Dark current reduction in image sensors via dynamic electrical biasing

An image sensor, comprising:

• a semiconductor substrate;
• a plurality of pixel regions, each pixel region comprising an optically sensitive material over the substrate, the optically sensitive material positioned to receive light;
• a bias electrode for each pixel region, the bias electrode configured to provide a bias voltage to the optically sensitive material of the respective pixel region;
• a pixel circuit for each pixel region, each pixel circuit comprising a charge store formed on the semiconductor substrate and a read out circuit, the charge store being in electrical communication with the optically sensitive material of the respective pixel region, the pixel circuit being configured to reset the voltage on the charge store to a reset voltage during a reset period, the pixel circuit further being configured to integrate charge from the optically sensitive material to the charge store during an integration period, the pixel circuit being further configured to read out a signal from the charge store during a read out period, the bias voltage during the integration period being configured to be greater than the reset voltage.

A method of detecting an image, the method comprising:

• resetting the voltage of a charge store to a reset voltage during a reset period;
• applying a bias voltage across an optically sensitive material during an integration period;
• varying the charge on the charge store during the integration period based on the intensity of light incident on the optically sensitive material during the integration period;
• reading out a signal from the charge store during a read out period;
• varying a reference voltage on a reference voltage node, the reference voltage on the reference voltage node being used to reset the voltage of the charge store during the reset period, the reference voltage on the reference voltage node being used for read out of the signal from the charge store during the read out period.

A method of detecting an image comprising:

• resetting the voltage of a charge store to a reset voltage during a reset period;
• applying a bias voltage across an optically sensitive material during an integration period;
• varying the charge on the charge store during the integration period based on the intensity of light incident on the optically sensitive material during the integration period;
• and
• reading out a signal from the charge store during a read out period;
• wherein the bias voltage during the integration period is greater than the reset voltage.