ABSTRACT
Organic diammonium cations are a promising component of both layered (2D) and conventional (3D) hybrid halide perovskites in terms of increasing the stability of perovskite solar cells (PSCs). We investigated the crystallization ability of phase-pure 2D perovskites based on 1,4-butanediammonium iodide (BDAI2) with the layer thicknesses n = 1, 2, 3 and, for the first time, revealed the presence of a persistent barrier to obtain BDA-based layered compounds with n > 1. Secondly, we introduced BDAI2 salt into 3D lead−iodide perovskites with different cation compositions and discovered a threshold-like nonmonotonic dependence of the perovskite microstructure, optoelectronic properties, and device performance on the amount of diammonium additive. The value of the threshold amount of BDAI2 was found to be ≤1%, below which bulk passivation plays the positive effect on charge carrier lifetimes, fraction of radiative recombination, and PSCs power conversion efficiencies (PCE). In contrast, the presence of any amount of diammonium salt leads to the sufficient enhancement of the photothermal stability of perovskite materials and devices, compared to the reference samples. The performance of all the passivated devices remained within the range of 50 to 80% of the initial PCE after 400 h of continuous 1 sun irradiation with a stabilized temperature of 65 °C, while the performance of the control devices deteriorated after 170 h of the experiment.
ABSTRACT
Widely spread crystal lattices of perovskites represent a natural flexible platform for chemical design of various advanced functional materials with unique features. An interplay between chemical bonding, defects and crystallochemical peculiarities makes the perovskite structure a "LEGO designer" utilizing natural features of chemical elements of the renowned Mendeleev's Periodic Table (PTE) celebrating its 150-year anniversary. In this mini-review, crystal chemistry and bonding features, physical and functional properties, preparation methods and tuning functional properties with periodicity "tools" of the PTE will be exemplified for legendary families of high-temperature superconductive cuprates, colossal magnetoresistive manganites and hybrid lead halides for a new generation of solar cells.
ABSTRACT
Solutions of methylammonium and formamidinium polyhalides (AX1+n, A = MA, FA, X = I, Br) in isopropanol are introduced as novel versatile precursors for the fabrication of APbX3 hybrid perovskite thin films via oxidation of metallic Pb. The polyhalide solution with adjustable reactivity is distributed over a metallic Pb layer followed by iodine vapor postprocessing to tune the morphology and composition of the film using only the elements inherently present in the perovskite. This method is easily reproducible in any materials science laboratory with equipment commonly used for perovskite solar cell fabrication and resulted in power conversion efficiencies of 16.2 and 17.2% for planar solar cells using MAPbI3 and MA0.25FA0.75PbI2.75Br0.25 perovskites, respectively, as a proof of concept. Implementation of metallic lead thin films as the single Pb-containing precursors reduces a number of in-lab handling hazards compared to classical PbI2 powder and solutions and provides a variety of scalable deposition options.
ABSTRACT
Despite tremendous progress in efficiency and stability, perovskite solar cells are still facing the challenge of upscaling. Here we present unique advantages of reactive polyiodide melts for solvent- and adduct-free reactionary fabrication of perovskite films exhibiting excellent quality over large areas. Our method employs a nanoscale layer of metallic Pb coated with stoichiometric amounts of CH3NH3I (MAI) or mixed CsI/MAI/NH2CHNH2I (FAI), subsequently exposed to iodine vapour. The instantly formed MAI3(L) or Cs(MA,FA)I3(L) polyiodide liquid converts the Pb layer into a pure perovskite film without byproducts or unreacted components at nearly room temperature. We demonstrate highly uniform and relatively large area MAPbI3 perovskite films, such as 100 cm2 on glass/fluorine-doped tin oxide (FTO) and 600 cm2 on flexible polyethylene terephthalate (PET)/indium tin oxide (ITO) substrates. As a proof-of-concept, we demonstrate solar cells with reverse scan power conversion efficiencies of 16.12% (planar MAPbI3), 17.18% (mesoscopic MAPbI3) and 16.89% (planar Cs0.05MA0.2FA0.75PbI3) in the standard FTO/c(m)-TiO2/perovskite/spiro-OMeTAD/Au architecture.
