Structural Disorder and Spin Dynamics Study in Millimeter-Sized All-Inorganic Lead-Free Cesium Bismuth Halide Perovskite Single Crystals

Abstract

Perovskite single crystals have emerged as potential candidates in the field of optoelectronic devices because of their low trap state densities, long diffusion lengths, and high charge carrier mobilities. However, the presence of lead (Pb) in perovskite causes serious concerns due to lead's high-perceived toxicity and poor environmental stability. Therefore, development of lead-free perovskites as a potential alternative material and an environmentfriendly candidate has received critical attention. Here, we report the synthesis of all-inorganic millimeter-sized lead-free bismuthbased halide perovskite Cs 3 Bi 2 X 9 (X = Cl, Br, I) single crystals and their structural disorderness, optical, and spin relaxation properties in detail. Higher Urbach energy in Cs 3 Bi 2 X 9 single crystals reveals a high degree of local structural disorderness and a short range of crystallinity. We show that structural disorder affects not only the optical properties but also the magnetic and spin relaxation properties. We observe that increased structural disorder leads to enhanced smearing of local energy bands and high spin−orbit coupling. The spin relaxation time is determined in the picoseconds time scale, which corresponds to fast charge carrier dynamics. Our work provides a design strategy and in-depth understanding to develop environment-friendly lead-free and stable perovskite-based optoelectronics and spintronic devices.

Advances in Lead-Free Perovskite Single Crystals: Fundamentals and Applications

“…Our group reported the growth of Cs 3 Bi 2 Cl 9 and Cs 3 Bi 2 Br 9 SC using the slow cooling method. − In the synthesis of these crystals, cesium halide and bismuth halide precursors were mixed in DI water + acid solution and the solution was slowly cooled from 120 °C to room temperature with a controlled cooling rate. We obtained ∼6 mm sized Cs 3 Bi 2 Cl 9 crystals and ∼4 mm sized Cs 3 Bi 2 Br 9 crystals.…”

“…It results in crack-free, high-quality crystals complying with the need for retrograde solubility. The growth dynamics of crystals grown through this method have been discussed in detail by Saidaminov et al Our group has also reported the growth of Cs 3 Bi 2 I 9 crystals using the ITC method . The hydrothermal method, on the other hand, provides access to compounds otherwise difficult to synthesize under high melting points, incongruent melting, thermal strain, etc.…”

“…Furthermore, some Pb-free SCs exhibit unusual spin physics and structural disorder. Our group investigated the structural disorder and spin dynamics in all-inorganic Pb-free Cs 3 Bi 2 X 9 (X- Cl, Br, I) SCs . We find that the Cs 3 Bi 2 Br 9 system exhibits more structural disorder in comparison to Cs 3 Bi 2 Cl 9 and Cs 3 Bi 2 I 9 system.…”

Reversible Thermochromism in All‐Inorganic Lead‐Free Cs3Sb2I9 Perovskite Single Crystals

“…[1][2][3] Nevertheless, challenges relating to stability and toxicity of Pb-based perovskites have prompted researchers to explore Pb-free perovskite semiconductors. [4][5][6][7][8] To extend the photophysical performance of Pb-free perovskites, effect of external regulatory factors such as pressure, [9] temperature, [10,11] chemical doping, [8] alloying, [12] etc., are being explored. Expansion or contraction of interatomic distances caused by external factors like temperature and pressure has the potential to change the bandgap of hybrid perovskites.…”

Light‐Emitting Perovskite Solar Cells: A Tale of Two States

“…Low-cost solution-processed MHPs, in particular, have made rapid progress in solar cells (SCs), with the power conversion efficiency (PCE) reaching 25.2%. [1][2][3][4][5][6][7][8][9] Aside from photovoltaic applications, MHPs have high photoluminescence quantum efficiency (PLQY), low exciton binding energy, and high color purity, which render them an ideal candidate for the development of high-performance light-emitting diodes (LEDs). [10][11][12][13][14][15][16] Interestingly, as both perovskite LEDs and SCs have similar geometry and use the same semiconductor, therefore, perovskite light-emitting solar cells (LESCs), which can perform both functions by acting as a reversible transducer between light and electricity, hold the ultimate device architecture in the optoelectronics industry.…”