The heavier, the better — superior stability in isotope functionalized perovskites - Drs. Gang Liu and Lingping Kong

DECEMBER 4, 2020

New work from a team of scientists led by Drs. Gang Liu and Lingping Kong from HPSTAR employed high pressure tools to discover a significantly suppressed lattice disorder in isotope functionalized perovskite MAPbI₃, which is crucial for structural stability and extraordinary optoelectronic properties. Such improved lattice stability boosts its photoluminescence intensity by 3 folds previously unachievable without isotope doping. The result is published recently in  Advanced Functional Materials.

Organic-inorganic hybrid lead iodide perovskites are universally recognized as very promising photovoltaic (PV) materials. While outstanding PV performance is continuously reported, manipulating these hybrid perovskites for extraordinary optoelectronic properties with a greater intrinsic structural stability becomes a growing attention. The soft nature of organic–inorganic halide perovskites renders their lattice particularly tunable to external stimuli such as pressure, undoubtedly offering an effective way to modify their structure for extraordinary optoelectronic properties. However, these soft materials meanwhile feature a general characteristic that even a very mild pressure will lead to detrimental lattice distortion and weaken the critical light–matter interaction, thereby triggering the performance degradation.

Herein, an international research team led by scientists from Center for high pressure science and technology advanced research (HPSTAR) reported a comprehensive high-pressure isotope research on hybrid perovskites. To their surprise, it is observed that the pressure-driven lattice disorder can be significantly suppressed via hydrogen isotope effect, which is crucial for better optical and mechanical properties previously unattainable. By in situ neutron/synchrotron-based analysis and optical characterizations, a remarkable photoluminescence (PL) enhancement by threefold is convinced in deuterated CD₃ND₃PbI₃, which also shows much greater structural robustness with retainable PL after high peak-pressure compression–decompression cycle.

The researchers also proposed an atomic level understanding of the strong correlation among the organic sublattice and lead iodide octahedral framework and structural photonics, where the less dynamic CD₃ND₃⁺cations are vital to maintain the long-range crystalline order through steric and Coulombic interactions. In addition, the result of device-related investigations shows CD3ND3PbI3-based solar cell has comparable photovoltaic performance as CH₃NH₃PbI₃-based device but exhibits considerably slower degradation behavior, thus representing a paradigm by suggesting isotope-functionalized perovskite materials for better materials-by-design and more stable photovoltaic application.

Caption: Color plots of the pressure-dependent PL evolutions of CD₃ND₃PbI₃ (left) and CH₃NH₃PbI₃ (right) single crystals.