David Mitzi1
Duke University1
Multinary chalcogenides play an important role in both commercial and emerging photovoltaic (PV) and photoelectrochemical (PEC) devices. I<sub>2</sub>-II-IV-X<sub>4</sub> multinary semiconductors, wherein “I” is Ag or Cu, “II” is a divalent metal or alkaline earth, “IV” is a tetravalent metal and “X” is a chalcogen (generally S or Se), have formed a particularly interesting branch of emerging solar absorbers, with a target of replacing more traditional systems such as CdTe or Cu(In,Ga)(S,Se)<sub>2</sub> that suffer from toxicity or elemental abundance issues. Large efforts have focused on Cu<sub>2</sub>ZnSn(S,Se)<sub>4</sub> as an earth-abundant and reduced-toxicity system, leading to significant performance improvement. However, similarity of component atom sizes and preferred coordination among these atoms give rise to facile anti-site defect formation, which in turn has placed a limit on performance improvement. In this talk we will explore a broader class of I<sub>2</sub>-II-IV-X<sub>4</sub> (I = Ag, Cu; II = Ba, Sr, Pb; IV = Si, Ge, Sn; VI = S, Se) multinary semiconductors wherein larger “II” atoms are incorporated, thereby leading to an expectation of reduced propensity toward anti-site defect formation. Recent results targeting predictive approaches for understanding structural/phase stability [1,2], defect/property studies [3,4] and solar cell devices [3-6] will be addressed for this family. If desirable electronic structure tunability associated with a multi-element stoichiometry can be combined with earth-abundant components and control over defect formation, this emerging family of multinary chalcogenides may provide a path forward in the quest for high-performance, low cost and scalable PV and PEC devices.<br/><br/><b>References:</b><br/>[1] J.-P. Sun, G. C. McKeown Wessler, T. Wang, T. Zhu, V. Blum, D. B. Mitzi, “Structural Tolerance Factor Approach to Defect-Resistant I<sub>2</sub>-II-IV-X<sub>4</sub> Semiconductor Design” <i>Chem. Mater.</i> 32, 1636 (2020); [2] G. C. McKeown Wessler, T. Wang, J.-P. Sun, Y. Liao, M. Fischer, V. Blum, D. B. Mitzi, “Structural, optical, and electronic properties of two quaternary chalcogenide semiconductors: Ag<sub>2</sub>SrSiS<sub>4</sub> and Ag<sub>2</sub>SrGeS<sub>4</sub>” <i>Inorg. Chem.</i> 60, 12206 (2021); [3] Y. Kim, H. Hempel, S. Levcenco, J. Euvrard, E. Bergmann, O. Gunawan, T. Unold, I. G. Hill, D. B. Mitzi, “Optoelectronic property comparison for isostructural Cu<sub>2</sub>BaGeSe<sub>4</sub> and Cu<sub>2</sub>BaSnS<sub>4</sub> solar absorbers” <i>J. Mater. Chem. A</i> 9, 23619 (2021); [4] B. Teymur, S. Levcenco, H. Hempel, E. Bergmann, J. A. Márquez, L. Choubrac, I. G. Hill, T. Unold, D. B. Mitzi, “Optoelectronic and material properties of solution-processed Earth-abundant Cu<sub>2</sub>BaSn(S, Se)<sub>4</sub> films for solar cell applications” <i>Nano Energy</i> 80, 105556 (2021); [5] Y. Kim, D. B. Mitzi<i>, ACS Appl. Energy Mater.</i> 4, 11528 (2021); [6] J. Song, B. Teymur, Y. Zhou, E. Ngaboyamahina, D. B. Mitzi, “Porous Cu<sub>2</sub>BaSn(S,Se)<sub>4</sub> film as a photocathode using non-toxic solvent and a ball-milling approach” <i>ACS Appl. Energy Mater.</i> 4, 81 (2021).