Two-Step Synthesis of Bismuth-Based Hybrid Halide Perovskite Thin-Films

Bismuth-Based Perovskite Derivates with Thermal Voltage Exceeding 40 mV/K

Heat is an inexhaustible source of energy, and it can be exploited by thermoelectronics to produce electrical power or electrical responses. The search for a low-cost thermoelectric material that could achieve high efficiencies and can also be straightforwardly scalable has turned significant attention to the halide perovskite family. Here, we report the thermal voltage response of bismuth-based perovskite derivates and suggest a path to increase the electrical conductivity by applying chalcogenide doping. The films were produced by drop-casting or spin coating, and sulfur was introduced in the precursor solution using bismuth triethylxanthate. The physical-chemical analysis confirms the substitution. The sulfur introduction caused resistivity reduction by 2 orders of magnitude, and the thermal voltage exceeded 40 mV K-1 near 300 K in doped and undoped bismuth-based perovskite derivates. X-ray diffraction, Raman spectroscopy, and grazing-incidence wide-angle X-ray scattering were employed to confirm the structure. X-ray photoelectron spectroscopy, elemental analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were employed to study the composition and morphology of the produced thin films. UV-visible absorbance, photoluminescence, inverse photoemission, and ultraviolet photoelectron spectroscopies have been used to investigate the energy band gap.

Eco-friendly MA3Bi2I9perovskite thin films based ammonia sensor

Organic-inorganic perovskite halides (OIPH) have emerged as a wonder material with growing interest in sensors detecting various toxic gases. However, lead toxicity represents a potential obstacle, and therefore finding lead-free cost-effective compatible materials for gas sensing applications is essential. In this work, methylammonium bismuth iodide i.e. (CH₃NH₃)₃Bi₂I₉(MABI) perovskite thin films-based ammonia (NH₃) sensor was synthesized using an antisolvent-assisted one-step spin coating method. The MABI sensor shows a linear relationship between the responsivity and concentration of NH₃with excellent reversibility, high gas responsivity, and humidity stability. The MABI thin-film sensor exhibits a maximum gas response of 24%, a short response/recovery time i.e. 0.14 s /8.15 s and good reversibility at 6 ppm of NH₃. It was observed that MABI thin films based sensors have excellent ambient stability over a couple of months. This work reveals that it is feasible to design high-performance gas sensors based on environmentally-friendly Bi-based OIPH materials.

A Critical Review of the Use of Bismuth Halide Perovskites for CO2 Photoreduction: Stability Challenges and Strategies Implemented

Inspired by natural photosynthesis, the photocatalytic CO2 reduction reaction (CO2RR) stands as a viable strategy for the production of solar fuels to mitigate the high dependence on highly polluting fossil fuels, as well as to decrease the CO2 concentration in the atmosphere. The design of photocatalytic materials is crucial to ensure high efficiency of the CO2RR process. So far, perovskite materials have shown high efficiency and selectivity in CO2RR to generate different solar fuels. Particularly, bismuth halide perovskites have gained much attention due to their higher absorption coefficients, their more efficient charge transfer (compared to oxide perovskites), and their required thermodynamic potential for CO2RR. Moreover, these materials represent a promising alternative to the highly polluting lead halide perovskites. However, despite all the remarkable advantages of bismuth halide perovskites, their use has been limited, owing to instability concerns. As a consequence, recent reports have offered solutions to obtain structures highly stable against oxygen, water, and light, promoting the formation of solar fuels with promising efficiency for CO2RR. Thus, this review analyzes the current state of the art in this field, particularly studies about stability strategies from intrinsic and extrinsic standpoints. Lastly, we discuss the challenges and opportunities in designing stable bismuth halide perovskites, which open new opportunities for scaling up the CO2RR.