This study reports a self-powered, broadband artificial synapse based on screen-printed thermoelectric silver selenide for in-sensor computing. Spatially dependent photo-thermoelectric responses allow a single device to emulate both excitatory and inhibitory synaptic behavior across wavelengths from 405 to 1550 nm. The device also demonstrates synaptic plasticity and NOT and XOR logic operations. A convolutional neural network built with the synapse was used for smile detection, gender recognition, and image recognition, illustrating its potential for integrated optical sensing and computation.