Periodic Reporting for period 1 - FOCUS (Fluorescent Optical Concentration of Uncollimated Sunlight)
Reporting period: 2022-07-01 to 2024-12-31
The goal of focus is to design, fabricate and test a completely new approach to luminescent solar concentrators (LSCs) that solves the long-standing problem of low efficiency and low concentration limits exhibited by all current LSCs. The problem with all current designs is the unavoidable coupling between concentration ratio, area and efficiency: scaling to larger area (required to reach higher concentration ratio) always leads to substantial reductions in efficiency because emitted light must travel a much longer distance than incident sunlight. This long distance leads to unavoidable reabsorption and escape cones losses that leave practically achievable LSC efficiency values far below the thermodynamic limit. My approach fundamentally bypasses this problem by making absorption and emission occur along the same axis, matching the distance travelled by incident sunlight and emitted light. This is fundamentally possible by replacing concentration of emitted light with concentration of photogenerated carriers, followed by collimation of emitted light. The collimated emission then can be concentrated to values limited only by the diffusion length of photogenerated carriers and the divergence angle of the emission, allowing for designs that approach the thermodynamic limited concentration ratio (given by Stokes shift).
In this first phase of the project, one student has focused on the optical simulations for the design of the diffuse light concentrators. He succeeded in finding three different designs that reach simulated concentration values well above 100X, an order of magnitude better than state-of-the-art luminescent solar concentrators. He has also now fabricated these designs and is currently working together with other team members to test their performance. On the material side, one student and one postdoc have been mainly focused on making patterned single crystals of halide perovskites with various compositions, where the patterning control spans from nanoscale to microscale features and can be uniform over centimeter scale. They have now found two different routes to such compositional and shape control and are currently working on improving the uniformity on the macroscale. One postdoc and one student have also been working together on a prototype of a new type of instrument, an ultrafast 3D nanoprinter, that allows for printing and ultrafast measurements of halide perovskite emitters during photosynthesis. They have found that the laser parameters play a crucial role in the results and are exploring the fundamental mechanism behind the synthetic property control that is now available. This new type of prototype instrument has a unique combination of capabilities that is not available anywhere else in the world.
This new prototype microscope has inspired a new type of spectroscopy that is currently being patented. We think outside of the intended impacts in diffuse light concentration that were the main target of the proposed research, we can also develop a very valuable tool for in-line materials and device characterization based on light emission. We also see opportunities for optical computing and artificial intelligence are working with several partners to further explore these exciting unexpected developments.