The perovskite material can be used to build artificial retinas  

Researchers have built an artificial retina made of perovskite that can detect light in a similar way to the human eye.  In tests, the device was even able to recognize handwritten numbers.  

The eyes of humans and other mammals work thanks to light-sensitive cells in the retina, rods and cones, which absorb incoming photons and send electrical signals to the brain.  In this study, the researchers set out to simulate this process in a man-made device.  

The key ingredient in the device is perovskite, which absorbs light efficiently and, as such, could be a "front-runner" in the next generation of solar cells.  To do this, the team used light absorption to create sensors.  

The researchers embedded perovskite nanocrystals into the polymer and then sandwiched the layer between two electrodes -- aluminum at the bottom and indium tin oxide at the top.  The top of the electrode is etched to allow light to pass through the perovskite layer, forming an array of photoreceptors.  These are made on polyimide substrates that allow the device to bend and twist into whatever shape it needs, for example, the shape of a human retina.  

To process the light input, the sensor array is connected to a CMOS sensor and a neural network with 100 output neurons.  In tests with a 4×4 array, the device was illuminated using leds of various colors and was found to have an optical response very similar to the human eye, with the system particularly sensitive to green light.  In other tests, the system was even able to identify handwritten numbers with 72 percent accuracy.  It was also remarkably stable, with no change in response to light after 129 weeks.  

Despite the device's biological inspiration, artificial retinas are difficult to transplant into humans.  With more development, the device will be used to create more advanced vision systems for cameras and robots, the team said.