A method is for measuring light energy received by a pixel including a transfer transistor, and a photodiode including a charge storage region. The method may include encapsulating the gate of the transfer transistor of the pixel in a semiconductor layer, at least one part of which includes a hydrogenated amorphous semiconductor. The method also may include grounding the charge storage region of the pixel, and determining the drift over time in the magnitude of the drain-source current of the transfer transistor.