Colossal photodetection enhancement via plasmon–exciton synergy in ultra-smooth CsPbBr3 microplates†

Abstract

All-inorganic perovskites have a high absorption coefficient, long carrier diffusion length, large carrier mobility, tunable direct bandgap and good ambient stability and are therefore considered as an ideal candidate for the new generation of optoelectronic devices. Many methods have been used to improve their photoresponsive performances, among which localized surface plasmon resonance (LSPR) is a very effective means. Theoretically, the enhancement effect of LSPR is strongly dependent on the relationship between the LSPR wavelength and material, but related research has not been reported until now due to the challenge of fabricating perovskite materials with an atom-level smooth surface. Herein, we successfully developed a simple polydimethylsiloxane (PDMS)-assisted slow evaporation route to fabricate plenty of supersmooth CsPbBr₃ microplates with a mean surface roughness of only 0.6 nm. Subsequently, gold nanospheres (Au NSs) were deposited on the surface of the perovskite microplates to examine the effect of the diameter of the gold nanospheres on the LSPR wavelength. Based on photoluminescence (PL), dark-field scattering spectroscopy and finite-difference-time-domain (FDTD) simulation results, the optimal Au NS diameter was found to be nearly equal to an LSPR wavelength of 60 nm, where the Au NSs and CsPbBr₃ microplates had the strongest coupling effect. In contrast with a pristine CsPbBr₃ microplate, the on/off ratio of the CsPbBr₃ microplate covered with Au NSs was observed to increase from 109 to 448 and responsivity could reach as high as 8430 mA W⁻¹, which is comparable to many other excellent perovskite-based photodetectors. An ultrahigh plasmonic enhancement factor of about 1145% was suggested to be responsible for the excellent photoresponsive performance of the hybrid Au NS-CsPbBr₃ photodetector. Our research may shed new light on accelerating the development of visible-light detectors based on perovskite materials.