Self-powered ZnO-based pyro-phototronic photodetectors: impact of heterointerfaces and parametric studies

A photoresponse can be classified based on the mode of generation of an electrical signal upon interaction with the photons, such as in the photovoltaic effect, the bolometric effect, the photogating effect, the photoconductive effect, the photothermoelectric effect and the pyro-phototronic effect, etc. The photovoltaic effect has been implemented to design self-powered photodetectors (PDs), and further, the pyro-phototronic effect has been used for augmenting the performance of PDs. The pyro-phototronic effect is an amalgamation of the generation of carriers due to photoinduction, transportation of the generated charge carriers and their recombination. The basic principles and properties of the pyro-phototronic effect have been studied thoroughly by analyzing the process of charge transfer and the current response time of PDs upon light illumination. Zinc oxide (ZnO) has been well exploited for numerous applications due to its direct bandgap for photodetection and its piezoelectric properties for sensors and actuators. Thus, it efficiently contributes to both the pyroelectric and pyro-phototronic effects. Numerous approaches have revealed the modulation of pyro-phototronic current using heterointerfaces with ZnO, which include doping, heating, bandgap tuning, etc., for the self-powering capability of PDs. This review article summarizes the efforts toward developing self-powered PDs using ZnO-based heterointerfaces for an improved pyro-phototronic effect. ZnO-based materials with the pyro-phototronic effect, doped ZnO-based materials with the pyro-phototronic effect and ZnO-based materials with the plasmonic effect are discussed in detail. Highlighting various research directions, this article concludes with a discussion on the present challenges in state-of-the-art technology and the possible directions of future research in the field.