TEM) observations, suggest the presence of extended defects, such as stacking faults, under certain synthetic conditions but not others. Future work aims to investigate these hypothesized extended defects using stacking fault simulations, continued structural investigation via TEM, and electronic property measurements. By coupling the investigation of diverse synthetic methods with rigorous defect analysis, this work highlights the fundamental links between synthetic approaches and resulting atomic-scale structure of these photovoltaic materials.
