Enhanced-performance of self-powered flexible quantum dot photodetectors by a double hole transport layer structure

Abstract

The usefulness of self-powered quantum dot (QD) photodetectors is increased if they are fabricated on flexible substrates. However, the performance of such photodetectors is typically significantly worse than similar devices fabricated on glass substrates due to poor charge transport performance. Here, a novel flexible self-powered CdSe_xTe_1−x QD photodetector with a double hole transport layer of PEDOT:PSS/P-TPD has been fabricated, which achieves a performance comparable to that of rigid devices. The energy level of the P-TPD layer matches well with that of the PEDOT:PSS and QD layers, which significantly enhances photodetection capability across a spectral region that spans the ultraviolet, visible and near infrared (UV-NIR). A low dark current density (1.03 × 10⁻⁶ mA cm⁻²) and a large specific detectivity of approximately 2.6 × 10¹² Jones at a wavelength of 450 nm are demonstrated, significantly outperforming previously reported flexible QD-based detectors. This improvement in performance is attributed to both increased hole transport efficiency and the inhibition of electron transport from the QDs into the PEDOT:PSS layer. The photodetector also exhibits good sensitivity under weak illumination, producing a photocurrent of 196 × 10⁻⁶ mA cm⁻² under an irradiance of 5 μW cm⁻². Moreover, no significant performance degradation is observed after 150 bending cycles to an angle of 60 degrees.