Date/Time: 04-03-2018 - Tuesday - 05:00 PM - 07:00 PM
Pierre Poudeu1 Erica Chen1 Logan Williams1 Emmanouil Kioupakis1

1, Univ of Michigan, Ann Arbor, Michigan, United States

Photovoltaic research activities over the past decades have focused on the development of low-cost highly efficient materials for application as absorbers in photovoltaic technologies. Popular material systems under consideration in recent years include metal-halide perovskite, organic-inorganic hybrid perovskite, and copper chalcogenide semiconductors such as CuIn1-xGaxSe2 (CIGS). The large absorption coefficient of these materials coupled to the ability to engineer their bandgap through chemical substitutions enable the realization of solar cells devices with power conversion efficiency exceeding 20%. Despite the promise of these material systems, thermal instability associated with hybrid perovskite, restriction on the use of heavy metals (Cd, Pb etc.) and the limitation in supply for In are roadblocks to large scale deployment of the existing leading perovkite and chalcogenide-based technologies. To address these issues, earth abundant copper chalcogenides such as kesterites, Cu2SnZn(S,Se)4 (CZTS), that can be obtained through chemical substitution of In3+ atoms in CuIn(S,Se)2 by Zn2+ and Sn4+, have been investigated. However, the efficiencies of solar cell devices based on these materials remain around 12.6% due to unavoidable anti-site defects such as CuZn and ZnCu. It therefore appears that achieving low-cost, earth abundant copper chalcogenide solar cells with high efficiency requires the development of novel compositions with new crystal structure rather than a simple variation of the chemistry of existing structures. In this work, we report for the first time on the Earth-abundant ternary copper titanium selenide, CTSe, as a promising light-absorbing material for the fabrication of ultra-thin low-cost high efficiency solar cell devices. CTSe is a p-type semiconductor featuring indirect (1.15 eV) and direct (1.34 eV) bandgaps, which are both desirable for ideal solar absorber materials. It crystallizes in a new noncentrosymmetric cubic structure (space group F-43c) in which CuSe4 tetrahedra share edges and corners to form the octahedral anionic clusters, [Cu4Se4]4-, which in turn share corners to build the three dimensional framework, with Ti4+ ions located at tetrahedral interstices within the channels. This unique structural feature results in large density of states (DOS) and relatively flat bands near the band edges, which are believed to be responsible for the ultra-large absorption coefficients (~105 cm-1) observed throughout the visible range for CTSe thin-film. These findings point to CTSe as a promising solar absorber material for scalable low-cost high-efficiency thin-film solar cells.

Meeting Program

5:00 PM–7:00 PM Apr 3, 2018 (America - Denver)

PCC North, 300 Level, Exhibit Hall C-E