Photocurrent response in chemically deposited CdS thin films

Highly photosensitive CdS thin films with photocurrent to dark current ratios (Iph/Id) of ∼106–107 under AM2 illumination are reported. The films are prepared by an electroless chemical deposition technique. The optical microscopy along with the optical transmission spectra of the films revealed a continuous thin film ∼ 0.3–0.5 μm in thickness and with an overgrowth of single crystallites of about ∼10–20 μm in diameter. The reasons for the high photosensitivity of the freshly prepared films and the increase in the Iph/Id value upon storage are discussed. The time response of the photocurrent, an aspect which is rarely mentioned in the literature on chemically coated CdS films, is explicitly presented.