Solution‐Processed Faraday Rotators Using Single Crystal Lead Halide Perovskites

Lead halide perovskites (LHPs) have become a promising alternative for a wide range of optoelectronic devices, thanks to their solution‐processability and impressive optical and electrical properties. More recently, LHPs have been investigated in magneto‐optic studies and have exhibited spin‐polarized emission, photoinduced magnetization, and long spin lifetimes. Here, the viability of methylammonium lead bromide (MAPbBr(3)) single crystals as solution‐processed Faraday rotators is demonstrated. Compared to terbium gallium garnet, the industry standard in the visible, it is found that MAPbBr(3) exhibits Verdet constants (i.e., strength of Faraday effect) of similar or greater magnitude (up to 2.5x higher), with lower temperature dependence. Due to its low trap absorption, it is calculated that an optical isolator made from MAPbBr(3), with appropriate antireflection coatings, should reach ≈95% transmission and achieve 40 dB isolation for incoming powers of over 2 W. It is also shown that the Verdet constant of MAPbBr(3) can be calculated accurately from its dispersion in refractive index, allowing the possibility to predict similar effects in other perovskite materials.