Among all inorganic halide perovskite photovoltaic materials, CsPbIBr2 exhibits the most balanced features in terms of bandgap and stability. However, the poor quality of solution‐processed CsPbIBr2 ...films impedes further optimization of cells performance. Herein, a facile intermolecular exchange strategy for CsPbIBr2 film is demonstrated, wherein an optimized methanol solution of CsI is spin‐coated on CsPbIBr2 precursor film in conventional one‐step solution route. It surprisingly produces full‐coverage and pure‐phase CsPbIBr2 films featured with average grain size of ≈0.65 µm, few grain boundaries, high crystallinity, preferable (100) orientation, stoichiometric composition along with favorable electronic structures for effective dissociation and transfer of carriers. Hence, the cost‐effective, carbon‐based all‐inorganic planar perovskite solar cells based on them, yield an optimized efficiency of 9.16% with a stabilized value of 8.46% in ambient air conditions that highlight a particularly superb open‐circuit voltage of 1.245 V, all of which represent the highest values reported in pure CsPbIBr2 based cells so far. Moreover, the optimized cell without encapsulation shows excellent long‐term stability because it can retain 90% over 60 days and 97% over 7 days of its initial efficiency, when is stored controllably in ≈45% relative humidity at 25 or 85 °C at zero humidity, respectively.
A carbon‐based all‐inorganic planar CsPbIBr2 solar cell with a record efficiency of 9.16%, an extremely high open‐circuit voltage of 1.245 V, and excellent long‐term stability is achieved by a facile intermolecular exchange strategy. Its impressive performance mainly derives from the desirable features of CsPbIBr2 film including full coverage, high crystallinity, preferable (100) orientation, and stoichiometric composition along with favorable electronic structure.
Perovskite/PCBM heterojunctions are efficient for fabricating perovskite solar cells with high performance and long-term stability. In this study, an efficient perovskite/PCBM heterojunction was ...formed via conventional sequential deposition and one-step formation processes. Compared with conventional deposition, the one-step process was more facile, and produced a perovskite thin film of substantially improved quality due to fullerene passivation. Moreover, the resulting perovskite/PCBM heterojunction exhibited more efficient carrier transfer and extraction, and reduced carrier recombination. The perovskite solar cell device based on one-step perovskite/PCBM heterojunction formation exhibited a higher maximum PCE of 17.8% compared with that from the conventional method (13.7%). The device also showed exceptional stability, retaining 83% of initial PCE after 60 days of storage under ambient conditions.
The inferior crystallinity and phase stability of CsPbI2Br films have severely hindered the development of carbon-based, all-inorganic perovskite solar cells (PSCs). Herein, we demonstrate the ...preparation of CsPbI2Br films by the top-seeded solution growth (TSSG) technique. It is performed through spin-coating of CH3NH3Br (MABr) atop CsPbI2Br precursor film prior to annealing, during which perovskite seeds are generated atop it. These perovskite seeds not only serve as nuclei to regulate the growth of CsPbI2Br grains but also provide additional Br– anions to generate a thin Br-rich layer atop the final CsPbI2Br film. The former contributes to the formation of CsPbI2Br film with full coverage, larger grains, higher crystallinity, and fewer electronic defects, while the latter gives rise to residual compressive strain along the film and thus markedly boosts its phase stability. Consequently, the optimized carbon-based, all-inorganic PSC exhibits a much better efficiency of 14.84% coupled with favored storage and operational stability.
With the fast development of the perovskite solar cell, its energy conversion efficiency has improved rapidly. In this paper, a CH3NH3PbI3–x Cl x organic–inorganic perovskite solar cell (PSC) was ...successfully prepared by the one-step solvent engineering method, and the planar heterojunction perovskite solar cell was optimized by interface engineering of the cathode interlayers. It was found that TiCl4 treatment could effectively reduce the TiO2 surface roughness, decrease the surface defects, improve the perovskite thin film crystallinity, and reduce the charge carrier recombination; hence, the short-circuit current density of PSCs and charge extraction and collection efficiencies were enhanced. Furthermore, PC60BM fullerene treatment could optimize the contact condition and reduce the interfacial potential loss. The device hysteresis effects after PCBM treatment were also reduced. The combination of TiCl4 and PC60BM treatments could largely improve the PSC device performance with a power conversion efficiency of 16.4% due to the synergetic effect.
The performance of perovskite solar cells (PSCs) is extremely dependent on the morphology and crystallization of the perovskite film. However, the complete conversion of PbI2 to perovskite and ...controlling the perovskite crystal size as well as its surface morphology are challenging in the conventional two-step sequential deposition method. We herein present a facile method involving the use of a polar solvent additive in an inter-diffusion two-step sequential deposition method to achieve a high-quality perovskite film. The results showed that the addition of a small amount of DMF solvent into the MAI precursor solution could help the complete conversion of PbI2 to perovskite, and at the same time could also reduce the pinholes, improve the film morphology, increase the grain sizes and enhance the film absorption ability. The improved perovskite film quality results in the boosting performance of PSCs. Consequently, an optimized device with power conversion efficiency as high as 19.2% is obtained. This current method provides a highly repeatable route for enhancing the PSC performance with the inter-diffusion sequential solution deposition method.
This report systematically investigates the influence of different carrier gases (O2, N2, and air) on the growth of gallium oxide (Ga2O3) thin films on c-plane sapphire substrates by using the ...mist-CVD method. Although XRD and Raman measurements show that the pure corundum-structured α-Ga2O3 with single (0006) plane orientation was successfully obtained for all three different carrier gases, the crystal quality could be greatly affected by the carrier gas. When O2 is used as the carrier gas, the smallest full-width at half maximum (FWHM), the very sharp absorption cutoff edge, the perfect lattice structure, the highest growth rate, and the smooth surface can be obtained for the epitaxial α-Ga2O3 film as demonstrated by XRD, UV-VIS, TEM, AFM (Atomic Force Microscope), and SEM measurements. It is proposed that the oxygen content in carrier gas should be responsible for all of these results. XPS (X-ray photoelectron spectroscopy) analysis also confirms that more oxygen elements can be included in epitaxial film when O2 is used as the carrier gas and thus help improve the crystal quality. The proper carrier gas is essential for the high quality α-Ga2O3 growth.
A high-performance transfer printing method using a new soluble tape which can be dissolved in acetone is proposed to be used in heterogeneous integration. Si inks array was transferred from SOI ...wafers onto various substrates without adhesion promoter by this new method which we refer to as the acetone soluble tape (AST) method to compare with other transfer printing methods by using thermal release tape (TRT), water soluble tape (WST) and polydimethylsiloxane (PDMS). By using the AST method, the transfer printing process does not involve interface contention between stamp/inks and inks/receiver substrate so that it maximizes the transfer printing efficiency. Experimental results present the AST method has good performances, and various alien substrates, even curvilinear surfaces, can be selected as receiver substrates by the AST method. To examine the quality of the transferred Si inks, the Si TFTs were fabricated by using the Si membrane transferred by the AST method on sapphire substrate and the devices show the good performance. All the results confirm that the AST method is an effective method in heterogeneous integration.
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•Hydroiodic acid additive triggers extreme sensitivity of grain sizes to CH3NH3PbI3 precursor stoichiometry.•Precursor stoichiometry engineering enables CH3NH3PbI3 film with average ...grain size of ∼1.75 μm.•Large-grained CH3NH3PbI3 film realizes the perovskite solar cell with efficiency of 19.29%.
We demonstrate that the sensitivity of grain sizes to precursor CH3NH3I/PbI2 molar ratio can be promoted by hydroiodic acid additive for one-step spin-coated CH3NH3PbI3 film. Thus, the full-coverage, high-crystallinity CH3NH3PbI3 film with average grain size of ∼1.75 μm can be obtained by simply adjusting precursor molar ratio. Planar perovskite solar cell (PSC) with this desired film yields the optimized efficiency of 19.29%. Hence, our work suggests a facile precursor stoichiometry engineering through the assistance of hydroiodic acid to obtain efficient CH3NH3PbI3 PSCs.
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•A high performance perovskite solar cell with the PEIE interlayer is demonstrated.•The obviously enhanced uniformity for the devices with PEIE interlayer are achieved.•The PEIE layer ...can suppress the trap-assisted recombination for the devices.•The stability of the corresponding device is also improved.
In this work, we demonstrated a high performance planar heterojunction perovskite solar cell with the polyethylenimine ethoxylated (PEIE) interlayer. By adopting a less polar solvent for PEIE, enhanced device performance and uniformity are achieved. The power conversion efficiency (PCE) of the best device increases by 22% compared to the reference device and reaches 14.82% with JSC of 19.45mA/cm2, VOC of 1.00V, and FF of 76.31% under AM 1.5G 100mW/cm2 light illumination. The UPS measurement shows that the PEIE layer can effectively decrease the energy offset between PCBM and metal electrode. The recombination mechanism was explored by measuring VOC and JSC at various light intensities from 100 to 0.1mW/cm2. It shows that the PEIE layer can suppress the trap-assisted recombination for the devices. The enhancement of the probability of the carriers collection also shows that the recombination is reduced by the PEIE interlayer. Moreover, it is found PEIE layer can improve the stability of the device.
In this work, flexible solar blind Ga 2 O 3 ultraviolet photodetectors with high responsivity and photo-to-dark current ratio are demonstrated. The Ga 2 O 3 films are obtained by the RF magnetron ...sputtering method on flexible polyimide (PI) substrates and the results demonstrate that all the films grown under various temperatures are amorphous. When the incident light wavelength is less than 254 nm, the incident light is effectively absorbed by the Ga 2 O 3 film. By controlling the growth temperature of the material, the responsivity and photo-to-dark current ratio of the corresponding metal-semiconductor-metal photodetectors are significantly improved. At growth temperature of 200 °C, the current under 254 nm illumination obtains 396 nA at voltage of 20 V (corresponding responsivity is 52.6 A/W), the photo-to-dark current ratio is more than 10 5 , and the external quantum efficiency reaches 2.6 × 10 4 %, which is among the best reported Ga2O3 ultraviolet photodetectors including the devices on the rigid substrates. After the bending and fatigue tests, the flexible detectors have negligible performance degradation, showing excellent mechanical and electrical stability.
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