Colloidal CdSe Quantum Dots and PQT-12-Based Low-Temperature Self-Powered Hybrid Photodetector

Abstract

In this letter, a novel dual junction self-powered hybrid photodetector is proposed using colloidal CdSe quantum dots (QDs) as an active layer (~50-nm thickness), and PQT-12 polymer as filter layer subsequently deposited on an ITO-coated glass substrate by the spin coating method. The colloidal CdSe QDs are deposited on the PQT-12 film at 80 °C, which is much smaller than the growth temperature (usually >300 °C) of the inorganic layer of other reported hybrid self-powered detectors. The Au metal dots are deposited on the CdSe QD layer for anode electrodes while the ITO acts as the cathode electrode of the device. Two asymmetric depletion widths formed at PQT-12/CdSe and Au/CdSe junctions at two sides of the active layer controls the operation of the proposed detector. The photodetector shows band-pass response over the visible spectrum with a sharp cutoff for higher wavelengths at ~610 nm. The maximum responsivity and detectivity of the self-powered photodetector are achieved to be ~3.3 mA/W and $5.4\times 10^{9}$ cmHz $^{1/2}\text{W}^{-1}$ , respectively, at a wavelength of ~420 nm under the optical power density of $\sim 130\mu \text{W}$ /cm2. The rise time and fall time of the device are found to be ~12.01 and ~15.32 ms, respectively.