Halide Perovskite Mem-Emitter for Analog Salience Processing

To sense is the ability to extract critical information from the environment. However, in a realistic scenario, we are often exposed to a myriad of stimuli at the same time. To effectively scan across them, the objects in the image can be processed based on their saliencies and a set of regulatory equations. Since these differential equations are dependent on inputs from the near history, processing them sequentially with digital computers (physically separated memory and processing units) would be very inefficient. Analog computing in modern applications is revisited for its efficient use of resources (power and footprint). To emulate the neuronal processes in analog fashion, the three device functionalities required are the interconnectivity, distinct wavelengths and the temporal dependencies of the transmission. In contrast to electrical physical wiring, higher levels of interconnectivity can be achieved by emitter-based systems processing information with light as the transmission medium. Here, we fabricated a mem-emitter (memory emitter) device comprising of an organic emitter and a perovskite emitter. The mem-emitter device has dual distinct emission wavelengths. Initially, the red organic emitter is first activated due to the small recombination zone spatially located at the organic emitter layer. However, with repeated electrical pulsing, ionic drift in the halide perovskite layer results in the widening of the recombination zone, enabling the green perovskite layer to emit. As a result, the emission spectra from the device not only depends on the present input but also the operational history of the device as well. We first studied the widening of the recombination zone; both the electroluminescence and photoluminescence spectra of the bilayer stack are compared. Interestingly, the photoluminescence spectra did not exhibit any emission from the red organic emitter. This highly suggests that the color change is not due to reabsorption but a spatial shift in recombination zone. Furthermore, we have optimized the pulse operation conditions for the mem-emitter device, achieving a dynamic gain of 470% in the green emission. Finally, we showcase two use cases of our mem-emitter device in analog temporal processing. Firstly, the temporally dependent green emission represents the self-inhibitory process in a salience processing network. For the first time, with a physical circuit comprising of mem-emitters and photodiodes, we managed to emulate inhibition of return - a key adaptive functionality in salience processing. Secondly, we utilize an array of mem-emitter devices as a physical salience heatmap display for the first time. With optimized pulse schemes, our mem-emitter array is capable of encoding analog salience values into distinct emissive colors – red, orange and green. With its dynamic temporal memory, the proposed dual wavelength mem-emitter device offers significant advantages in efficient salience processing with fewer components and smaller energy consumption.