Download or read book Micro Solar Cells, Raman Spectroscopy, and Flow Synthesis of Copper Indium Selenide Nanocrystals written by Douglas Ryan Pernik and published by . This book was released on 2016 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt: Copper indium selenide nanocrystals are an attractive material for solar cell applications due to its favorable bandgap, moderate temperature synthesis, and solution processability in air. Solution processing in particular allows a whole range of new photovoltaic applications to be explored, as most current commercial solar cell technologies (bulk Si, CdTe, and CuIn [subscript 1-x] Ga [subscript x] Se2) employ high temperatures and/or high vacuums to grow quality crystals that make up the photovoltaic absorber layer. Copper indium selenide (CuInSe2) nanocrystals are unique in this regard in that they can be spray-deposited at room temperature in ambient conditions to form a solar cell’s light-absorbing layer. One particular application is investigated here: micro groove solar cells using flexible substrates. These solar cells are fabricated by filling micron-scale groove features with CuInSe2 nanocrystals. The CuInSe2 nanocrystals make contact with Au and CdS at opposite groove walls to create lateral junctions that allow charge extraction. Micro solar cells were optimized by varying the thicknesses of coatings, wall coating material thicknesses, groove angles, and ligand exchange procedures. Best-performing devices operate in the range of 3% power conversion efficiency utilizing this material set. Raman spectroscopy and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) were utilized to investigate the cationic ordering of CuInSe2 nanocrystals. In CuInSe2 nanocrystals, the Raman A1 mode appears as a broad peak centered at 182 cm−1, which is indicative of the sphalerite, cation-disordered structure. HAADF-STEM, on the other hand, revealed a partially ordered cationic structure in one particle, which is not typical for CuInSe2. Synthesizing the nanocrystals at higher temperatures and annealing at high temperatures both promoted cation ordering to the chalcopyrite structure. Finally, a flow-through reactor was designed to allow the controlled scale-up synthesis of CuInSe2 nanocrystals. This reactor utilized coiled glass tubing inside of a bulk heating element and was used to synthesize phase-pure nanocrystals.