Rational design of an organic–inorganic hybrid with Schiff base cations for an efficient quadratic nonlinear optical switch

Abstract

Recently, impressive progress has been achieved on a new and brilliant scheme for a solid-state quadratic nonlinear optical (NLO) switch, which holds enormous potential for developing next-generation intelligent optoelectronic devices. However, most of them are still restricted by their poor switching capability and low operating temperature. Herein, we present a rational design approach for developing a highly efficient hybrid halide NLO switching material through introducing conjugated aromatic Schiff base cations. As expected, an organic–inorganic hybrid halide compound (C₁₀H₁₄N)PbBr₃ (1, C₁₀H₁₄N is N-propylbenzylideneaminium) has been developed, which exhibits highly efficient modulation of the quadratic NLO property (1.05 times that of KH₂PO₄) and a high phase transition temperature of 411 K. Besides, the second harmonic generation (SHG) powder test demonstrates that this material is phase matchable. Microscopic single-crystal structure analysis combined with theoretical calculations reveals that the high-performance NLO switching behaviour of 1 originates from the reversible ordered/disordered transformation of the aromatic Schiff base N-propylbenzylideneaminium cations accompanied by the re-orientation of the inorganic [PbBr₃]_∞ framework. More importantly, further investigations show that the conjugated effect of the Schiff base cations makes important contributions to the NLO properties of 1. This work opens up a new route for designing highly efficient quadratic NLO switches and provides a promising way to further develop high-performance solid-state phase transition materials (e.g. ferroelectrics) and intelligent optoelectronic devices.