ZnO‐Based Ultraviolet Photodetectors with Tunable Spectral Responses

Conventionally, wavelength‐selective ultraviolet photodetection is achieved by using broadband inorganic photodiodes coupled with optical filters, which significantly increases the complexity and fabricating cost of devices for high pixel density imaging systems. Here, a facile approach to achieve tunable spectral response without filters is demonstrated. The devices are based on ZnO heterojunctions, and the response spectra are effectively modulated by tuning the position of charge generation, which results in distinct charge‐collection efficiencies. After optimization, the ZnO/poly[bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine] (PTAA) photodiodes exhibit narrowband ultraviolet (UV) response with a full width at half maximum (FWHM) of <25 nm, and the NiO x /ZnO devices reveal relatively broader photoresponse. All of these devices demonstrate relatively low dark currents and noises, high responsivities and detectivities, and fast response speeds. This work proves the great potential of ZnO thin films for UV detection and also first provides an alternative approach to effectively tune the spectral response.