High-performance self-powered photodetectors achieved through the pyro-phototronic effect in Si/SnOx/ZnO heterojunctions

Highlights: • Performance of the photodetectors are enhanced by coupling the photovoltaic and pyroelectric effects. • The pyro-phototronic effect is demonstrated for the first time in a n-p-n heterojunction. • An optimum responsivity and detectivity of 36.7 mA/W and 1.5 × 10¹¹ Jones were achieved at zero bias. • Ultrafast rise and fall times of 3 and 2 µs were achieved for Al/Si/SnO_x/ZnO/ITO devices. Coupling together the pyroelectric effect and the photovoltaic effect is a novel method to significantly enhance the performance of photodetectors. In this work, we make use of this effect through a tri-layered heterojunction of n-Si/p-SnO_x/n-ZnO, which takes advantage of the pyroelectric properties of the n-type ZnO film and the photovoltaic response of the n-type Si/p-type SnO_x heterojunction. The photo-response of the device, with excitation from a 405 nm wavelength laser, is carefully investigated, and it is shown that the photodetector performance is improved with increased chopper frequency owing to the coupled photovoltaic-pyroelectric effect. The Al/Si/SnO_x/ZnO/ITO device exhibits an optimum responsivity and detectivity of 36.7 mA/W and 1.5 × 10¹¹ Jones, respectively, with a laser power density of 36 mW/cm² and at a chopper frequency of 400 Hz. Ultrafast rise and fall times of 3 and 2 µs, respectively, were obtained. Moreover, by using a 650 nm wavelength laser source, the responsivity and detectivity were improved up to 64.1 mA/W and 2.4 × 10¹¹ Jones, respectively. The performance of these photodetectors is approximately twice as fast as other pyro-phototronic devices, and exhibits comparable photodetector characteristics when compared to perovskite/Si heterojunction and transition metal dichalcogenides lateral heterojunction devices. Therefore, by combining a pyroelectric ZnO film with a solar cell into one single structure, photodetectors based on the pyro-phototronic effect have been developed that demonstrate state-of-the-art performance. The devices show great promise for visible ultrafast photosensing.