Colossal Photodetection Enhancement via Plasmon-Exciton Synergy in Ultra-Smooth CsPbBr3 Microplates

Abstract

All-inorganic perovskites have high absorption coefficient, long carrier diffusion, large carrier mobility, tunable direct bandgap and nice ambient stability, which are believed as ideal candidate for the new generation of optoelectronic devices. Many methods have been used to improve their photoresponse performances, among which the localized surface plasmon resonance (LSPR) is a very effective way. Theoretically, the enhancement effect of LSPR is strongly dependent on the relationship between LSPR wavelength and material, but the related research hasn’t emerged until now due to the challenge of fabricating perovskite material with atom-level smooth surface. Here, we have 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) are deposited on the surface of perovskite microplates to research the effect of the diameter of gold nanospheres on the LSPR wavelength. Based on the Photoluminescence (PL), dark-field scattering spectroscopy and finite-difference-time-domain (FDTD) simulation results, the optimal Au NS diameter is nearly equal to the LSPR wavelength of 60 nm, where Au NS and CsPbBr3 microplate have the strongest coupling effect. In contrast with pristine CsPbBr3 microplate, the on/off ratio of the CsPbBr3 microplate covered by Au NS is seen to increase from 109 to 448 and the responsivity can reach as high as 8430 mA/W, which is comparable to many other excellent perovskite-based photodetectors. The ultrahigh plasmonic enhancement factor of about 1145 % is suggested to be responsible for the excellent photoresponse performance of the hybrid Au NS-CsPbBr3 photodetector. Our research may shed new light on accelerating the visible-light detection development of perovskite materials.