Microscale Concentrated Photovoltaics and Soft Matter Lasers
Open Access
- Author:
- Grede, Alex
- Graduate Program:
- Electrical Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- December 02, 2021
- Committee Members:
- Tom Jackson, Major Field Member
Xingjie Ni, Major Field Member
Noel Giebink, Chair & Dissertation Advisor
Vincent Crespi, Outside Unit & Field Member
Kultegin Aydin, Program Head/Chair - Keywords:
- photovoltaics
non-imaging optics
organic semiconductors
organic laser diodes - Abstract:
- This work is focused on developing a new paradigm for microscale concentrating photovoltiacs (micro-CPV) and exploring materials and methods to enable diode lasing based on soft organic and halide perovskite semiconductors. By scaling CPV down to the microscale, the mass of the concentration optics drops and allows for the efficiency enhancements and solar cell material reduction inherent to concentration to be utilized both on rooftops and in space applications. I showed the fundamental limits to planar tracking that would be applicable to rooftop solar, demonstrated a proof of concept outdoors, and developed the mechanical tracking approach for a full scale panel. While the economics of terrestrial solar power over the timescale of this thesis and the additional technical challenges still to solve revealed by this work made micro-CPV difficult to compete with silicon, it still shows promise for space applications. We demonstrated a proof of concept showing how a monolithic package of optics, cells, and interconnections using space-qualified materials. I developed the electrical interconnection scheme needed to scale to a full array. Given the potential for higher specific power and lower material cost, micro-CPV is a viable option to support the rapid growth of the commercial space industry. The other major thrust of this work was on lasing for organic and halide perovskite semiconductors, which potentially offer broadly tunable non-epitaxial laser diodes. With the goal of developing laser diodes, we achieved several benchmarks by demonstrating lasing in perovskites with metal distributed-feedback (DFB) gratings, and subsequently, demonstrating the first continuous wave lasing. As both are likely to operate in a different current regime than traditional lasers, I developed an analytic treatment for the ideal laser diode in the space charge limited current regime and analyzed the effects of known parasitics for organic materials (triplet and polaron absorption/quenching). These results have lead to construction of high speed <1 ns rise-time and <5 ns pulse-width) small area laser diode structures both with DFB and with ring-resonators reducing heat dissipation. At this speed a low cavity loss perovskite device should lase, and organic lasers should be broadly achievable in bipolar materials where triplet and polaron absorption is negligible.