Search

As promising photovoltaic materials, halide perovskites display large structural modifiability specific to their organic‐inorganic hybrid lattices, thus providing key to unlock many enhanced and novel physical properties. In particular, hybrid perovskites exhibit extraordinary functional responses to mechanical stimulation due to their soft lattices. However, a general pattern describing the evolution of perovskite properties under pressure is missing, rendering such research without theoretical guidance and further the optimization of optoelectronic performance. Here, a framework delineating the pressure‐dependent evolutions of lattice structure, bandgap, and photoluminescence (PL) across four distinct regions in all perovskites assuming 3D and 2D structures is unveiled, accrediting long‐range disorderness to be the common origin of bandgap blueshift, PL annihilation, and structural amorphization. Using such developed model as an instructional guideline, an optical bandgap and luminescent evolutions in quasi‐2D tin(II) iodide perovskites are revealed, where (C4H9NH3)2(CH3NH3)Sn2I7 (C4H9NH3+: butylammonium; CH3NH3+: methylammonium) is found to be the softest perovskite (bulk modulus ≈4.8 GPa) known so far. By meticulously choosing appropriate peak pressure ≈4 GPa, (C4H9NH3)2(CH3NH3)Sn2I7 shows irreversible defect healing (carrier lifetime prolongation from 7 to 22 ns) and permanent PL enhancement upon decompression to ambient condition, signifying practicality of the pressure‐driven behaviors unveiled in this work. [ABSTRACT FROM AUTHOR]

The precise, controllable, and safe application of pesticides can effectively reduce pesticide consumption and minimize chemical pollution at the source. Here, a light‐responsive controlled‐release system with flexible control, precise release, easy recovery, and suitability for future pesticide application in aquatic environments is proposed. The system precisely controls the release of pesticides through a light‐responsive composite nanochannel membrane (CTC@SNM/PET) with reactive coumarin derivatives (CTC) as gating molecules. The prepared nanochannel membrane has an ultrathin thickness of 67.5 nm and well‐ordered vertical nanochannels with a uniform size of 1.9 nm, providing a prerequisite for precise molecular gating and high permeability for mass transport. CTC monomers can realize cycloaddition/cyclocracking and nanochannel closing/opening to control the release of pesticides by controlling 365/254 nm ultraviolet light irradiation. As a proof of concept, the light‐responsive controlled‐release system based on CTC@MSF/PET against Saprolegnia parasitica achieves an inhibition rate of more than 95% and reduces pesticide residues by 56.5% compared to the control group. The proposed membrane system has great application potential to easily enable remote, quantitative, timed, and positioned pesticide application, thereby reducing pesticide residues and providing a prospective approach to reducing environmental and human risks. [ABSTRACT FROM AUTHOR]

The soft nature of organic–inorganic halide perovskites renders their lattice particularly tunable to external stimuli such as pressure, undoubtedly offering an effective way to modify their structure for extraordinary optoelectronic properties. Here, using the methylammonium lead iodide as a representative exploratory platform, it is observed that the pressure‐driven lattice disorder can be significantly suppressed via hydrogen isotope effect, which is crucial for better optical and mechanical properties previously unattainable. By a comprehensive in situ neutron/synchrotron‐based analysis and optical characterizations, a remarkable photoluminescence (PL) enhancement by threefold is convinced in deuterated CD3ND3PbI3, which also shows much greater structural robustness with retainable PL after high peak‐pressure compression–decompression cycle. With the first‐principles calculations, an atomic level understanding of the strong correlation among the organic sublattice and lead iodide octahedral framework and structural photonics is proposed, where the less dynamic CD3ND3+ cations are vital to maintain the long‐range crystalline order through steric and Coulombic interactions. These results also show that CD3ND3PbI3‐based solar cell has comparable photovoltaic performance as CH3NH3PbI3‐based device but exhibits considerably slower degradation behavior, thus representing a paradigm by suggesting isotope‐functionalized perovskite materials for better materials‐by‐design and more stable photovoltaic application. [ABSTRACT FROM AUTHOR]

Bond length and bond angle exhibited by valence electrons is essential to the core of chemistry. Using lead-based organic-inorganic perovskite compounds as an exploratory platform, it is demonstrated that the modulation of valence electrons by compression can lead to discovery of new properties of known compounds. Yet, despite its unprecedented progress, further efficiency boost of lead-based organic-inorganic perovskite solar cells is hampered by their wider bandgap than the optimum value according to the Shockley-Queisser limit. By modulating the valence electron wavefunction with modest hydraulic pressure up to 2.1 GPa, the optimized bandgap for single-junction solar cells in lead-based perovskites, for the first time, is achieved by narrowing the bandgap of formamidinium lead triiodide (HC(NH2)2PbI3) from 1.489 to 1.337 eV. Strikingly, such bandgap narrowing is partially retained after the release of pressure to ambient, and the bandgap narrowing is also accompanied with double-prolonged carrier lifetime. With First-principles simulation, this work opens a new dimension in basic chemical understanding of structural photonics and electronics and paves an alternative pathway toward better photovoltaic materials-by-design. [ABSTRACT FROM AUTHOR]