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 photodetector comprising:
a plurality of pixel regions, each pixel region having a respective first electrode and a respective second electrode;
an optically sensitive material between the first electrode and the second electrode;
a transistor coupled to the respective first electrode in electrical communication with the optically-sensitive material, the transistor including a gate configured to store charge, wherein the first electrode of a pixel region electrically communicates with the gate, wherein charge stored at the gate is discharged by a flow of current through the optically sensitive material during an integration period of time, and wherein the second electrode is configured to be at a second potential;
circuitry generating a signal from the gate based on the amount of charge remaining in the charge store after the integration period of time, where, under a low-light illumination condition, a first average potential difference is established between the first electrode and the second electrode, where, under a higher-light illumination condition relative to the low-light condition, a second average potential difference is established between the first electrode and the second electrode, the second average potential difference being at least 0.5 V smaller in amplitude than the first average potential difference, and where a responsivity of the optically sensitive material is at least two times lower under the higher-light condition than under the lower-light condition;
a pixel region comprising the optically sensitive material;
pixel circuitry electrically coupled to the optically sensitive material, the pixel circuitry to establish a voltage over an integration period of time, wherein a signal is generated based on the voltage after the integration period of time, the signal having a noise level, wherein a rate of current flow through the optically sensitive material at relatively high light levels causes the voltage to remain above a minimum threshold as a result of a non-linear relationship between the voltage and an intensity of light absorbed by the optically sensitive material of the respective pixel region, and wherein generating of the signal occurs when the voltage is greater than the minimum threshold;
a converter configured to convert the signal into digital pixel data, wherein the converter has an input range; and
at least one of the pixel circuitry and the optically sensitive layer to provide a dynamic range more than at least twice the ratio of the input range of the converter divided by the noise level.
2. A photodetector comprising:
a pixel region, each pixel region having a first electrode and a second electrode;
a plurality of layers of optically sensitive material between the first electrode and the second electrode;
a transistor coupled to the optically sensitive material, the transistor including a gate configured to store charge, wherein the respective first electrode of the pixel region electrically communicates with the gate, wherein charge stored at the gate is discharged by a flow of current through the optically sensitive material during an integration period of time; and
circuitry generating a signal from the gate based on the amount of charge remaining in the charge store after the integration period of time, where, under a low-light illumination condition, a first average potential difference is established between the first electrode and the second electrode, where, under a higher-light illumination condition relative to the low-light condition, a second average potential difference is established between the first electrode and the second electrode, the second average potential difference being at least 0.5 V smaller in amplitude than the first average potential difference, and where a responsivity of the optically sensitive material is at least two times lower under the higher-light condition than under the lower-light condition.