Eco-Friendly Solvent Engineered CsPbI2.77 Br0.23 Ink for Large-Area and Scalable High Performance Perovskite Solar Cells.

The performance of large-area perovskite solar cells (PSCs) has been assessed for typical compositions, such as methylammonium lead iodide (MAPbI3 ), using a blade coater, slot-die coater, solution shearing, ink-jet printing, and thermal evaporation. However, the fabrication of large-area all-inorganic perovskite films is not well developed. This study develops, for the first time, an eco-friendly solvent engineered all-inorganic perovskite ink of dimethyl sulfoxide (DMSO) as a main solvent with the addition of acetonitrile (ACN), 2-methoxyethanol (2-ME), or a mixture of ACN and 2-ME to fabricate large-area CsPbI2.77 Br0.23 films with slot-die coater at low temperatures (40-50 °C). The perovskite phase, morphology, defect density, and optoelectrical properties of prepared with different solvent ratios are thoroughly examined and they are correlated with their respective colloidal size distribution and solar cell performance. The optimized slot-die-coated CsPbI2.77 Br0.23 perovskite film, which is prepared from the eco-friendly binary solvents dimethyl sulfoxide:acetonitrile (0.8:0.2 v/v), demonstrates an impressive power conversion efficiency (PCE) of 19.05%. Moreover, the device maintains ≈91% of its original PCE after 1 month at 20% relative humidity in the dark. It is believed that this study will accelerate the reliable manufacturing of perovskite devices.

Universal Surface Passivation of Organic-Inorganic Halide Perovskite Films by Tetraoctylammonium Chloride for High-Performance and Stable Perovskite Solar Cells.

The power conversion efficiency (PCE) of perovskite solar cells has been showing rapid improvement in the last decade. However, still, there is an unarguable performance deficit compared with the Schockley-Queisser (SQ) limit. One of the major causes for such performance discrepancy is surface and grain boundary defects. They are a source of nonradiative recombination in the devices that not only causes performance loss but also instability of the solar cells. In this study, we employed a direct postsurface passivation strategy at mild temperatures to modify perovskite layer defects using tetraoctylammonium chloride (TOAC). The passivated perovskite layers have demonstrated extraordinary improvement in photoluminescence and charge carrier lifetimes compared to their control counterparts in both Cs0.05(FAPbI3)0.83(MAPbBr3)0.17 and MAPbI3-type perovskite layers. The investigation on electron-only and hole-only devices after TOAC treatment revealed suppressed electron and hole trap density of states. The electrochemical study demonstrated that TOAC treatment improved the charge recombination resistance of the perovskite layers and reduced the charge accumulation on the surface of perovskite films. As a result, perovskite solar cells prepared by TOAC treatment showed a champion PCE of 21.24% for the Cs0.05(FAPbI3)0.83(MAPbBr3)0.17-based device compared to 19.58% without passivation. Likewise, the PCE of MAPbI3 improved from 18.09 to 19.27% with TOAC treatment. The long-term stability of TOAC-passivated perovskite Cs0.05(FAPbI3)0.83(MAPbBr3)0.17 devices has retained over 97% of its initial performance after 720 h in air.

Enhanced Perovskite Solar Cell Performance via 2-Amino-5-iodobenzoic Acid Passivation.

The intrinsic stability issues of the perovskite materials threaten the efficiency and stability of the devices, and stability has become the main obstacle to industrial applications. Herein, the efficient and facile passivation strategy by 2-amino-5-iodobenzoic acid (AIBA) is proposed. The impact of AIBA on the properties of the perovskite films and device performance is systemically studied. The results show that the trap states are eliminated without affecting the crystal properties of the perovskite grains, leading to the enhanced performance and stability of the perovskite solar cells (PSCs). A high power conversion efficiency (PCE) of 20.23% and lower hysteresis index (HI) of 1.49‰ are achieved, which represent one of the most excellent PCE and HI values for the inverted PSCs based on MAPbI3/[6,6]-Phenyl-C61-Butyric Acid Methyl Ester (PCBM) planar heterojunction structure. Moreover, the UV stability of the perovskite films and the thermal and moisture stability of the devices are also enhanced by the AIBA passivation. The PCE of the device with AIBA can maintain about 83.41% for 600 h (40 RH %) and 64.06% for 100 h (55-70 RH %) of its initial PCE value without any encapsulation, while the control device can maintain only about 72.91 and 45.59% of its initial PCE. Density functional theory calculations are performed to study the origins of enhanced performance. Interestingly, the results show that the surface states induced by AIBA can facilitate the photoexcited charge transfer dynamics and reduce the electron-hole recombination loss. The passivation method developed in this work provides an efficient way to enhance the stability and performance of inverted PSCs.

Structural, optical, photocatalytic, and optoelectronic properties of Zn2SnO4 nanocrystals prepared by hydrothermal method.

Zn2SnO4 (ZTO) nanocrystals are extensively studied in various fields. However, size-dependent ZTO nanocrystals are still challenging to understand their structural, optical, photocatalytic, and optoelectronic properties. ZTO nanocrystals are synthesized by a facile hydrothermal reaction method. The structural properties of the synthesized ZTO nanocrystals are studied by x-ray diffraction and transmission electron microscope. The sizes of the ZTO nanocrystals are controlled by the pH values of the precursor and the molar ratios of the Zn:Sn in the starting materials. ZTO nanocrystals with the small size of 6 nm and large size of 270 nm are obtained by our method. The Eu3+ ions are doped into ZTO nanocrystals to probe size-dependent Eu doping sites, which shows significant potential applications in light emitting diode phosphors. Moreover, the photocatalytic activity of ZTO nanocrystals on rhodamine (RhB) decoloration are investigated, and the results show that 6 nm ZTO nanocrystals show better performance in the photocatalytic decoloration of RhB compared to 270 nm nanocrystals. Most importantly, we design and fabricate optoelectronic devices to detect IR light based on our nanocrystals and a self-prepared NIR cyanine dye. The device based on small sized ZTO nanocrystals exhibits better device performance under 808 nm IR light compared to that of the large sized ZTO nanocrystals. We believe this work represents ZTO size-dependent properties in term of structural, optical, photocatalytic, and optoelectronic properties as a multifunctional material.

Concentrations, Sources, and TEQ of PCDD/Fs in Sediments from the Liaohe River Protected Areas.

A preliminary study was conducted to examine the contamination of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in surface sediments collected from the Liaohe River. The contamination levels of PCDD/Fs ranged from 317.3 to 509.3 pg/g dw. According to the calculated WHO-TEQ (Toxic Equivalent Quantity of World Health Organization), the range of PCDD/Fs is 13.87-40.88 pg/g dw. A principal component analysis and a cluster analysis suggested that PCDD/Fs in the sediments were mainly from gasoline/diesel vehicle emissions and solid waste incineration. The study revealed that the establishment of protected areas did not markedly reduced the ecological risk caused by PCDD/Fs in the Liaohe River protected areas sediments. It is necessary to study further the environmental impact of PCDD/Fs on the environment.

Toxicity assessment of sediments from the Liaohe River Protected Area (China) under the influence of ammonia nitrogen, heavy metals and organic contaminants.

The aim of this study was to evaluate the toxicity of ammonia nitrogen, metals and organic contaminants in sediment collected from the Liaohe River Protected Areas. The TIE was applied to 16 samples. The zeolite, resin, and coconut charcoal were used to mask toxicity of the three kinds of pollutants, respectively. Then quantitative analyses together with a battery of bioassays were performed to evaluate toxic effects. At last, the spiking tests were used to confirm the major contributors to toxicity. The results of toxicity identification showed the ammonia nitrogen, γ-HCHs, As and Cd may cause toxic hazards to benthic organisms. The significant correlation between the survival and volume ratio of the sediment and overlying water confirmed ammonia nitrogen and Cd were the major toxic pollutants that cause the biological toxicity. We confirmed bioassays combined with masking agent, spiking tests and quantitative analyses were suitable tools for detecting toxicity.