Stable Perovskite Materials Research Articles

Machine-Learning-Accelerated Perovskite Crystallization

Summary Perovskites have seen significant research interest in the last decade. As ternary and quaternary compounds, their chemical space is exceptionally large, yet perovskite development has been limited to a restricted set of chemical constituents often discovered through trial and error. Here, we report a high-throughput experimental framework for the discovery of new perovskite single crystals. We use machine learning (ML) to guide the sequence of ever-improved robotic synthetic trials. We perform high-throughput syntheses of perovskite single crystals with a protein crystallization robot and characterize the outcomes with the aid of convolutional neural network-based image recognition. We then use an ML model to predict the optimal conditions for the synthesis of a new perovskite single crystal, enabling us to report the first synthesis of (3-PLA)2PbCl4.This material exhibits strong blue emission, illustrating the applicability of the method in identifying new optoelectronic materials.

Superhydrophobic luminous nanocomposites from CsPbX3 perovskite nanocrystals encapsulated in organosilica

All-inorganic (CsPbX3, X = Cl, Br, I) perovskite nanocrystals (PNCs) demonstrate promising optoelectronic properties, provided their poor stabilities can be overcome. Herein, a facile in-situ encapsulating strategy is proposed to form super-hydrophobic nanocomposites (abbr. PNC@SSiP) on a large scale by incorporating CsPbBr3 NCs into organosilica nanoparticles, which reduces degradation and improves the environmental stabilities. The resulting nanocomposites demonstrated monodispersed CsPbBr3 NCs (5–6 nm) embedded homogeneously in the organosilica matrix, and a high photoluminescence quantum yield (PLQY over 50%). The PNC@SSiP exhibited extraordinary stability towards water, enhanced thermal stability and photostability. However, photoluminescent (PL) decay of less than 20% can be monitored if the PNC@SSiP nanocomposites are immersed in water for 60 days. In addition, a high static contact angle for water (152.44 ± 0.97°) further indicates excellent super-hydrophobicity of the nanocomposites. The super-hydrophobic PNC@SSiP nanocomposites can be used for fabricating luminous devices, such as white light emitting diode (WLED), further demonstrating the potential value of the obtained nanocomposites as a stable luminophore in optoelectronic applications. This novel synthesis strategy greatly widens the methods for fabricating highly stable perovskite materials in optoelectronic applications.

Triamine‐Based Aromatic Cation as a Novel Stabilizer for Efficient Perovskite Solar Cells

AbstractOperational stability of perovskite solar cells has been a challenge from the beginning of perovskite research. In general, humidity and heat are the most well‐known degradation sources for perovskites, requiring ideal design of perovskite chemistry to withstand them. Although triple‐cation perovskite (Cs0.05(FA0.85MA0.15)0.95Pb(I0.85Br0.15)3) has been already introduced as the stable perovskite material, the high reactivity of methylammonium and formamidinium in the cation sites demands further modification. Herein, 1,2,4‐triazole is suggested as an effective cation solute to improve the performance and stability of perovskite solar cells. 1,2,4‐Triazole is an aromatic cation with low dipole moment that is stable under humidity and heat. It also possesses three nitrogen atoms, forming additional hydrogen bonds in the lattice, stabilizing the material. In this study, the solar cell utilizing 1,2,4‐triazole alloying achieves a power conversion efficiency of 20.9% with superior stability under extreme condition (85 °C/85% of relative humidity (RH), encapsulated) for 700 h. The 1,2,4‐triazole‐alloyed perovskite exhibits reduced trap density and film roughness and enhanced carrier lifetime with electrical conductivity, suggesting an ideal perovskite structure for efficient and stable optoelectronic applications.

Unraveling the Impact of Halide Mixing on Perovskite Stability.

Increasing the stability of perovskites is essential for their integration in commercial photovoltaic devices. Halide mixing is suggested as a powerful strategy toward stable perovskite materials. However, the stabilizing effect of the halides critically depends on their distribution in the mixed compound, a topic that is currently under intense debate. Here we successfully determine the exact location of the I and Cl anions in the CH3NH3PbBr3–yIy and CH3NH3PbBr3–zClz mixed halide perovskite lattices and correlate it with the enhanced stability we find for the latter. By combining scanning tunneling microscopy and density functional theory, we predict that, for low ratios, iodine and chlorine incorporation have different effects on the electronic properties and stability of the CH3NH3PbBr3 perovskite material. In addition, we determine the optimal Cl incorporation ratio for stability increase without detrimental band gap modification, providing an important direction for the fabrication of stable perovskite devices. The increased material stability induced by chlorine incorporation is verified by performing photoelectron spectroscopy on a half-cell device architecture. Our findings provide an answer to the current debate on halide incorporation and demonstrate their direct influence on device stability.

Bifunctional Organic Spacers for Formamidinium-Based Hybrid Dion-Jacobson Two-Dimensional Perovskite Solar Cells.

Three-dimensional (3D) perovskite materials display remarkable potential in photovoltaics owing to their superior solar-to-electric power conversion efficiency, with current efforts focused on improving stability. Two-dimensional (2D) perovskite analogues feature greater stability toward environmental factors, such as moisture, owing to a hydrophobic organic cation that acts as a spacer between the inorganic layers, which offers a significant advantage over their comparatively less stable 3D analogues. Here, we demonstrate the first example of a formamidinium (FA) containing Dion-Jacobson 2D perovskite material characterized by the BFA n-1Pb nI3 n+1 formulation through employing a novel bifunctional organic spacer (B), namely 1,4-phenylenedimethanammonium (PDMA). We achieve remarkable efficiencies exceeding 7% for (PDMA)FA2Pb3I10 based 2D perovskite solar cells resisting degradation when exposed to humid ambient air, which opens up new avenues in the design of stable perovskite materials.

Binary metal zinc-lead perovskite built-in air ambient: Towards lead-less and stable perovskite materials

Organo-metal halide perovskites are promising new-generation photovoltaic materials owing to their efficient electrical/optical characteristics. Despite having high efficiency, perovskites are toxic due to the presence of lead and instable in air ambient. Therefore, the toxicity and instability call for more efforts in this area. Here, methylammonium-zinc-lead iodide (MAZn0.2Pb0.8I3) is synthesized in air ambient as lead-less and more stable perovskite material for applying as the active layer of solar cells. 1.65 eV optical band gap and 51 nm minority carrier diffusion length (Ldiff) have been obtained with the help of UV–Visible spectroscopy (UV–Vis) and steady-state photocarrier grating (SSPG) technique respectively. Structural, chemical bonding and surface studies are done by X-ray powder diffraction (XRPD), Fourier-transform infrared spectroscopy (FTIR) and Field Emission Scanning Electron Microscope (FESEM) respectively. The sample has been stored in dark air ambient with average relative humidity of 45% at room temperature (27 °C) for 60 days and the properties of 60 days aged sample is investigated and compared with characteristics of 60 days aged MAPbI3. The results confirm MAZn0.2Pb0.8I3 is more stable than MAPbI3.

Cs0.15FA0.85PbI3 perovskite solar cells for concentrator photovoltaic applications

Recently developed, highly stable perovskite materials show promise for use in concentrator photovoltaics where the illumination intensity far exceeds standard test conditions.

An all perovskite direct methanol solid oxide fuel cell with high resistance to carbon formation at the anode

A chemically stable perovskite material Sr2Fe1.5Mo0.5O6 (SFMO) is employed as the anode of a solid oxide fuel cell (SOFC). An electrolyte-supported single cell with anode, electrolyte and cathode all made of perovskite structured materials and with a configuration of SFMO|La0.8Sr0.2Ga0.83Mg0.17O3|Ba0.5Sr0.5Co0.8Fe0.2O3 (SFM|LSGM|BSCF) is fabricated by a screen printing method. The single cell gives a maximum power density of 391 mW cm−2 for CH3OH, and 520 mW cm−2 for H2 as the fuel, respectively, at 1073 K with oxygen as the oxidant gas. The mass spectra of the flue gas out of the test reactor confirm that methanol thermally decomposes inside the anode chamber and generates mainly CO and H2 at 1023 K. Analysis of the after-test cell tells that the anode surface has no carbon formation under reaction with methanol as the feed for 3 h. The carbon resistance is attributed to the fact that the anode is in oxide state which cannot facilitate the formation of bulk carbon with graphite structure. The fast activation and gasification of the carbon species by the oxidative atmosphere around the anode surface are also beneficial factors. The test results indicate also that the activation of CH3OH is much more difficult than that of H2.