Tuning Self-Trapped Exciton Emission in 1D White-Light Emitting Perovskites Through Halide Composition and Synthesis Route

Low-dimensional halide perovskites (LDHPs) are promising candidates for optoelectronic applications, specifically light emission. LDHP's reduced-dimensional frameworks allow exceptional tunability of the optoelectronic properties. Self-trapped exciton emission (STE) is an intriguing characteristic of some LDHPs, offering a compelling mechanism for white-light emission. In this work, we study the effect of halide substitution and synthetic methods on the optical properties, with a particular focus on STE emission, of one-dimensional LDHPs using (2,5-dmpz)-Pb-(Br _<i>x</i> Cl_1-<i>x</i> )₄ (dmpz = dimethylammonium piperazine) as a model system, exhibiting high emission quantum efficiency and structural consistency. Mechanochemical approaches, including manual grinding and ball milling, were employed to synthesize pure and mixed halide compounds, enabling precise composition control. Structural characterization revealed that ball milling produces materials with improved crystallinity and a homogeneous halide distribution. Optical characterization showed an anticorrelation between the absorption onset and STE emission energies, with STE properties influenced by both halide composition and a synthesis route. Moreover, we found that the STE emission of the mixed halide compounds evolved with time. The post-synthesis evolution of the STE emission spectrum is associated with local lattice distortions rather than long-range structural changes. The emission quantum efficiency of these compounds was measured and reached a value of 35%, among the highest values measured for 1D broad emitters. These findings provide additional insights into the design of next-generation LDHP compounds exhibiting STE emission and development of white-light-emitting devices based on them.