In Situ Growth of Ruddlesden–Popper Perovskite Nanocrystals in Carbon Nanotubes for Brain-Inspired Optoelectronic Synapses

Two-dimensional Ruddlesden–Popper perovskites have emerged as promising materials for optoelectronic synapse applications due to their unique quantum confinement effects, tunable band gap, excellent photoresponse, and enhanced environmental stability. Their layered structure enables efficient charge transport and light absorption, which are essential for mimicking synaptic functionalities. Here, we report a photonic synapse device using Ruddlesden–Popper perovskite nanocrystals (RPNCs) grown inside the inner channels of multiwalled carbon nanotubes (MWCNTs), a unique approach that enhances the environmental stability and charge transfer efficiency. The fabricated device demonstrates synaptic functionalities, including paired-pulse facilitation (PPF), synaptic time-dependent plasticity (STDP), and long-term potentiation and depression (LTP/LTD), with memory retention exceeding 1000 s. Furthermore, our CNN-based image recognition study achieved 92% accuracy on MNIST and 85% accuracy on F-MNIST, highlighting the potential for neuromorphic computing applications. This approach offers significant advantages in material stability and low-power operation, making it a promising candidate for future optoelectronic and artificial vision systems.