perovskite and formamidine

Achieving the long-term stability of perovskite solar cells is arguably the most important challenge required to enable widespread commercialization. Understanding the perovskite crystallization process and its direct impact on device stability is critical to achieving this goal. The commonly employed dimethyl-formamide/dimethyl-sulfoxide solvent preparation method results in a poor crystal quality and microstructure of the polycrystalline perovskite films. In this work, we introduce a high-temperature dimethyl-sulfoxide-free processing method that utilizes dimethylammonium chloride as an additive to control the perovskite intermediate precursor phases. By controlling the crystallization sequence, we tune the grain size, texturing, orientation (corner-up versus face-up) and crystallinity of the formamidinium (FA)/caesium (FA)

Topics: Amidines; Cations; Dimethyl Sulfoxide; Sunlight

Herein, we investigated the stability of lead halide perovskites under ambient conditions after mixing the two cations Formamidinium (FA) and Cesium (Cs). The Cs

Topics: Amidines; Calcium Compounds; Cesium; Inorganic Chemicals

In recent years, flexible perovskite solar cells have drawn tremendous attention in the field of wearable devices, and optimization of perovskite composition plays an important role in improving film quality and photophysical properties. At present, some researchers have only studied A-site organic cations mixing or X-site halide anions mixing in the ABX

Topics: Amidines; Calcium Compounds; Carbon; Cold Temperature; Electrodes; Methylamines; Oxides; Solar Energy; Titanium

It is essential to minimize the interfacial trap states and improve the carrier collection for high efficiency perovskite solar cells (PSCs). Herein, we present a facile method to construct a p-type graded heterojunction (GHJ) in normal PSCs by deploying a gradient distribution of hole-transporting materials (poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], PTAA, in this case) in the shallow perovskite layer. The formation of the GHJ structure facilitates charge transfer and collection, and passivates interfacial trap states, thus delivering a power conversion efficiency (PCE) of 20.05 % along with steady output efficiency of 19.3 %, which is among the highest efficiencies for cesium formamidinium (Cs-FA) lead halide PSCs. Moreover, the unencapsulated devices based on these (Cs-FA) lead halide perovskites show excellent long-term stability; more than 95 % of their initial PCE can be retained after 1440 h storage under ambient conditions. This study may provide an effective strategy to fabricate high-efficiency PSCs with great stability.

Topics: Amidines; Calcium Compounds; Cations; Cesium; Electric Power Supplies; Engineering; Halogens; Lead; Oxides; Solar Energy; Titanium

Topics: Amidines; Calcium Compounds; Halogens; Lead; Magnetic Resonance Spectroscopy; Oxides; Solar Energy; Solvents; Titanium; X-Ray Diffraction

The mechanical properties of formamidinium lead halide perovskites (FAPbX

Topics: Amidines; Calcium Compounds; Crystallization; Halogens; Lead; Mechanical Phenomena; Oxides; Temperature; Titanium

Altering cation and anion ratios in perovskites has proven an excellent means of tuning the perovskite properties and enhancing the performance. Recently, methylammonium/formamidinium/cesium triple-cation mixed-halide perovskites have demonstrated efficiencies up to 22 %. Similar to the widely explored methylammonium lead halide, excess PbI

Topics: Amidines; Calcium Compounds; Cesium; Electric Power Supplies; Fluorine; Iodides; Lead; Oxides; Solar Energy; Tin Compounds; Titanium

The excellent intrinsic optoelectronic properties of methylammonium lead halide perovskites (MAPbX3, X = Br, I), such as high photoluminescence quantum efficiency, long carrier lifetime, and high gain coupled with the facile solution growth of nanowires make them promising new materials for ultralow-threshold nanowire lasers. However, their photo and thermal stabilities need to be improved for practical applications. Herein, we report a low-temperature solution growth of single crystal nanowires of formamidinium lead halide perovskites (FAPbX3) that feature red-shifted emission and better thermal stability compared to MAPbX3. We demonstrate optically pumped room-temperature near-infrared (∼820 nm) and green lasing (∼560 nm) from FAPbI3 (and MABr-stabilized FAPbI3) and FAPbBr3 nanowires with low lasing thresholds of several microjoules per square centimeter and high quality factors of about 1500-2300. More remarkably, the FAPbI3 and MABr-stabilized FAPbI3 nanowires display durable room-temperature lasing under ∼10(8) shots of sustained illumination of 402 nm pulsed laser excitation (150 fs, 250 kHz), substantially exceeding the stability of MAPbI3 (∼10(7) laser shots). We further demonstrate tunable nanowire lasers in wider wavelength region from FA-based lead halide perovskite alloys (FA,MA)PbI3 and (FA,MA)Pb(I,Br)3 through cation and anion substitutions. The results suggest that formamidinium lead halide perovskite nanostructures could be more promising and stable materials for the development of light-emitting diodes and continuous-wave lasers.

Topics: Alloys; Amidines; Calcium Compounds; Lasers; Lead; Light; Nanostructures; Nanowires; Oxides; Semiconductors; Titanium

We report on a new metal halide perovskite photovoltaic cell that exhibits both very high solar-to-electric power-conversion efficiency and intense electroluminescence. We produce the perovskite films in a single step from a solution containing a mixture of FAI, PbI2, MABr, and PbBr2 (where FA stands for formamidinium cations and MA stands for methylammonium cations). Using mesoporous TiO2 and Spiro-OMeTAD as electron- and hole-specific contacts, respectively, we fabricate perovskite solar cells that achieve a maximum power-conversion efficiency of 20.8% for a PbI2/FAI molar ratio of 1.05 in the precursor solution. Rietveld analysis of x-ray diffraction data reveals that the excess PbI2 content incorporated into such a film is about 3 weight percent. Time-resolved photoluminescence decay measurements show that the small excess of PbI2 suppresses nonradiative charge carrier recombination. This in turn augments the external electroluminescence quantum efficiency to values of about 0.5%, a record for perovskite photovoltaics approaching that of the best silicon solar cells. Correspondingly, the open-circuit photovoltage reaches 1.18 V under AM 1.5 sunlight.

Topics: Amidines; Calcium Compounds; Cations; Electric Power Supplies; Electrons; Luminescence; Oxides; Solar Energy; Solutions; Sunlight; Titanium; X-Ray Diffraction

We investigated the influence of moisture on methylammonium lead iodide perovskite (MAPbI

Topics: Amidines; Calcium Compounds; Drug Stability; Electric Power Supplies; Oxides; Solar Energy; Solvents; Steam; Titanium

Formamidinium lead triiodide (FAPbI

Topics: Amidines; Calcium Compounds; Cesium; Electric Power Supplies; Lead; Oxides; Solar Energy; Thiocyanates; Titanium

Perovskite solar cells with power conversion efficiencies exceeding 16% at AM 1.5 G one sun illumination are developed using the black polymorph of formamidnium lead iodide, HC(NH2)2 PbI3 . Compared with CH3 NH3 PbI3 , HC(NH2 )2 PbI3 extends its absoprtion to 840 nm and shows no phase transition between 296 and 423 K. Moreover, a solar cell based on HC(NH2 )2 PbI3 exhibits photostability and little I-V hysteresis.

Topics: Absorption, Physicochemical; Amidines; Calcium Compounds; Cellulose; Electric Power Supplies; Iodides; Lead; Oxides; Solar Energy; Titanium

Formamidinium (FA) lead triiodide perovskite with chlorine addition (NH2CH=NH2PbI(3-x)Clx) is employed as a light harvester in mesoscopic solar cells for the first time. It is demonstrated that a phase-pure FAPbI(3-x)Clx perovskite layer can be synthesized using a one-step solution-process at 140 °C, and the resultant solar cells deliver a maximum power conversion efficiency of 7.51%, which is the most efficient formamidinium-lead-halide perovskite mesoscopic solar cell employing a polymer hole-transporting layer. The effects of the thermal annealing temperature on the quality/morphology of the perovskite layer and the solar cells performance are discussed. The advantages offered by the one-step solution-processing method and the reduced bandgap make FAPbI(3-x)Clx perovskites an attractive choice for future hybrid photovoltaics.

Topics: Amidines; Calcium Compounds; Electric Power Supplies; Lead; Microscopy, Electron, Scanning; Oxides; Polymers; Solar Energy; Solutions; Titanium; X-Ray Diffraction