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Manipulating the Phase Distributions and Carrier Transfers in Hybrid Quasi-Two-Dimensional Perovskite Films
摘要： Quasi two-dimensional perovskites are promising alternatives to conventional three-dimensional perovskites because of their high stability and easy tunability. However, controlling the phase distribution according to device architecture remains a major challenge. Here, the manipulation of phase purity and vertical distribution proven by ultrafast transient absorption spectroscopy, and their effect on device characteristics are reported. By adding ethyl acetate as antisolvent, the growth direction of the perovskite film is flipped. CH3NH3Cl and dimethyl sulfoxide are used to slow the growth rate of the crystal, which gives better phase purity. The direction of carrier transfer is tuned accordingly. It is found that solar cell performance is more sensitive to phase purity relative to vertical distribution. These findings are of importance for the applications of quasi-2D perovskites in different types of devices that require to change phase purity and vertical distribution.
关键词： solar cells,carrier transfer,vertical distribution,phase purity,quasi-2D perovskite
更新于2025-11-19 16:56:35
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A facile route for synthesis of highly pure α-CaB4O7 compound
摘要： In this study, a facile route was developed for the synthesis of α-CaB4O7 compound. Ammonium tetraborate tetrahydrate (ATB) was used as the source of Boron. The compound was obtained using high-temperature solid-state reaction technique (840°C) and heat treatment process was introduced to enhance the phase purity and crystallinity. To control the formation of calcium tetraborate single phase, an excess amount of B2O3 (2wt%) was added to the starting powder mixture. Various analytical methods such as X-ray diffraction (XRD), Raman and Fourier transform infrared (FTIR) spectroscopies, Field emission scanning electron microscopy (FE-SEM), and X-ray photoelectron spectroscopy (XPS) were employed to characterize the prepared sample. Phase purity and crystallinity were evaluated by X-ray diffraction analytic method. Raman and FTIR spectroscopies were performed to confirm the atomic bond formation and its borate anionic group. FE-SEM was carried out for the morphological study of α-CaB4O7 compound and Energy dispersive X-ray (EDX) analysis was used to investigate the elemental composition of the prepared sample. XRD analysis confirmed that the prepared sample has alpha phase structure with monoclinic symmetry. The peaks correspond to unwanted phases (CaB2O4, Ca2B6O11) were not observed in the X-ray diffraction pattern of the prepared CaB4O7 compound. XPS was performed and its spectrum showed all expected characterization peaks for the first time, which is in agreement with FE-SEM and EDX results.
关键词： CaB4O7 compound,solid-state reaction,phase purity,highly crystalline
更新于2025-09-23 15:21:21
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Optimizing domain size and phase purity in all-polymer solar cells by solution order aggregation and confinement effect of the acceptor
摘要： Domain size, phase purity, and the interpenetrating network within the active layer of all-polymer solar cells (all-PSCs) are crucial for efficient charge generation and carrier transport. However, it is a great challenge to decrease domain size and enhance phase purity simultaneously because of the energetically disfavoring polymer-polymer mixing and chain entanglement. In this work, we manipulated the domain size and phase purity of J51:N2200 blends by promoting their solution ordered aggregation and the confinement of acceptor N2200 to J51 during phase separation. Thus, three solvents, chloroform (CF), mesitylene (Mes), and cyclopentyl methyl ether (CPME) were selected. The solubility of J51 and N2200 in these three solvents decreases solubility differences between J51 and N2200 increases gradually. Among these three solvents, only in CPME solution, N2200 possesses ordered structures, which reduces nucleation barrier to increase nucleation density and boosts template effect of N2200. During phase separation, the ordered aggregation of N2200 dominates solid-liquid phase separation and has the confinement effect of J51. Thus, the blend films cast from CPME have fine-scale phase separation in contrast to the films from CF. In addition, the "memory" effect of ordered aggregations transferred to films can enforce the order of blend films. As a result, the blend film with small domain size (≈21 nm), interpenetrating network structure, and a higher degree of crystallinity was obtained by processed from green solvent CPME. The improved morphology facilitated charge-generating process and carrier transport, resulting in higher short-circuit current (Jsc), fill factor (FF), and the power conversion efficiency (PCE).
关键词： all-polymer solar cells,domain size,phase purity,solution ordered aggregation,confinement effect
更新于2025-09-11 14:15:04