Halide-based Perovskite Research Articles

Vacuum-assisted thermal annealing of CH3NH3PbI3 for highly stable and efficient perovskite solar cells.

Solar cells incorporating lead halide-based perovskite absorbers can exhibit impressive power conversion efficiencies (PCEs), recently surpassing 15%. Despite rapid developments, achieving precise control over the morphologies of the perovskite films (minimizing pore formation) and enhanced stability and reproducibility of the devices remain challenging, both of which are necessary for further advancements. Here we demonstrate vacuum-assisted thermal annealing as an effective means for controlling the composition and morphology of the CH(3)NH(3)PbI(3) films formed from the precursors of PbCl(2) and CH(3)NH(3)I. We identify the critical role played by the byproduct of CH(3)NH(3)Cl on the formation and the photovoltaic performance of the perovskite film. By completely removing the byproduct through our vacuum-assisted thermal annealing approach, we are able to produce pure, pore-free planar CH(3)NH(3)PbI(3) films with high PCE reaching 14.5% in solar cell device. Importantly, the removal of CH(3)NH(3)Cl significantly improves the device stability and reproducibility with a standard deviation of only 0.92% in PCE as well as strongly reducing the photocurrent hysteresis.

Elucidating the charge carrier separation and working mechanism of CH3NH3PbI3−xClx perovskite solar cells

Developments in organic-inorganic lead halide-based perovskite solar cells have been meteoric over the last 2 years, with small-area efficiencies surpassing 15%. We address the fundamental issue of how these cells work by applying a scanning electron microscopy-based technique to cell cross-sections. By mapping the variation in efficiency of charge separation and collection in the cross-sections, we show the presence of two prime high efficiency locations, one at/near the absorber/hole-blocking-layer, and the second at/near the absorber/electron-blocking-layer interfaces, with the former more pronounced. This 'twin-peaks' profile is characteristic of a p-i-n solar cell, with a layer of low-doped, high electronic quality semiconductor, between a p- and an n-layer. If the electron blocker is replaced by a gold contact, only a heterojunction at the absorber/hole-blocking interface remains.

CH3NH3SnxPb(1-x)I3 Perovskite Solar Cells Covering up to 1060 nm.

We report photovoltaic performances of all-solid state Sn/Pb halide-based perovskite solar cells. The cell has the following composition: F-doped SnO2 layered glass/compact titania layer/porous titania layer/CH3NH3SnxPb(1-x)I3/regioregular poly(3-hexylthiophene-2,5-diyl). Sn halide perovskite itself did not show photovoltaic properties. Photovoltaic properties were observed when PbI2 was added in SnI2. The best performance was obtained by using CH3NH3Sn0.5Pb0.5I3 perovskite. 4.18% efficiency with open circuit voltage 0.42 V, fill factor 0.50, and short circuit current 20.04 mA/cm(2) are reported. The edge of the incident photon to current efficiency curve reached 1060 nm, which was 260 nm red-shifted compared with that of CH3NH3PbI3 perovskite solar cells.

Optimization of Langmuir-Blodgett Film Formation for Organic-Inorganic Layer Perovskite by Squeeze out Method

In order to obtain the uniform film having well-defined lead halide-based layer perovskite structure, we proposed squeezed opt method. It is found that the optimized condition with respect to docosylammonium bromide is revealed by employing hexadecylammonium bromide among tetradecylammonium bromide, hexadecylammonium bromide and octadecylammonium bromide.

Orientation of azobenzene chromophore incorporated into metal halide-based layered perovskite having organic–inorganic superlattice structure

Thin films of cadmium bromide-based layered perovskites with a superlattice structure consisting of an inorganic layer of corner-sharing CdBr 6 octahedra and an organic layer of azobenzene-linked ammonium molecules were prepared by spin-coating from dimethylformamide solutions in which CdBr 2 and azobenzene-linked ammonium bromides were dissolved. In the layered perovskite films, azobenzene chromophore was demonstrated to have a tendency to be oriented nearly normal to the film plane from the linear dichroism measurement. In addition, the relationship between orientational order (order parameter and tilt angle) of azobenzene chromophore and molecular structure of the azobenzene-linked ammonium molecules was investigated.

Crystal Structure and Properties of Dye-Containing Organic-Inorganic Perovskites

The oligothiophene derivative, 5,5′′′-bis(aminoethyl) 2,2′:5′,2′′:5′′, 2′′′-quaterthiophene (AEQT), has been incorporated within a lead(II) halide-based perovskite framework. Single crystal X-ray analysis has been used to verify the perovskite framework and examine the ordering of the dye cations within the structure. Thin films of (AEQT)PbX4 (X = Cl, Br, and I) have also been thermally ablated onto quartz substrates and the optical properties of the films have been examined. Strong photoluminescence from the quaterthiophene moiety is observed for X = Cl, with an emission peak at approximately λmax = 532 nm. Similar photoluminescence is observed for the X = Br and I materials, but with progressively less intensity, as the band gap of the inorganic framework gets smaller relative to the LUMO-HOMO gap of the dye molecule. (AEQT)PbCl4 films have also been incorporated as emission layers in light emitting devices (LED) and intense room temperature electroluminescence has been observed.

Self-organization approach to organic/inorganic quantum-well based on metal halide-based layer perovskite

We report here two topics on the construction of organic/inorganic quantum-well materials based on metal halide-based layer perovskite having an alternate layer structure consisting of an organic ammonium layer and a metal halide semiconductor layer. The first topic is the construction of new organic/inorganic quantum-well materials incorporated with functionalized ammonium molecules, which possess chromophores such as naphthalene and azobenzene, as an organic layer. In the second topic, we demonstrate a new method for the preparation of metal halide-based layer perovskite quantum-wells by using intercalation of organic ammonium molecules.

Molecular dynamics simulation of superionicity in Neighborite, NaMgF3

Superionicity in neighborite, NaMgF3, has been studied by molecular dynamics using parameter‐free Gordon‐Kim potentials. These simulations show that this halide‐based perovskite has a superionic phase. The onset temperature for superionicity is ∼ 50–100 K below the melting point. This is a novel type of superionicity in a halide, occurring as it does in a perovskite rather than a fluorite. Superionicity is demonstrated to occur whether one uses the full ionicity for Mg2+ and F− or employs reduced charges derived from a Quantum Chemistry calculation. The relevance of these findings to predictions of superionicity in the oxide perovskite MgSiO3[Matsui and Price, 1991] is discussed.