NM05.11.22 : Structural, Optical and Hole Transport Properties of Earth-Abundant Chalcopyrite (CuFeS2) Nanocrystals

5:00 PM–7:00 PM Apr 5, 2018 (America - Denver)

PCC North, 300 Level, Exhibit Hall C-E

Ebin Bastola1 Khagendra Bhandari1 Randy Ellingson1

1, University of Toledo, Toledo, Ohio, United States

Semiconductor nanocrystals (NCs) are promising materials for the fabrication of opto-electronic devices. The chalcopyrite NCs such as CuInS2 has been well explored, however, the properties of CuFeS2 NCs are not well studied. Here, we report a thiol-free colloidal synthesis, characterization, and application of earth-abundant chalcopyrite (CuFeS2) nanocrystals (NCs). The CuFeS2 NCs were synthesized using hot-injection colloidal method, and are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Raman and UV-Vis-NIR spectroscopy. The synthesized CuFeS2 NCs have tetragonal crystal structure (a = b = 0.5289 nm, c = 0.1042 nm) in chalcopyrite phase. Based on SEM imaging, the average particle size is ~ 100 nm, higher than the crystallite size (26 nm) obtained from Debye-Scherrer analysis, for NCs with growth time 30 minutes. The EDS measurement indicates the ratio of Cu, Fe, and S close to 1:1:2. Raman spectroscopy, determined using HeNe laser (632.8 nm), indicates active modes of vibrations at 290 (A1), 351 (B1), 470 (E) cm-1. A very strong absorption peak at ~ 465 nm was observed for CuFeS2 NCs with growth time 30 minutes or less. We will also discuss about the intermediate band absorption of these materials due to the empty Fe 3d orbitals. Similarly, these NCs-based films are p-type determined by thermal-probe measurement, and the average sheet resistance of the films are 7.3(±3.7) x104 Ω ■-1. Additionally, we will also address hole transport properties of these CuFeS2 materials in energy harvesting applications.