The Structural and Dielectric Properties of Bi3−xNdxTi1.5W0.5O9 (x = 0.25, 0.5, 0.75, 1.0)

A new series of layered perovskite-like oxides Bi3−xNdxTi1.5W0.5O9 (x = 0.25, 0.5, 0.75, 1.0) was synthesized by the method of high-temperature solid-state reaction, in which partial substitution of bismuth (Bi) atoms in the dodecahedra of the perovskite layer (A-positions) by Nd atoms takes place. X-ray structural studies have shown that all compounds are single-phase and have the structure of Aurivillius phases (APs), with close parameters of orthorhombic unit cells corresponding to space group A21am. The dependences of the relative permittivity ε/ε0 and the tangent of loss tgσ at different frequencies on temperature were measured. The piezoelectric constant d33 was measured for Bi3−xNdxTi1.5W0.5O9 (x = 0.25, 0.5, 0.75) compounds of the synthesized series.

The Rational Control of Precursor Concentration in Perovskite Light-Emitting Diodes

Perovskite light-emitting diodes (PeLEDs) have attracted tremendous attention due to their ideal optoelectronic properties, such as high color purity, high fluorescence quantum yield, and tunable light color. The perovskite layer plays a decisive role in the performance of PeLEDs and the solvent engineering of the perovskite layer is the key technological breakthrough in preparing high quality films. In this study, we have proposed the strategy of adding different amounts of solvents to the perovskite precursor solution to optimize the morphology of perovskite films and device performance. As a result, with the decreasing concentration of perovskite precursor solution, the perovskite film morphology is smoother and more favorable for carrier injection and combing, which induces an enhanced external quantum efficiency. The maximum luminance of PeLEDs was increased from 1667 cd/m2 to 9857 cd/m2 and the maximum current efficiency was increased from 6.7 cd/A to 19 cd/A. This work provides a trend to achieve improved film morphology and device performance for perovskite optoelectronic devices.

Reveal the large open-circuit voltage deficit of all-inorganic CsPbIBr2 perovskite solar cells

Due to excellent thermal stability and optoelectronic properties, all-inorganic perovskite is one of the promising candidates to solve the thermal decomposition problem of conventional organic-inorganic hybrid perovskite solar cells (PSCs), but the larger voltage loss (V loss) cannot be ignored, especially CsPbIBr2, which limits the improvement of efficiency. To reduce the V loss, one promising solution is the modification of the energy level alignment between perovskite layer and adjacent charge transport layer (CTL), which can facilitate charge extraction and reduce carrier recombination rate at perovskite/CTL interface. Therefore, the key issues of minimum V loss and high efficiency of CsPbIBr2-based PSCs were studied in terms of the perovskite layer thickness, the effects of band offset of CTL/perovskite layer, the doping concentration of the CTL, and the electrode work function in this study based on device simulations. The open-circuit voltage (V oc) is increased from 1.37 V to 1.52 V by replacing SnO2 with ZnO as electron transport layer (ETL) due to more matching conduction band with CsPbIBr2 layer.

Surface-Passivated CsPbBr3 for Developing Efficient and Stable Perovskite Photovoltaics

All-inorganic perovskites consisting of only inorganic elements have been recently considered as highly stable semiconductors for photoactive layer of optoelectronics applications. However, the formation of high-quality thin film and trap-reduced interface has still remains an important task, which should be solved for improving the performances of all-inorganic perovskite-based photovoltaics. Here, we adopted facile method that could reduce charge-carrier recombination by depositing a passivation agent on the top surface of the CsPbBr3 all-inorganic perovskite layer. We also found that the CsPbBr3 perovskite photovoltaic prepared from surface treatment method using n-octylammonium bromide provides an improved stability in ambient environment and 1-sun illuminating condition. Therefore, the perovskite photovoltaics fabricated from our approach offered an improved power conversion efficiency of 5.44% over that of the control device without surface treatment (4.12%).

Improving the triple-cation perovskite solar cells by two-step deposition methods with perovskite seeds

As of recent years, triple-cation perovskite solar cells have received immense attention due to its superior efficiency and better stability comparing to the classic single-cation perovskite solar cells such as MAPbI3 or FAPbI3. A triple-cation perovskite layer which has been used most recently is cesium-containing FAPbI3-based perovskite. One of decent approaches to fabricate the layer is spin-coating technique by using two-step deposition process in which mixed lead-halide and CsI precursor is firstly spin-coated onto a substrate, then organic cation solution is deposited on the lead-halide layer. In this work, the results show that the performance of the devices from this process is lower than expected that could be due to difficulty of cesium ion incorporation as a stabilizer for FAPbI3-based perovskite. Perovskite seeding growth is introduced to solve the problem where the process is slightly modified from conventional two-step deposition methods by adding small amount of perovskite seed precursor into PbI2 solution. The concentration of the perovskite seed in PbI2 solution was varied for 0, 7, 14 and 20% v/v. The highest average efficiency of 11.9% was obtained from 7% v/v seeding concentration. Furthermore, the device performance could be improved by using proper amount of chlorobenzene (CB) as an anti-solvent. The highest efficiency of 18.4% was achieved by using 30 µl of chlorobenzene.

Enhanced Perovskite Solar Cell Performance by Adding Magnesium Acetate Using Two-Step Spin-Coating Method

The poor stability of perovskite materials is a problem of concern in commercialization. In this study, we investigated the doping of magnesium cations (Mg2+) in PbI2 to improve the stability and efficiency of perovskite solar cells. The doping effect of Mg2+ can increase the crystallization rate. The perovskite film fabricated structure consists of ITO/TiO2/perovskite/CuO. The fabrication method used is a two-stage spin coating. The concentrations of MgAc2 were used 0, 0.75, 1, and 1.25 mg ml−1. The characterizations used are XRD (X-Ray Diffraction), UV-Vis, SEM-EDX. While the performance of solar cells is measured using a solar simulator. The XRD pattern shows that the sample has a crystal structure of MAPbI3, PbI2, and CuO phases. The MAPbI3 lattice parameter increased with increasing Mg acetate concentration. The grain size of the perovskite layer is between 5 - 15 μm, with a thickness of about 30 μm. The efficiency of perovskite solar cells increases with the increasing concentration of MgAc2.

Effect of Deposit Au thin Layer Between Layers of Perovskite Solar Cell on Cell's Performance

The present work aims to fabricate n-i-p forward perovskite solar cell (PSC) withئ structure (FTO/ compact TiO2/ compact TiO2/ MAPbI3 Perovskite/ hole transport layer/ Au). P3HT, CuI and Spiro-OMeTAD were used as hole transport layers. A nano film of 25 nm gold layer was deposited once between the electron transport layer and the perovskite layer, then between the hole transport layer and the perovskite layer. The performance of the forward-perovskite solar cell was studied. Also, the role of each electron transport layer and the hole transport layer in the perovskite solar cell was presented. The structural, morphological and electrical properties were studied with X-ray diffractometer, field emission scanning electron microscope and current-voltage (J-V) characteristic curves, respectively. J-V curves revealed that the deposition of the Au layer between the electron transport layer (ETL) and Perovskite layer (PSK) reduced the power conversion efficiency (PCE) from 3% to 0.08% when one layer of C. TiO2 is deposited in the PSC and to 0.11% with two layers of C. TiO2. Power conversion efficiency, with CuI as the hole transport layer (HTL), showed an increase from 0.5% to 2.7% when Au layer was deposited between PSK and CuI layers. Also, Isc increased from 6.8 mA to 17.4 mA and Voc from 0.3 V to 0.5V. With depositing Au layer between P3HT and PSK layers, the results showed an increase in the efficiency from 1% to 2.6% and an increase in Isc from 10.7 mA to 30.5 mA, while Voc decreased from 0.75 V to 0.5V

Dual-function of the ZnO nano-sheets as light absorber scaffold and electron transport material in perovskite solar cells

Recent advances in the development of perovskite solar cells using CH3NH3PbI3 as the absorber material have reached over 18.7% in power conversion efficiency. The best performance perovskite-based cells required support of a mesoporous charge collector. In this work we present a new process for preparing perovskite solar cells with the structure of AZO/Au/AZO(AAA)/ZnO-sheets/CH3NH3PbI3/HTM/Au. Herein, ZnO nanosheets layer was prepared by electrochemical deposition method using zinc nitrate hexahydrate as nutrient solution, then annealed at 150 °C in ambient air. The results show that high crystal ZnO sheets assembled simply from AZO top layer could act as electron transporter and scaffold for perovskite layer. The presentation of ZnO scaffold was exploited to improve 19% in power conversion efficiency, offering great promise for further improvement of the low-temperature, low-cost processing solar technology.