Self-powered, filter-free, and fast solar-blind photodetectors enabled by luminescent converters with giant Stokes shift

Abstract

Solar-blind photodetectors (SBPDs) are commonly plagued by trade-offs among superior spectral selectivity, high responsivity, and rapid photoresponse speed. Herein, we report a self-powered SBPD integrated with an Er3+-doped metal halide luminescent converter, nominal composition Cs2Ag0.3Na0.7In0.6Er0.4Cl6, which features an enormous Stokes shift. This luminescent medium converts deep-ultraviolet (DUV) photons into visible emission, which is subsequently captured by a commercial silicon photodiode (Si PD). The converter realizes two integrated functions simultaneously: highly efficient DUV-to-visible photon conversion and intrinsic visible-light rejection, thereby removing the requirement for additional external optical filters. Operated under zero bias, the fabricated device delivers a remarkable responsivity of 226.7 mA/W upon 280 nm irradiation at an optical power of 10 μW, an eightfold enhancement relative to the pristine Si PD. Meanwhile, the photodetector exhibits a prominent photo-to-dark current ratio of approximately 4500. More importantly, the system exhibits an ultrafast photoresponse, with rise and fall times measured at 143 and 77 μs, respectively, which is about three orders of magnitude faster than typical Ga2O3-based SBPDs limited by persistent photoconductivity. The proposed design circumvents the intrinsic material drawbacks of conventional wide-bandgap semiconductors, establishing a strategy for low-cost, high-speed solar-blind photodetection.