Event
Ph.D. Dissertation Defense: Wei-Lun Hsu
Friday, July 28, 2023
10:00 a.m.
AVW 1146
Maria Hoo
301 405 3681
mch@umd.edu
ANNOUNCEMENT: Ph.D. Dissertation Defense
Name: Wei-Lun Hsu
Committee:
Professor Mario Dagenais, Chair/Advisor
Professor Martin Peckerar
Professor Yanne Chembo
Professor Avik Dutt
Professor Sylvain Veilleux, Dean's Representative
Date/time/Location: Friday, July 28, 2023 at 10 am
Location: AVW 1146
Title: Perovskite, Perovskite/CIS Solar Cell and Si3O4/SiO2 Arrayed Waveguide Gratings
Abstract:
(1)Perocskite Solar Cell and The Application to Tandem Solae Cell
A FAxMA(1-x)PbI3 perovskite solar cell with a tunable bandgap from 1.59 to 1.50 eV is proposed. A superstrate configuration with an inverted planar structure is adopted. The structure of our FAxMA(1-x)PbI3 perovskite solar cell is FTO glass/PTAA with m-MTDATA/Perovskite/PCBM/Ag. Sequential PTAA doping and solvent-assisted annealing techniques are used to improve the performance of FAxMA(1-x)PbI3 perovskite solar cell.
SEM images clearly show that MAPbI3 (x=0) film has the highest degree of crystallinity with an average grain size over 2 m. As the FAI proportion increases, the degree of crystallinity decreases, resulting in smaller grain size. FA0.33MA0.67PbI3 perovskite material is the optimized ratio for single-junction solar cell and the corresponding power conversion efficiency (PCE) is 16.5%, with an open circuit voltage (Voc) of 1.02 V and a short-circuit current (Jsc) of 24.5 mA/cm2. A fill factor (FF) of 66% is extracted and it reflects a lower crystallinity. The external quantum efficiency (EQE) of FA0.33MA0.67PbI3 perovskite solar cell is measured to be above 90% of efficiency over a broad spectral range from 400 to over 600 nm and remains above 80% around 760 nm, and the absorption onset is pushed to 820 nm due to a lower optical bandgap of 1.54 eV.
MAPbI3 solar cell with optical bandgap of 1.59 eV is a great fit as the top cell paired with CIS bottom cell with bandgap of 1 eV. A four-terminal perovskite-CIS tandem solar cell is proposed. I-V characteristics and EQE are taken to investigate the performance. The champion cell demonstrates a PCE of 19.5% which improves the optimized single-junction FA0.33MA0.67PbI3 perovskite solar cell by 3%. If a freshly fabricated bottom CIS solar cell was used for tandem solar cell, the overall PCE would be expected to be above 20%.
(2)Arrayed Waveguide Gratings
Our AWG design and devices are based on 100-nm Si3N4 on SiO2 platform. V-shaped and crossover structure have been discussed. V-shaped structure is based on the structure used in Rsoft while the crossover structure overlaps two FSRs and shorten the lengths of arrayed waveguides.
For the lower resolving power design, the peak transmission can reach -1.9 dB and the highest resolving power is around 5,300. For the higher resolving power design, the peak transmission is -2.0 dB and the maximin resolving power goes above 18,000. The side lobes are prominent due to larger phase error. The performance from all three input channels is very consistent.
Cascaded AWG is developed to broaden the FSR without increasing the footprint. The design approach used in the project is a small primary AWG with broad FSR and a bunch of large secondary AWG. However, it requires flat response to prevent large loss at outer channels as well as the channel cross-points.
The design of flat-top primary AWG is based on modifying the power profile at input aperture and the phase distribution at output aperture, creating an input signal into output FPR to be a sinc function.
The V-shaped structure is adopted when designing flat-top primary AWG. Due to the altered geometry of tapers along the input aperture, additional phase difference needs to be compensated.
TSP AWG is used as secondary AWG for better cross-dispersion optics setup. One-top-hat or two-top-hat layout is utilized in the design. Experimental results demonstrates that Rowland primary AWG has higher peak transmission but suffer significant loss at channel cross-points while flat-top primary AWG features slightly lower peak transmission but has huge improvement at channel cross-points for more than 12 dB experimentally. However, phase error generates prominent side lobes and deteriorates the crosstalk. Cascaded AWG with flat-top primary stage shows flat output profile within the passband, but performs poorly in filtering out unwanted signals outside passband. Rowland primary AWG performs well in filtering out noise.
