Concept: Lead(II) iodide
For the first time, micro/nano-sized lead iodide hydroxide; Pb(OH)I, has been successfully prepared via a simple ultrasonic method. In this method, lead nitrate and lithium iodide were applied as starting reagents to fabricate Pb(OH)I micro/nanostructures at different conditions. The effect of different surfactants like N,N-bis(salicylidene)-ethylenediamine (H2salen), sodium dodecyl sulfate (SDS) and polyvinylpyrrolidone (PVP), sonication time, and ultrasonic intensity on the morphology and particle size of the products has been investigated. The as-produced micro/nanostructures were characterized with the aid of XRD, SEM, TEM, UV-vis, EDS and FT-IR. According to the SEM images, different morphologies of Pb(OH)I including micro- and nano-sized rods were formed by changing the preparation conditions. Based on the XRD results, it was found that Pb(OH)I and PbI2 have been produced with and without sonication at the same conditions, respectively. The use of the H2salen and sonication treatment were confirmed to be the crucial factors determining the formation of one-dimensional Pb(OH)I micro/nanostructures.
A mixed halide perovskite of CH3NH3PbI3-xClx is synthesized via two-step sequential solution deposition by using a mixture of PbCl2 and PbI2 as the precursor to overcome the low solubility of pure PbCl2 with easy morphology control. 11.7% power conversion efficiency is achieved for the mesoscopic cell, much higher than the cell constructed via a spin-coating process.
We study the impact of excitation energy on the photostability of methylammonium lead triiodide (CH3NH3PbI3or MAPI) perovskite thin films. Light soaking leads to a transient increase of the photoluminescence efficiency at excitation wavelengths longer than 520 nm while light-induced degradation occurs when exciting the films with wavelengths shorter than 520 nm. X-ray diffraction and extinction measurements reveal the light-induced decomposition of CH3NH3PbI3to lead iodide (PbI2) for the high energy excitation regime. We propose a model explaining the energy dependence of the photostability, involving the photoexcitation of residual PbI2species in the perovskite triggering the decomposition of CH3NH3PbI3.
Halide perovskite derivatives present unprecedented physical phenomena among those materials which are suitable for photovoltaics, such as a fast ion diffusion coefficient. In this paper it is reported how the benefits of this property can be used during the growth of halide perovskites in order to control the morphological and optoelectronic properties of the final thin film. Using a large enough halide reservoir, the nature of the halides present in the final perovskite layer can be exchanged and this depends on the initial salt used in the two-step deposition method. In particular, the preparation of a methylammonium lead bromide (MAPbBr3) thin film is reported, using a two-step method based on the transformation of lead(ii) iodide (PbI2), lead(ii) bromide (PbBr2) and lead(ii) chloride (PbCl2) salts into MAPbBr3 perovskite after dipping in a methylammonium bromide (MABr) solution. The films prepared from different salts present different properties in terms of morphology and optoelectronic properties, thus providing significantly different performance when they are used for the preparation of photovoltaic devices. Interestingly, the use of PbI2 and PbCl2 salts reduce the charge recombination and increase the open circuit potential obtained, especially in the former case. However, the highest photocurrent is obtained when PbBr2 is used. For PbI2 and PbCl2 salts no traces of the former salt are observed in the MAPbBr3 layer obtained after 10 minutes of dipping time, however, the presence of PbBr2 has still been detected (using X-ray diffraction) when this salt has been employed.
A novel, aqueous precursor system (Pb(NO3)2 + water) is developed to replace conventional (PbI2 + DMF) for fabricating methylammonium lead iodide (MAPbI3) perovskite solar cells (PSCs). When the morphology and surface coverage of the Pb(NO3)2 film was controlled during coating, a power conversion efficiency of 12.58% under standard conditions (AM1.5, 100 mW cm(-2)) was achieved for the PSC.
An individual layer of lead iodide (depicted in the lower part of the image) is seamlessly wrapped into a cylinder, resulting in the formation of a single-walled inorganic nanotube. To achive this, a solvent-free high-temperature route is employed using the inner cavities of multiwalled carbon nanotubes as hosting templates. This work is described by G. Tobias and co-workers on page 2016.
The template assisted growth of single-layered inorganic nanotubes is reported. Single-crystalline lead iodide single-layered nanotubes have been prepared using the inner cavities of carbon nanotubes as hosting templates. The diameter of the resulting inorganic nanotubes is merely dependent on the diameter of the host. This facile method is highly versatile opening up new horizons in the preparation of single-layered nanostructures.