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Impact of rationally selected additives in precursor solutions on the nucleation and growth of hybrid perovskite thin films is investigated.
New perovskites are formed by introducing polyatomic yet aprotic superalkali species at the cationic A-sites of the ABX 3 structure.
There has been considerable speculation over the nature of charge carriers in organic–inorganic hybrid perovskites, i.e., whether they are free and band-like, or they are prone to self-trapping via short range deformation potentials. Unusually long minority-carrier diffusion lengths and moderate-to-low mobilities, together with relatively few deep defects add to their intrigue. Here we implement density functional methods to investigate the room-temperature, tetragonal phase of CH 3 NH 3 PbI 3 . We compare charge localization behavior at shallow levels and associated lattice relaxation versus those at deep polaronic states. The shallow level originates from screened Coulomb interaction between the perturbed host and an excited electron or hole. The host lattice has a tendency towards forming these shallow traps where the electron or hole is localized not too far from the band edge. In contrast, there is a considerable potential barrier that must be overcome in order to initiate polaronic hole trapping. The formation of a hole polaron (I 2 - center) involves strong lattice relaxation, including large off-center displacement of the organic cation, CH 3 NH 3 + . This type of deep polaron is energetically unfavorable, and active shallow traps are expected to shape the carrier dynamics in this material.
Cyclodextrin macrocycles are able to modify and control the solvation equilibria of hybrid perovskite components in solution by establishing supramolecular interactions.
The adsorption kinetics of CO 2 was experimentally characterized in ultra-high vacuum (UHV). In addition, density functional theory (DFT) calculations were included.
Trinuclear cobalt paddlewheel complexes, [Co 3 (dpa) 4 X 2 ] (dpa = the anion of 2,2'-dipyridylamine, X = Cl–, Br–, –NCS–, –CN–, (NC) 2 N–), are known to demonstrate a thermally-induced spin-crossover (SCO). Despite a wealth of structural and magnetic information about such complexes, the role of the axial ligand on the characteristic SCO temperature (T 1/2 ) remains ambiguous. The situation is complicated by the observation that the solid state geometry of the complexes, symmetric or unsymmetric, with respect to the central cobalt ion, also appears to influence the SCO behavior. In order to seek trends in the relationship between the nature of the axial ligand, geometry and magnetic properties, we have prepared the first examples of tricobalt paddlewheel complexes with axial fluorido and iodido ligands, as well as two new chlorido and bromido solvates. Their SCO properties are discussed in the context of an examination of previously reported chlorido and bromido adducts. The main conclusions are: (1) T 1/2 values follow the trend I– < Br– ≈ Cl– < F–; (2) while the molecular geometry is predominantly guided by crystal packing for the Cl–, Br– and I– derivatives, the presence of an axial fluoride may favor a more symmetric core; (3) the magnetic characterization of a second example of an unsymmetric complex supports the observation that they display dramatically lower T 1/2 values than their symmetric analogues; and (4) SCO in crystallographically symmetric compounds apparently occurs without loss of molecular or crystallographic symmetry, while a gradual geometric transformation linking the temperature dependence of quasi-symmetric to unsymmetric in crystallographically unconstrained compounds was found.
Our mass spectrometry measurements indicate that the hot-carrier-induced deprotonation of MA + cations is the fundamental origin of photodegradation.
Here, whe conversion mechanism from the precursor ink to the perovskite film using antisolvent-induced crystallization has been studied using in situ X-ray diffraction during blade coating and antisolvent deposition. We study various solvent systems forming methylammonium lead iodide perovskite. We find that it is critical to add the antisolvent before the formation of a crystalline intermediate phase. Compared to thermal crystallization, the antisolvent-induced crystallization alters the conversion route. Instead of heterogeneous nucleation and conversion through a crystalline intermediate phase, antisolvent-assisted annealing leads to a rapid direct crystallization, resulting in highly regular smooth films.
Abstract not provided
Explaining most known double perovskite electronic structures and predicting new ones using Linear Combination of Atomic Orbitals analysis.
Experimental and theoretical study on the effect of shallow and deep defects on photovoltaic performance, luminescence, surface photovoltage, and density of states.
Changes in perovskite structural dimensionality brought by mixing A-site cations play an important role in determining the measured charge carrier mobility, and in the solar cell performance.
Are classical nucleation theory and the 1950 LaMer model of particle formation supported for a wide range of particle formations, or do competing models in the form of chemical reaction mechanisms have better experimental support? Read on to find out.
Non-chiral orthorhombic perovskite nanostructures can exhibit chiro-optic effects under off-normal illumination due to the Rashba effect.
Using branched spacer cations results in a modulated rippled 2D perovskite structure and materials for solar cells.
This Perspective features the newly emerged AIO-type Cu( i )X-based hybrid semiconductors and showcases their structural diversity, solution-processability, framework stability, important photophysical properties and related potential applications.
With in situ ESEM and GIWAXS we saw that the perovskite degradation passes through hexagonal polytypes and is dependent on the composition.
Lone-pair covalency can faciliate dynamic tilting of MBr 6 octahedra and increase dynamic structural instabilities.