Mechanochromic Luminescence of Composites Based on (CH3NH3)PbBr3 and Layered HPs: Influence of 2D Components and Interface Multilayered Phases

The mechanochromic luminescence (MCL) properties of crystallized powders of composites based on the 3D perovskite MAPbBr(3) and one layered (2D) halide perovskite (HP) are reported for three 2D HPs selected for their distinct emission properties: (PEA)(2)PbBr4 (n=1) narrow emission (HE), (EDBE)PbBr4 (m=2) broad emission (LE) and (BA)(2)PbBr4 (n=1) dual emission (HE and LE). All composites exhibit sensitive MCL due to the activation of the 3D component emission through energy transfer (ET) from multilayered perovskites formed at the interface. While the excitonic HE band is less affected by the mechanical treatment, LE is quenched in crushed composites, suggesting that it rather originates from the crystal edge/surfaces. Full reversibility of the MCL process is obtained only when the multilayered phases formed at the interface are not stable. The emission of composite thin films, where larger 2D/3D interface areas are present, further support the role of the interfaces in the activation of 3D emission.