Low-dimensional perovskites are an emerging class of materials with high stability and excellent optoelectronic properties. Herein, we introduce a novel, lead-free, zero-dimensional perovskite-like material, (1,3-propanediammonium) 2 Bi 2 I 10 •2H 2 O, for optoelectronic applications. This material exhibited good moisture and thermal stability under ambient conditions. Single-crystal X-ray diffraction analysis revealed a quantum-well structure having the inorganic Bi 2 I 10 4− clusters periodically arranged in the crystallographic "c" axis separated by a distance of 5.36 Å, sandwiched by independent layers of organic cations. The density functional theory calculations showed that the oxygen in water molecules has a significant contribution to the band edges of the material. The photodetector device fabricated using this material showed an efficient charge separation at low voltage (1 V) due to the good electronic conduction between the Bi 2 I 10 4− dimer units.H ybrid perovskites have emerged as a unique semiconductor material for various optoelectronic device applications during the past few years. 1−3 Excellent properties such as long charge carrier diffusion length, low exciton binding energy, facile band gap tunability, and low-temperature solution processability made this material highly useful in these devices. 4−7 Nevertheless, poor stability under ambient conditions and toxicity of lead hampers their commercial usage. 8,9 Reports suggest that lower dimensional perovskites exhibit moisture tolerance to a great extent. 10−13 In order to address the toxicity issue, less toxic metal ions, such as Sn 2+ , Bi 3+ , Sb 3+ , and so forth, having ns 2 electrons similar to Pb 2+ were introduced into the perovskite structure. 14−16 Among them, tin-based materials are highly unstable due to the facile oxidation of the Sn 2+ to Sn 4+ state. 17 On the other hand, bismuth-and antimony-based zero-dimensional perovskites exhibited excellent moisture stability due to their rigid M 2 X 9 3−
Symmetrical electrochemical capacitors are attracting immense attention because of their fast charging–discharging ability, high energy density, and low cost of production. The current research in this area is mainly focused on exploring novel low-cost electrode materials with higher energy and power densities. In the present work, we fabricated an electrochemical double-layer capacitor using methylammonium bismuth iodide (CH 3 NH 3 ) 3 Bi 2 I 9 , a lead-free, zero-dimensional hybrid perovskite material. A maximum areal capacitance of 5.5 mF/cm 2 was obtained, and the device retained 84.8% of its initial maximum capacitance even after 10 000 charge–discharge cycles. Impedance spectroscopy measurements revealed that the active layer provides a high surface area for the electrolyte to access. As a result, the charge transport resistance is reasonably low, which is advantageous for delivering excellent performance.
CH3NH3PbBr3based luminescent perovskite nanoparticles have been used for the selective detection of an explosive, 2,4,6-trinitrophenol (picric acid) with high sensitivity in solution and vapour state.
Bismuth-based perovskite-like materials are considered as promising alternatives to lead-based perovskites for optoelectronic applications. However, the major drawbacks of these materials are high exciton binding energy and poor charge-carrier separation efficiency. These issues are attributed to the strong quantum and dielectric confinements associated with these materials. In this work, we have used a simple methodology to reduce the dielectric confinement in hybrid A3Bi2I9 type perovskite-like materials (A is an organic cation) to improve the charge-carrier separation efficiency. For that, the electronically inert methylammonium (MA) was replaced with a polarizable benzylammonium (BA) cation in the well-studied MA3Bi2I9 (MBI) structure. The single-crystal X-ray diffraction (XRD) and ultraviolet–visible (UV–vis) absorption spectroscopy analyses suggested similar quantum confinement in both (BA)3Bi2I9 (BBI) and MBI materials. This enabled us to precisely investigate the role of polarizable benzylammonium cations in the dielectric confinement in BBI. Flash-photolysis time-resolved microwave conductivity studies revealed about 2.5-fold enhancement of φ∑μ (the product of charge-carrier generation quantum yield and the sum of charge-carrier mobilities) for BBI when compared to that of MBI, which is attributed to the low dielectric confinement in the former.
Hydrophobic-capped nanocrystals of formamidinium lead bromide (FAPbBr3) perovskite (PNC) show bright and stable fluorescence in the solution and thin film states. When compared with isolated PNCs in a solution, close-packed PNCs in a thin film show extended fluorescence lifetime (ca 4.2 µs), which is due to hopping or migration of photogenerated excitons among PNCs. Both fluorescence quantum efficiency and lifetime decrease in a PNC thin film doped with C60, which is attributed to channeling of exciton migration into electron transfer to fullerenes. On the other hand, quenching of fluorescence intensity of a PNC solution isn't accompanied by any change in fluorescence lifetime, indicating static electron transfer to C60 adsorbed onto the hydrophobic surface of individual PNCs. Exciton migration among close-packed PNCs and electron transfer to C60 places C60-doped PNC thin films among cost-eff ective antenna systems for solar cells.Metal halide perovskites have emerged into a class of promising materials for top 10 future technologies such as solar cells, which is owing to their distinctive optical and electronic properties and cost-effective production. Recent reports show solar photon to electricity conversion efficiency of perovskite solar cells exceeds 20%, keeping the upper limit open to further research, which, on the other hand, hits the roof for silicon photovoltaics. 1 The commendable optical and electronic properties of perovskites make them also useful for several other optical and electronic devices such as light-emitting diodes, lasers, photodetectors, sensors and memory devices. 2 Besides the straightforward preparation and applications of perovskite films, very recently, hybrid PNCs have become popular with great research interest and technological relevance. 3 PNCs exhibit intense fluorescence due to quantum confinement effect which is easily tuned by band-gap engineering and chemical composition 4 and show great promise when compared with perovskite films. 5 Addressing fundamental photophysical properties of PNCs in combination with other materials calls for exploration, and is expected to further the applications of PNCs in LEDs and solar cells. Photoinduced electron transfer (PET) is the fundamental process in natural and artificial photosynthesis. 6 Recently, electron transfer studies in perovskite-based electron donoracceptor systems receive great momentum, which is owing to their potential application in solar cell technology. For example, Grätzel et al. revealed ultrafast electron transfer from photoexcited perovskite to mesoporous titanium dioxide, leading to efficient charge separation. 7 In a subsequent report, Sunderström et al. pinpointed the time scale and mechanism of electron transfer from perovskite to an organic acceptor molecule. 8 PNCs have been explored in electron transfer to classical acceptors such as benzoquinone, 9 phenothiazine 9 and perylene. 10 Recent studies by Huang et al. and Sargent et al. show improved stability and photocurrent response for solar cells based ...
Bismuth-based perovskites are attracting intense scientific interest due to low toxicity and excellent moisture stability compared to lead-based analogues. However, high exciton binding energy, poor charge carrier separation, and transport efficiencies lower their optoelectronic performances. To address these issues, we have integrated an electronically active organic cation, naphthalimide ethylammonium, between the [BiI 52− ] n chains via crystal engineering to form a novel perovskite-like material (naphthalimide ethylammonium) 2 BiI 5 (NBI). Single crystal analysis revealed a one-dimensional quantum-well structure for NBI in which inter-inorganic well electronic coupling is screened by organic layers. It exhibited anisotropic photoconductivity and long-lived charge carriers with milliseconds lifetime, which is higher than that of CH 3 NH 3 PbI 3 . Density functional theory calculations confirmed type-IIa band alignment between organic cations and inorganic chains, allowing the former to electronically contribute to the overall charge transport properties of the material.
The optical and electronic properties of nanoparticles/nanocrystals (NC) of methylammonium lead tribromide perovskite (MAPbBr 3 ) have been studied in detail. We observe the effect of quantum confinement in particles of an average diameter of ∼6 nm and smaller, in the form of an increase in excitonic nature with decrease in particle size. The differences in the photophysical properties in bulk and NC forms of MAPbBr 3 are clearly observed in the temperature dependent measurements, and provide insight into the length scales prevalent in this system. We demonstrate devices consisting of active layers of NC in conjunction with low band gap polymer semiconductors which exhibit the dual functionality of a light emitting diode in the forward bias and a photodetector in the reverse bias.graphic.
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