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1. Engineering Inorganic Perovskite Films by X Values of DMAPbI _x toward Large Area Photovoltaic Devices by Slot‐Die Coating

   https://doi.org/10.1002/smll.202503825  

   Qi, Yifang; Zhang, Qiqi; Aguinaga, Jeffrey; Qiu, Chuchu; Hang, Rui; He, Sheng; Upreti, Saroj; Maurya, Antim; Pradhan, Nihar; Ray, Paresh_Chandra; et al (June 2025, Small)

   Abstract Dimethylammonium lead iodide (DMAPbI_x) has the potential to address the phase stability issue of inorganic perovskite solar cells (PSCs). In this study, the crystallinity, phase structure, defect states, and crystal growth habits of DMAPbI_xare controlled by adjusting thexvalue during synthesis, where N,N‐dimethylacetamide (DMAC) is used as the solvent to regulate perovskite film growth. Furthermore, large‐area CsPbI_2.85Br_0.15perovskite films with preferred oriented growth are achieved using the optimizedxvalue in DMAPbI_xthrough the slot‐die coating method. The inorganic PSCs, with a n‐i‐p structure and the active area of 0.04 cm², achieve a champion power conversion efficiency (PCE) of 19.82%, with an open‐circuit voltage (V_oc) of 1.16 V based on perovskite films formed by slot‐die coating. This work provides important insights into the DMAPbI_x‐based method for fabricating high‐quality inorganic perovskite films, and paves the way for large‐area inorganic PSCs fabrication for practical applications. 

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2. Optical Properties of Electrochemically Gated La _{1− x} Sr _x CoO _3−δ as a Topotactic Phase‐Change Material

   https://doi.org/10.1002/adom.202300098  

   Chakraborty, Rohan_D; Postiglione, William_M; Ghosh, Supriya; Mkhoyan, K_Andre; Leighton, Chris; Ferry, Vivian_E (May 2023, Advanced Optical Materials)

   Abstract Materials with tunable infrared refractive index changes have enabled active metasurfaces for novel control of optical circuits, thermal radiation, and more. Ion‐gel‐gated epitaxial films of the perovskite cobaltite La_1−xSr_xCoO_3−δ(LSCO) with 0.00 ≤x≤ 0.70 offer a new route to significant, voltage‐tuned, nonvolatile refractive index modulation for infrared active metasurfaces, shown here through Kramers–Kronig‐consistent dispersion models, structural and electronic transport characterization, and electromagnetic simulations before and after electrochemical reduction. As‐grown perovskite films are high‐index insulators forx< 0.18 but lossy metals forx> 0.18, due to a percolation insulator‐metal transition. Positive‐voltage gating of LSCO transistors withx> 0.18 reveals a metal‐insulator transition from the metallic perovskite phase to a high‐index (n> 2.5), low‐loss insulating phase, accompanied by a perovskite to oxygen‐vacancy‐ordered brownmillerite transformation at highx. Atx< 0.18, despite nominally insulating character, the LSCO films undergo remarkable refractive index changes to another lower‐index, lower‐loss insulating perovskite state with Δn >0.6. In simulations of plasmonic metasurfaces, these metal‐insulator and insulator‐insulator transitions support significant, varied mid‐infrared reflectance modulation, thus framing electrochemically gated LSCO as a diverse library of room‐temperature phase‐change materials for applications including dynamic thermal imaging, camouflage, and optical memories. 

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3. Cesium Methylammonium Lead Iodide (Cs _x MA _1−x PbI ₃ ) Nanocrystals with Wide Range Cation Composition Tuning and Enhanced Thermal Stability of the Perovskite Phase

   https://doi.org/10.1002/anie.202306005  

   Zhang, Yangning; Aly, Omar F.; De Gorostiza, Anastacia; Shuga Aldeen, Thana; Segapeli, Allison J.; Korgel, Brian A. (June 2023, Angewandte Chemie International Edition)

   Abstract Cesium methylammonium lead iodide (Cs_xMA_1−xPbI₃) nanocrystals were obtained with a wide range of A‐site Cs‐MA compositions by post‐synthetic, room temperature cation exchange between CsPbI₃nanocrystals and MAPbI₃nanocrystals. The alloyed Cs_xMA_1−xPbI₃nanocrystals retain their photoactive perovskite phase with incorporated Cs content,x, as high as 0.74 and the expected composition‐tunable photoluminescence (PL). Excess methylammonium oleate from the reaction mixture in the MAPbI₃nanocrystal dispersions was necessary to obtain fast Cs‐MA cation exchange. The phase transformation and degradation kinetics of films of Cs_xMA_1−xPbI₃nanocrystals were measured and modeled using an Avrami expression. The transformation kinetics were significantly slower than those of the parent CsPbI₃and MAPbI₃nanocrystals, with Avrami rate constants,k, at least an order of magnitude smaller. These results affirm that A‐site cation alloying is a promising strategy for stabilizing iodide‐based perovskites. 

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4. (FA _0.83 MA _0.17 ) _0.95 Cs _0.05 Pb(I _0.83 Br _0.17 ) ₃ Perovskite Films Prepared by Solvent Volatilization for High‐Efficiency Solar Cells

   https://doi.org/10.1002/solr.202100640  

   Zhang, Qiqi; Conkle, Keonna; Ahmad, Zachary; Ray, Paresh Chandra; Kołodziejczyk, Wojciech; Hill, Glake Alton; Gu, Xiaodan; Dai, Qilin (October 2021, Solar RRL)

   Perovskite solar cells (PSCs) have attracted significant research efforts due to their remarkable performance. However, most perovskite films are prepared by the antisolvent method which is not suitable for practical applications. Herein, a (FA_0.83MA_0.17)_0.95Cs_0.05Pb(I_0.83Br_0.17)₃(CsFAMA) perovskite film fabrication technique is developed using solvent volatilization without any antisolvents. The films are formed through recrystallization via the intermediate phase CsMAFAPbI_xCl_yBr_zduring annealing, leading to high‐quality perovskite films. The perovskite growth mechanism is investigated in terms of controlling the amount of formamidinium iodide and methylammonium chloride in the precursor solutions. The oriental growth of the films via the intermediate phase is confirmed by the grazing‐incidence wide‐angle X‐ray scattering measurements. The photovoltaic properties of the perovskite films are investigated. The PSCs based on the films fabricated using the method exhibit a high efficiency of 20.6%. The method developed in this work is based on solvent volatilization, which exhibits significant potential in high reproducibility, facile operation, and large‐scale production. 

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5. Exploring the Pb _{1− x} Sr _x HfO ₃ System and Potential for High Capacitive Energy Storage Density and Efficiency

   https://doi.org/10.1002/adma.202105967  

   Acharya, Megha; Banyas, Ella; Ramesh, Maya; Jiang, Yizhe; Fernandez, Abel; Dasgupta, Arvind; Ling, Handong; Hanrahan, Brendan; Persson, Kristin; Neaton, Jeffrey_B; et al (October 2021, Advanced Materials)

   Abstract The hafnate perovskites PbHfO₃(antiferroelectric) and SrHfO₃(“potential” ferroelectric) are studied as epitaxial thin films on SrTiO₃(001) substrates with the added opportunity of observing a morphotropic phase boundary (MPB) in the Pb_1−xSr_xHfO₃system. The resulting (240)‐oriented PbHfO₃(Pba2) films exhibited antiferroelectric switching with a saturation polarization ≈53 µC cm⁻²at 1.6 MV cm⁻¹, weak‐field dielectric constant ≈186 at 298 K, and an antiferroelectric‐to‐paraelectric phase transition at ≈518 K. (002)‐oriented SrHfO₃films exhibited neither ferroelectric behavior nor evidence of a polarP4mmphase . Instead, the SrHfO₃films exhibited a weak‐field dielectric constant ≈25 at 298 K and no signs of a structural transition to a polar phase as a function of temperature (77–623 K) and electric field (–3 to 3 MV cm⁻¹). While the lack of ferroelectric order in SrHfO₃removes the potential for MPB, structural and property evolution of the Pb_1−xSr_xHfO₃(0 ≤x < 1) system is explored. Strontium alloying increased the electric‐breakdown strength (E_B) and decreased hysteresis loss, thus enhancing the capacitive energy storage density (U_r) and efficiency (η). The composition, Pb_0.5Sr_0.5HfO₃produced the best combination ofE_B = 5.12 ± 0.5 MV cm⁻¹,U_r = 77 ± 5 J cm⁻³, and η = 97 ± 2%, well out‐performing PbHfO₃and other antiferroelectric oxides. 

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