All-inorganic CsPbI2Br perovskite has attracted increasing attention, owing to its outstanding thermal stability and suitable bandgap for optoelectronic devices. However, the substandard power conversion efficiency (PCE) and large energy loss (E-loss) of CsPbI2Br perovskite solar cells (PSCs) caused by the low quality and high trap density of perovskite films still limit the application of devices. Herein, the post-treatment of evaporating cesium bromide (CsBr) is utilized on top of the perovskite surface to passivate the CsPbI2Br-hole-transporting layer interface and reduce E-loss. The results of microzone photoluminescence indicate that the evaporated CsBr gathered at the grain boundaries of CsPbI2Br layers and Br-enriched perovskites (CsPbIxBr3-x, x < 2) are formed, which can provide protection for CsPbI2Br. Therefore, the gaps between crystal grains are filled up, and the recombination loss of the all-inorganic CsPbI2Br PSCs is reduced accordingly. The champion device exhibits high open-circuit voltage and a PCE of 1.271 V and 16.37%, respectively. This is the highest reported PCE among all-inorganic CsPbI2Br PSCs reported so far. In addition, the stability of CsPbI2Br PSCs is effectively improved by CsBr passivation, and the device without encapsulation can retain 86% of its initial PCE after 1368 h of storage, which is beneficial for practical applications.
All-inorganic CsPbI2Br perovskite has attracted increasing attention, owing to its outstanding thermal stability and suitable bandgap for optoelectronic devices. However, the substandard power conversion efficiency (PCE) and large energy loss (E-loss) of CsPbI2Br perovskite solar cells (PSCs) caused by the low quality and high trap density of perovskite films still limit the application of devices. Herein, the post-treatment of evaporating cesium bromide (CsBr) is utilized on top of the perovskite surface to passivate the CsPbI2Br-hole-transporting layer interface and reduce E-loss. The results of microzone photoluminescence indicate that the evaporated CsBr gathered at the grain boundaries of CsPbI2Br layers and Br-enriched perovskites (CsPbIxBr3-x, x < 2) are formed, which can provide protection for CsPbI2Br. Therefore, the gaps between crystal grains are filled up, and the recombination loss of the all-inorganic CsPbI2Br PSCs is reduced accordingly. The champion device exhibits high open-circuit voltage and a PCE of 1.271 V and 16.37%, respectively. This is the highest reported PCE among all-inorganic CsPbI2Br PSCs reported so far. In addition, the stability of CsPbI2Br PSCs is effectively improved by CsBr passivation, and the device without encapsulation can retain 86% of its initial PCE after 1368 h of storage, which is beneficial for practical applications.
Flexible perovskite solar cells (PSCs) were ideal candidates for wearable devices due to the merits of flexibility, high efficiency, and being lightweight, and they could be fabricated in a continuous roll-to-roll production process to achieve large-area and low cost devices. Herein, the high efficiency (up to 18.53%) and fill factor (0.81) of flexible PSCs (ITO/SnO2/KCl/MAPbI(3)/spiro-OMeTAD/Ag) were achieved by low-pressure assisted solution processing under low temperature (<= 100 degrees C). The surface morphology and crystallinity of perovskite films were effectively promoted by the KCl modification and the defect density of perovskite films as well as the hysteresis of the corresponding devices was reduced accordingly. In addition, the stability and bendability of the KCl-modified flexible PSCs were improved simultaneously. To the best of our knowledge, both the efficiency and fill factor are the best among all flexible PSCs reported to date. Therefore, the insertion of KCl between SnO2 and MAPbI(3) layers provided a promising strategy for highly efficient flexible PSCs fabricated in low temperature (<= 100 degrees C) conditions.
Flexible perovskite solar cells (PSCs) were ideal candidates for wearable devices due to the merits of flexibility, high efficiency, and being lightweight, and they could be fabricated in a continuous roll-to-roll production process to achieve large-area and low cost devices. Herein, the high efficiency (up to 18.53%) and fill factor (0.81) of flexible PSCs (ITO/SnO2/KCl/MAPbI(3)/spiro-OMeTAD/Ag) were achieved by low-pressure assisted solution processing under low temperature (<= 100 degrees C). The surface morphology and crystallinity of perovskite films were effectively promoted by the KCl modification and the defect density of perovskite films as well as the hysteresis of the corresponding devices was reduced accordingly. In addition, the stability and bendability of the KCl-modified flexible PSCs were improved simultaneously. To the best of our knowledge, both the efficiency and fill factor are the best among all flexible PSCs reported to date. Therefore, the insertion of KCl between SnO2 and MAPbI(3) layers provided a promising strategy for highly efficient flexible PSCs fabricated in low temperature (<= 100 degrees C) conditions.
Flexible perovskite solar cells (PSCs) were ideal candidates for wearable devices due to the merits of flexibility, high efficiency, and being lightweight, and they could be fabricated in a continuous roll-to-roll production process to achieve large-area and low cost devices. Herein, the high efficiency (up to 18.53%) and fill factor (0.81) of flexible PSCs (ITO/SnO2/KCl/MAPbI(3)/spiro-OMeTAD/Ag) were achieved by low-pressure assisted solution processing under low temperature (<= 100 degrees C). The surface morphology and crystallinity of perovskite films were effectively promoted by the KCl modification and the defect density of perovskite films as well as the hysteresis of the corresponding devices was reduced accordingly. In addition, the stability and bendability of the KCl-modified flexible PSCs were improved simultaneously. To the best of our knowledge, both the efficiency and fill factor are the best among all flexible PSCs reported to date. Therefore, the insertion of KCl between SnO2 and MAPbI(3) layers provided a promising strategy for highly efficient flexible PSCs fabricated in low temperature (<= 100 degrees C) conditions.
We propose a high order numerical method for computing time dependent 4-D Wigner equation with unbounded potential and study a canonical quantum double-slit interference problem. To address the difficulties of 4-D phase space computations and higher derivatives from the Moyal expansion of nonlocal pseudo-differential operator for unbounded potentials, an operator splitting technique is adopted to decompose the 4-D Wigner equation into two sub-equations, which can be computed analytically or numerically with high efficiency. The first sub-equation contains only linear convection term in $(\bm x, t)$-space and can be solved with an advective method, while the second involves the pseudo-differential term and can be approximated by a plane wave expansion in $\bm k$-space. By exploiting properties of Fourier transformation, the expansion coefficients for the second sub-equation have explicit forms and the resulting scheme is shown to be unconditionally stable for any higher derivatives of the Moyal expansion, ensuring the feasibility of the 4-D Wigner numerical simulations for quantum double-slit interferences. Numerical experiments demonstrate the spectral convergence in $(\bm x, \bm k)$-space and provide highly accurate information on the number, position, and intensity of the interference fringes for different types of slits, quantum particle masses, and initial states (pure and mixed).
Perovskite solar cells (PSCs) have been paid more attention because of its high power conversion efficiency (PCE) and flexible applications. Low temperature process for PSCs is critical for high performance flexible devices and industrial applications. Herein, the photovoltaic properties of the PSCs based on a polyelectrolyte interfacial layer of polyethyleneimine (PEI) were studied in this work and the configuration of PSCs was indium fin oxide (ITO)/PEI/SnO2/perovskite/spiro-OMeTAD/Ag. Due to the spin-coated PEI on ITO substrates, smooth cathodes (ITO/PEI) with low work function were obtained and the champion PCE of 19.36% and 16.81% for the rigid and flexible devices respectively was achieved accordingly. Moreover, the PCE of the rigid and flexible PSCs with PEI (0.1 mg mL(-1)) remained similar to 95% and similar to 90% of the initial values respectively after 80 days in ambient conditions. Meanwhile, the PCE of the flexible PSCs based on PEI (0.1 mg mL(-1)) remained 85% of the initial value after 100 bending cycles and the bendability of the flexible PSCs was improved accordingly. All the experimental data implied that the fabrication of PEI onto ITO electrodes was an effective way to promote the photovoltaic properties of the low-temperature processed rigid and flexible PSCs.
The global energy crisis and water pollution drive the researchers to develop highly effective and less energy intensive water purification technologies. In this study, a highly active WO3@TiO2–SiO2 nanocomposite was synthesized and used for photocatalytic degradation of persistent organic pollutants under simulated solar light. The optimum WO3@TiO2–SiO2 prepared with 2 wt% WO3 loading and calcination at 800 °C exhibited higher photocatalytic activity, as the rate constant (k1) for phenanthrene degradation was ∼7.1 times of that for the commercial TiO2 (P25). The extremely large specific surface area (>400 m2/g) of WO3@TiO2–SiO2 afforded it with enlarged pollutants adsorption performance and abundant active surface sites. The heterojunction of anatase with SiO2 as well as loading of WO3 decreased the band gap energy (Eg) of TiO2, which extended the utilization spectrum of TiO2 to visible region. Formation of Ti–O–Si band indicated the excess charges can cause Brønsted acidity due to the absorption of protons to compensate the charges. Moreover, the migration of photo-excited electrons from the conduction band of anatase to WO3 and holes in the opposite direction restrained the electron-hole recombination. The photocatalytic degradation mechanism and pathway for phenanthrene degradation were proposed based on experimental analysis and density functional theory (DFT) calculation, and the toxicities of the degradation intermediates were evaluated by quantitative structure–activity relationship (QSAR) analysis. WO3@TiO2–SiO2 also showed good separation (settling) performance and high stability. Our work is expected to offer new insight into the photocatalytic mechanism for WO3, TiO2 and SiO2 based heterojunctions, and rational design and synthesis of highly efficient photocatalysts for environmental application.