Stable Whispering Gallery Mode Lasing from Solution‐Processed Formamidinium Lead Bromide Perovskite Microdisks

Abstract

Formamidinium (CH(NH2)2, FA) lead halide perovskites exhibit excellent optoelectronic properties for the applications of light‐emitting diodes and lasers. However, the reported formamidinium lead bromide (FAPbBr3) perovskite‐based lasers mainly depend on the external feedback or Fabry–Pérot mode cavities and suffer from moderate quality (Q) factors. Herein, solution‐processed square and quasi‐circular FAPbBr3 microdisks are developed to achieve room‐temperature naturally facet‐formed whispering gallery mode (WGM) lasers. These microdisks exhibit relatively high Q factor and tunable laser modes with threshold of 10–70 µJ cm−2 under 400 nm excitation. Although the synthesized circular microdisk is not regular enough, it still shows higher Q factor of 3455 than that of square microdisk due to the less boundary wave and pesudointegrable leakage. This simple and low‐cost solution processed method can tackle the complicated and expensive conventional preparation techniques of circular microdisks. Power dependent photoluminescence decay transients indicate that the band edge emission of the FAPbBr3 microdisks originates from free carrier recombination. In addition, these microdisks show high photostability and that room temperature lasing can sustain over 50 min. These results suggest that FAPbBr3 microdisks can serve as promising WGM lasers with excellent light emission capability and stability toward practical optoelectronic applications.

Highly Stable Lasing from Solution‐Epitaxially Grown Formamidinium‐Lead‐Bromide Micro‐Resonators

“…The laser threshold of 3 µJ cm -2 we found to be lower than those reported in the literature for both, FAPbBr 3 microdisks and nanowires. [12,27] In comparison to other lead halide perovskite laser structures, this threshold is within the best 20% of the values reported so far for lead halide perovskites (Table S1, Supporting Information). The FWHM of the lasing peak corresponds to a quality factor Q = λ/FWHM of ≈546, which is relatively low for a solution-processed lead halide perovskite laser resonator (see Table S1, Supporting Information).…”

“…Although the high potential of MHPs for lasing has been proven in respect to stability, [12][13][14] low lasing threshold, [7,15,16] high coherence and high-quality factor in the literature, [17][18][19] presenting various resonator geometries, [15,[17][18][19][20][21][22][23][24][25][26][27][28] only a few reports exist about lasing from epitaxial MHPs. All the epitaxial lasers have been prepared by the CVD method, that is, by depositing either all-inorganic CsPbX 3 or MAPbBr 3 on substrates with a different crystal structure as the perovskites, such as mica or GaN.…”

Review of biosensing with whispering-gallery mode lasers

“…The energy bandgap is directly related to the chemical structure of the perovskite, and its manipulation allows the full visible range to be covered in WGM microlasers. WGM lasing has been demonstrated in a number of perovskite structures with different shapes such as formamidinium lead bromide perovskite microdisks 108 , CsPbBr 3 microrods 109 , and patterned lead halide perovskite microplatelets 110 . WGM lasers can also be fabricated using perovskites as quantum dots 34 .…”

“…Perovskite materials have a wide number of potential applications, including gas sensors 113 . Currently, the main problems with perovskites in WGM microlasers and sensors are their degradation in aqueous media and low photostability 108 . Some attempts to alleviate the water instability of perovskites, which mainly affects the structural and emission performance, include encapsulation in a SiO 2 shell, with the resulting composite assembled into a tubular whispering-gallery microcavity 114 .…”

Long life Perovskite Nanoplatelet Lasers with high quality factor enabled through engineering degradation pathways

“…The MAPbI 3 laser with a silica microsphere resonator could sustain by 8.6×10 6 pulses 2 . Similarly, the solution-processed FAPbBr 3 microdisk lasers could work stably for 3000 s (3×10 6 pulses) before dropping to 90% of its initial value 27 .…”