• Jones, Michael
• Sanchez, Bartomeu Monserrat
• Friend, Richard, H.
• Goor, Tim Van De
• Neumann, Timo
• Bourelle, Sean A.
• Feldmann, Sascha
• Deschler, Felix
• Winkler, Thomas
• Kelly, Nicola D.
• Liu, Cheng
• Dutton, S. E.

Abstract

Bandgap tuning of hybrid metal-halide perovskites by halide substitution holds promise for tailored light absorption in tandem solar cells and emission in LEDs. However, the impact of halide substitution on the crystal structure and the fundamental mechanism of photo-induced halide segregation remain open questions. Here, using a combination of temperature-dependent X-ray diffraction and calorimetry measurements, we report the emergence of a disorder- and frustration-driven orientational glass for a wide range of compositions in CH3NH3Pb(ClxBr1-x)3. Using temperature-dependent photoluminescence measurements, we find a correlation between halide segregation under illumination and local strains from the orientational glass. We observe no glassy behaviour in CsPb(ClxBr1-x)3, highlighting the importance of A-site cation for the structure and optoelectronic properties. Using first-principles calculations, we identify the local preferential alignment of the organic cations as the glass formation mechanism. Our findings rationalise the superior photostability of mixed-cation metal-halide perovskites and provide guidelines for further stabilisation strategies.

Topics

• perovskite
• photoluminescence
• x-ray diffraction
• glass
• glass
• calorimetry