Pressure-induced 2D-3D conversion in hybrid lead iodide layered perovskite -Drs. Lingping Kong and Gang Liu
JULY 20, 2020
Hydrostatic pressurization can effectively lead to new and improved material properties. However, most of the novel material properties are only retainable at high-pressure states, and therefore warrant no practical applicability at ambient conditions. Recently, a team of international scientists led by Dr. Lingping Kong and Dr. Gang Liu from HPSTAR reported permanent and irreversible transition of 2D hybrid Dion-Jacobson lead iodide perovskite to 3D perovskite phase at ambient conditions after pressure treatment. This work suggests the usefulness of high-pressure technique in preparing materials for real-situation applications. The results, as reported in PNAS, marks crucial steps in utilizing pressure for ex-situ and ambient-environment applicability in engineering light-absorbing materials for high-performance optoelectronics and luminescence.
Harnessing the pressure-induced properties has been a long-standing effort in the quest of exotic materials at ambient environment. Nevertheless, due to the order-disorder-order and recrystallization behaviors of material structures, desirable properties attainable at high-pressure states tend to be reversed at ambient pressure. From this sense, choosing materials with modifiable basis is imperatively important for permanent change in properties. Being a class of 2D metal halide perovskites, Dion-Jacobson perovskites (structural formula: A'An-1BnX3n+1, A=CH3NH3+ (MA+), HC(NH2)2+, Cs+, B=Pb2+, Sn2+, X=I-, Br- and/or Cl-, A'=dication, n=1, 2, 3, ∞) represent a new material paradigm that is different from conventional Ruddlesden-Popper perovskite phase, in which D-J perovskites do not have the van der Waals gaps as encountered in R-P counterparts due to the divalent nature of interlayer organics. Such exotic structure ensures much shortened interlayer distance and greater structural rigidity, two important factors that can make sure irreversible structural phase transitions, and thus is electronically and atomically more resembling the 3D bulk phase. The scientist observed permanent and notable transition of 2D D-J phase (3AMP)(MA)3Pb4I13 to 3D MAPbI3 after 40 GPa pressure treatment, as proved by X-ray diffraction crystal structure after decompression.
Caption: 2D-3D transition in hybrid perovskites.
二维层状的Dion-Jacobson铅基碘化物钙钛矿是一种光伏领域的前沿材料，其兼具高性能和高化学稳定性的特点。在压力维度下，这类材料也产生了多种奇异的物理特性。在本研究中，研究者利用多种同步辐射先进表征手段，确认了压力下Dion-Jacobson钙钛矿的多层次转变行为，包括晶体-非晶转变、半导体-金属转变、以及二维-三维结构转变。更重要的是，在压力去除后，永久的结构和物性转变得以彻底实现，进而为实际应用提供了可能。