Targeted regulation and optimization of multifunctional phase transition materials by novel void occupancy engineering

As an innovative form of stimulus-response materials, organic-inorganic hybrid phase transition materials have become a wonderful contender in the field of functional electronic equipment due to their versatile structure, intensive functions and straightforward preparation. However, the targeted regulation and optimization of the electrical/optical response, along with the establishment of regular structure-performance relationships, pose significant challenges in meeting the diverse demands of practical applications over an extended period. Herein, we conducted a systematic investigation into the role of lattice void occupancy in regulating phase transition temperature ( T p ) and related optical/electrical bistability. By taking hybrid material [TMEA][Cd(SCN) 3 ] featuring a flexible ammonium cation [TMEA] + (TMEA = ethyltrimethylammonium) as the prototype, we successfully synthesized three phase transition materials, namely [DEDMA][Cd(SCN) 3 ], [TEMA][Cd(SCN) 3 ] and [TEA][Cd(SCN) 3 ] (DEDMA = diethyldimethylammonium, TEMA = triethylmethylammonium, and TEA = tetraethylammonium), and the excellent regulation of the physical properties of these compounds was achieved through subtle engineering of void occupancy. More strikingly, [TEA][Cd(SCN) 3 ] exhibits remarkable bistable properties in terms of dielectric and nonlinear optical responses (with second-harmonic generation intensity reaching 2.5 times that of KDP). This work provides a feasible avenue to reasonably customise organic-inorganic hybrid phase transition materials and finely adjust their intriguing functionalities. Similar to a tossed stone raising a thousand ripples, it was found that a small structural mechanism associated with void occupancy has subtle influence on phase transition material physical properties in this work.