About the Seminar:

Hybrid organic-inorganic perovskites (HOIPs) have shown exceptional advances in photovoltaic applications due in part to their unique defect-tolerant frameworks that enables facile, inexpensive synthetic methods.1 Although their defect tolerance offers robust properties, it also serves as barrier for controllable doping. The low formation energy of intrinsic defects in conjunction with associated dynamic disorder serve to counteract intentional tuning of HOIP Fermi levels.2 In order to intentionally dope HOIP materials, a better understanding of the intrinsic defect compensation mechanisms and equilibria is required. A class of HOIPs know as 3D “hollow” HOIPS have been found to exhibit increased air stability which has been hypothesized to relate to their unique defect chemistry. In this talk, an overview of the thermodynamic origins of the increased stability seen in 3D “hollow” HOIPs will be given to yield insight into related defect equilibria. In the primary literature, configurational entropy was found play a significant role in the stabilization of the 3D “hollow” HOIPS, (A)1-x(en)x(Pb)1-0.7x(X)3-0.4x (A = methylammonium, formamidinium, en = ethylenediammonium, X = Br, I).3 These results indicate that the relative “hollowness” of these compounds influences their configurational entropy, stability, and defect equilibria.  

1. Brandt, R. E.; Poindexter, J. R.; Gorai, P.; Kurchin, R. C.; Hoye, R. L. Z.; Nienhaus, L.; Wilson, M.W. B.; Polizzotti, J. A.; Sereika, R.; ˇZaltauskas, R.; Lee, L. C.; MacManus-Driscoll, J. L.; Bawendi, M.; Stevanovi ́c, V.; Buonassisi, T. Searching for “Defect-Tolerant” Photovoltaic Materials: Combined Theoretical and Experimental Screening. Chemistry of Materials, 2017, 29, 4667–4674,
2.  Walsh, A.; Scanlon, D. O.; Chen, S.; Gong, X. G.; Wei, S.-H. Self-Regulation Mechanism for Charged Point Defects in Hybrid Halide Perovskites. Angewandte Chemie, 2014, 54, 1791–1794. 
3. Jayanthi, K.; Spanopoulos, I.; Zibouche, N.; Voskanyan, A. A.; Vasileiadou, E. S.; Islam, M. S.; Navrotsky, A.; Kanatzidis, M. G. Entropy Stabilization Effects and Ion Migration in 3D “Hollow” Halide Perovskites. J. Am. Chem. Soc., 2022, 144, 8223–8230.