Multi‐Color Synaptic Luminescence in RE‐Doped Ca₂SnO₄ (RE = Sm³⁺, Er³⁺, and La³⁺)

Abstract Recently, there has been a surge of interest in neuromorphic computation inspired by the extraordinary characteristics of the human brain, such as low energy consumption, parallelism, adaptivity, cognitive abilities, and learning capabilities. Significant research efforts have focused on exploring optical synaptic behaviors in various functional materials. In this study, the potential of red, green and blue (RGB)‐colored long‐persistent luminescence (LPL) in Sm 3+ /Er 3+ /La 3+ ‐doped Ca 2 SnO 4 is investigated for synaptic functionality. The luminescence of the samples is continuously enhanced under serial photoexcitation pulse applications, that is, the potentiation process, which is a key feature demonstrated in biological synapses. In addition, multichannel synaptic functionalities in the full‐color range is successfully demonstrated by integrating individual RGB‐colored Sm 3+ /Er 3+ /La 3+ ‐doped Ca 2 SnO 4 into a single quantity. To validate the optical synaptic behavior of the samples in neuromorphic computing applications, a reservoir computing (RC) simulation is performed for space‐time data processing using the unique responses of the samples under 4‐bit excitation pulses. The results demonstrated that the multi‐channel synaptic behaviors in the samples should be more valid for utilization in the RC layer than the single channel of synaptic behavior. We suggest this exploration holds promise for the advancement of synaptic devices employing LPL materials.