Photovoltaic & Optoelectronic Device Group

Abstract:

Owing to the unique chemical and electronic properties arising from 3d‐electrons, substitution with transition metal ions is one of the key routes for engineering new functionalities into materials. While this approach has been used extensively in complex metal oxide perovskites, metal halide perovskites have largely resisted facile isovalent substitution. In this work, it is demonstrated that the substitution of Co2+ into the lattice of methylammonium lead triiodide imparts magnetic behavior to the material while maintaining photovoltaic performance at low concentrations. In addition to comprehensively characterizing its magnetic properties, the Co2+ ions themselves are utilized as probes to sense the local electronic environment of Pb in the perovskite, thereby revealing the nature of their incorporation into the material. A comprehensive understanding of the effect of transition metal incorporation is provided, thereby opening the substitution gateway for developing novel functional perovskite materials and devices for future technologies.

Abstract:

Wide-coverage near infrared (NIR) phosphor-converted LEDs possess promising potential for practical applications, but little is developed towards the efficient and wide-coverage NIR phosphors. Here, we report the single-component lanthanide (Ln³⁺ ) ions doped Cs₂ M(In_0.95 Sb_0.05 )Cl₆ (M=alkali metal) nanocrystals (NCs), exhibiting emission from 850 to 1650 nm with high photoluminescence quantum yield of 20.3 %, which is accomplished by shaping the multiple metal halide octahedra of double perovskite via the simple alkali metal substitution. From Judd-Ofelt theoretical calculation and spectroscopic investigations, the shaping of metal halide octahedra in Cs₂ M(In_1-x Sb_x )Cl₆ NCs can break the forbidden of f-f transition of Ln³⁺ , thus increasing their radiative transition rates and simultaneously boosting the energy transfer efficiency from host to Ln³⁺ . Finally, the wide-coverage NIR LEDs based on Sm³⁺ , Nd³⁺ , Er³⁺ -tridoped Cs₂ K_0.5 Rb_0.5 (In_0.95 Sb_0.05 )Cl₆ NCs are fabricated and employed in the multiplex gas sensing and night-vision application.