Materials, systems and methods for optoelectronic devices
A photodetector is described along with corresponding materials, systems, and methods. The photodetector comprises an integrated circuit and at least two optically sensitive layers. A first optically sensitive layer is over at least a portion of the integrated circuit, and a second optically sensitive layer is over the first optically sensitive layer. Each optically sensitive layer is interposed between two electrodes. The two electrodes include a respective first electrode and a respective second electrode. The integrated circuit selectively applies a bias to the electrodes and reads signals from the optically sensitive layers. The signal is related to the number of photons received by the respective optically sensitive layer.
1. A method comprising:
providing an optically sensitive material;
causing a current to flow through the optically sensitive material during an integration period of time by providing a voltage difference across the optically sensitive material and exposing the optically sensitive material to light, wherein the rate of the current flow through the optically sensitive material depends upon the voltage difference across the optically sensitive material and intensity of the light absorbed by the optically sensitive material;
using the current flow through the optically sensitive material to discharge a portion of charge from a charge store during the integration period of time;
varying both the voltage difference across the optically sensitive material and the rate of the current flow through the optically sensitive material during at least a portion of the integration period; and
generating a signal based on the amount of charge remaining in the charge store after the integration period of time.
2. A photodetector comprising:
a pixel region comprising an optically sensitive material;
pixel circuitry electrically coupled to the optically sensitive material, the pixel circuitry causing a current to flow through the optically sensitive material during an integration period of time by providing a voltage difference across the optically sensitive material when the optically sensitive material is exposed to light, wherein the rate of the current flow through the optically sensitive material depends upon the voltage difference across the optically sensitive material and intensity of the light absorbed by the optically sensitive material, wherein the current flow through the optically sensitive material discharges a portion of charge from a charge store during the integration period of time, wherein both the voltage difference across the optically sensitive material and the rate of the current flow through the optically sensitive material vary during at least a portion of the integration period while the intensity of the light is substantially constant; and
read out circuitry generating a signal based on the amount of charge remaining in the charge store after the integration period of time.