A Low-Cost Approach to Fabricating Thin-Film Solar Cells: From Nanocrystals To Thin-Films

Within the Solar Economy IGERT (SEIGERT), a group of researchers develop and optimize a scalable process to fabricate low-cost thin-film solar cells for the demands of harvesting clean and inexpensive energy from sunlight. Utilizing the nanocrystal-based process developed in-house, the Cu2ZnSn(S1-ySey)4 (CZTSSe) thin-film solar cells demonstrate their potential by achieving total area 8.5% power conversion efficiency (PCE) under AM1.5 illumination. The method focuses on CZTS nanocrystals that are first synthesized and later selenized into a dense CZTSSe layer, which serves as the absorber material.
In order to understand the phase transition from nanocrystals to dense thin-films, the chemical compositions and crystal structures of multinary phases in nanocrystals and thin-films must be studied. CZTS nanocrystals with tunable Cu, Zn, and Sn contents and various crystal structures (kesterite/stannite and wurtzite) have been investigated and compared to the respective selenized thin-films by means of powder X-ray diffraction (PXRD), high-resolution transmission electron microscopy (HRTEM), and energy-dispersive X-ray spectroscopy (EDX).