Good Light Stability Research Articles

Theoretical Understanding of Structure-Property Relationships in Luminescence of Carbon Dots.

Carbon dots (CDs) have excellent luminescence characteristics, such as good light stability, high quantum yield (QY), long phosphorescence lifetime, and a wide emission wavelength range, resulting in CDs' great success in optical applications. Understanding the structure-property relationships in CDs is essential for their use in optoelectronic applications. However, because of the complex nature of CD structures and synthesis processes, understanding the luminescence mechanism and structure-property relationships of CDs is a big challenge. This Perspective reviews the theoretical efforts toward the understanding of structure-property relationships and discusses the challenges that need to be overcome in future development of CDs.

A novel lysosome‐localized fluorescent probe with aggregation‐induced emission without alkalinizing effect

AbstractHerein, a novel small molecule probe, tetraphenylethylene‐cystein (TPE‐Cys), was rationally designed and developed for the intracellular lysosome localization. The combination of tetraphenylethylene and cysteine serve as a novel strategy for lysosome‐targeting, with significant aggregation‐induced emission increases with the proportion of water by as high as 25‐folds. Biofluorescence imaging experiments show that the probe TPE‐Cys has a good colocalization effect with the commercially available lysotracker red, with a Pearson correlation coefficient of 0.91. In addition, we also demonstrate that TPE‐Cys has good light stability. TPE‐Cys, as a neutral compound, is free of alkalinizing effect when applied in lysosome localization. Moreover, molecular dynamics simulations and density function theories are employed to explore the detailed aggregation process and the mechanism of TPE‐Cys aggregation in water solution. The mechanism of lysosome localization of probe TPE‐Cys was explained by cellular endocytosis process and the formation of larger particle in the more acidic environment of lysosomes. This work not only demonstrates an efficient strategy for the construction of fluorescent probes for lysosome localization, but also indicates that they are promising as live cell imaging tools.

A two-photon “turn-on” fluorescent probe for both exogenous and endogenous selenocysteine detection and imaging in living cells and zebrafish

Selenocysteine (Sec) is recognized as the 21st amino acid employing as an essential building block for selenoproteins (SePs), which plays a significant role in various physiological processes. Therefore, there is an urgent need to reasonably develop some reliable and rapid methods for Sec detection in biological systems. In this work, we reported a new two-photon (TP) fluorescent probe BNT-Sec for Sec detection and imaging in living cells and zebrafish with two part: (1) a D-π-A-structured naphthalene derivative as a TP fluorophore; (2) a well-know Sec responsive site with strong intromolecular charge transfer effect (ICT) to selectively detect endogenous and exogenous. In the presence of Sec, probe BNT-Sec can initiate a Se-dependent specific aromatic nucleophilic substitution reaction, which exhibited BNT-Sec had a large fluorescence intensity enhancement with ~18.9-fold at 510 nm, a high sensitivity low LOD value’ 10.6 nM, good light stability, strong specificity, pH stability and low cytotoxicity. In addition, BNT-Sec can be conveniently used to detect Sec in living cells and zebrafish for TP imaging due to the great TP measurement properties of fluorophore, exhibiting it has the potential to reveal the role of selenocysteine in physiological and pathological processes in further biological applications.

Silver particle on BiVO4 nanosheet plasmonic photocatalyst with enhanced photocatalytic oxidation activity of sulfadiazine

Herein, we successfully prepared decahedral BiVO4 at low temperature and formed BiVO4 nanosheet (S-BiVO4) by changing the morphology of surfactant addition, then fabricated a series of Ag/S-BiVO4 plasmonic photocatalysts by photo-deposition method. The photocatalytic activity of the sulfadiazine solution was investigated by irradiation in visible light, among which Ag/4S-BiVO4 (The mass ratio between AgNO3 and S-BiVO4 nanosheet is 1:4) had the highest photocatalytic performance. The degradation rate of Ag/4S-BiVO4 photocatalyst can reach the highest 91.31% within 4 h of visible light irradiation, which is about 1.78 and 2.95 times as high as that of S-BiVO4 (51.39%) and BiVO4 (30.96%), respectively. The excellent degradation activity may be summarized as the SPR effect induced by silver nanoparticles, which enhances the absorption in the visible light region and effectively promotes the separation of photogenerated electron-hole pairs. This result has also been verified by UV–Vis diffuse reflection and fluorescence spectroscopy. In addition, XRD and Raman spectroscopy show that the synthesized samples have monoclinic structure. FDTD simulation results confirm the surface plasmon resonance and electric field enhancement caused by silver nanoparticles. The active species of ·O2− and h+ are pivotal in photocatalytic oxidation of sulfadiazine solution. Furthermore, the material has good light stability and recyclability.

Supramolecular self-assembly and application of metal clusters

Metal nanoclusters (NCs) are relatively stable aggregates composed of several to several thousand metal atoms through physical or chemical bonding, and their size is generally less than 3 nm. It has excellent quantum size effect and has outstanding applications in many fields such as optics, electricity, magnetism, catalysis, chirality, etc. However, NCs have poor optical properties at room temperature, which limits their further applications in the optical field. Therefore, the assembly of metal clusters with different types of molecular materials is driven by non-covalent bonds inspired by the concepts of “aggregation-induced emission” (AIE) and “supramolecular chemistry”, which can not only regulate the optical properties of metal clusters, but also can realize multi-functional coordination. As an important category of supramolecular chemistry, self-assembly provides a way to construct ordered structures from the bottom up. Self-assembly mainly uses non-covalent interactions to precisely control the specific structure of the building element to obtain functionalized micro-nano materials. Supramolecular self-assembly is one of the hot research fields in the chemical industry. It has been widely used in biomedicine, environment, sensing, optoelectronic devices and catalysis due to its simple operation and easy availability of raw materials. Herein, firstly, this paper introduces the effect of self-assembly on the assembly structure in detail combining the research work of this research group and related research on the self-assembly of design metal clusters at home and abroad. The research involving the aggregation morphology and morphology of metal nanoclusters is currently in its infancy in the world, and is a relatively popular research topic. Therefore, the self-assembly strategy to achieve the control of the aggregation morphology and morphology of metal nanoclusters can enrich the research field of self-assembly and realize the functionalization of metal nanoclusters. Secondly, fluorescence is one of the most important properties of metal clusters. Compared with traditional PL materials, the quantum yield (QY) of metal nanoclusters is relatively low. In addition, the proportion of fluorescent metal nanoclusters is also very low. Therefore, precise control of the metal composition and clearly defined surface chemistry factors not only provide a basis for a firm understanding of the structure and fluorescence, but also provide a method for the design and preparation of new nanoclusters with PL enhancement and adjustable emission wavelength. Hence, the vibration and rotation of the ligands around the metal core can be effectively restricted, and non-radiative transitions can be reduced, thereby achieving enhanced fluorescence through self-assembly. The fluorescence intensity and emission wavelength of the metal clusters can be controlled by controlling the assembly conditions of the metal clusters. The effect of self-assembly on the luminescence of metal clusters is commonly regulated by solvent regulation, pH, and co-assembly of other molecules to obtain highly stable luminescent clusters. In addition, the research progress in the application of metal cluster assembly and other aspects are summarized. Although precious metal nanoclusters have been used in chemical sensing, biological fields, catalysis and light conversion materials, the stability of the metal nanoclusters itself is relatively poor and the fluorescence is relatively weak. The assembly of nanoclusters can well solve the above shortcomings. The cluster aggregates have strong PL intensity, good light stability, and wide emission wavelength, which makes it a new type of fluorophore used in chemical sensing, biological fields, catalysis and light conversion materials. Finally, the improved scope and future prospects of the new nanoclusters are summarized and emphasized. Our review is expected to open up new horizons for these scientists to effectively control the functional properties of nanoclusters.

Near-infrared absorption photothermal conversion polyurethane film for energy storage

A series of near infrared absorption photothermal conversion polyurethane (PTPU) was synthesized with a cyanine dye to act as near infrared absorption component and polyethylene glycol 10,000 (PEG10000) to act as phase change material (PCM). The light resistant, pH dependence of dye and the effect of PEG10000 content on the properties of PTPU were investigated. The results showed that the cyanine dye had good light stability and was sensitive to pH, so a saturated solution of boric acid was added in the synthesis of PTPU to adjust its pH to 6 ~ 7. The crystalline degree of PTPU increased and its thermal stability decreased with the increasing of PEG10000 content; the light absorption of PTPU was mainly determined by the dye; the photothermal conversion efficiency and energy storage capability of PTPU increased with the increasing of PEG10000 and the PTPU can reach a higher temperature under illumination comparing to control polyurethane (PU); the PTPUs underwent a solid–solid phase change process and had excellent durability.

A novel aggregation-induced dual emission probe for in situ light-up detection of endogenous alkaline phosphatase

Abnormal level of alkaline phosphatase (ALP) activity has been linked to many diseases in human. The development of fluorescent molecular probes that can report the expression and activity of ALP in various biological systems will be extremely valuable. However, the in vivo monitoring for ALP in living cells and more complex biological systems remains a great challenge. The excited-state intramolecular proton transfer (ESIPT) probe with proportional fluorescence has low background noise, while the aggregation induced emission (AIE) probe has the advantages of signal amplification and good light stability. Herein, an “AIE + ESIPT” fluorescent probe 2-(benzo[d]thiazol-2-yl)-4-(1,4,5-triphenyl-1H-imidazole-2-yl)phenyl dihydrogen phosphate (THP) was constructed for the highly selective and sensitive detection of ALP. By introducing a phosphate ester at the hydroxyl position of the solid fluorophore 2-(benzo[d]thiazol-2-yl)-4-(1,4,5-triphenyl-1H-imidazole-2-yl)phenol, ESIPT was hindered and the probe present a faint blue fluorescence in DMSO solution. While ALP was introduced, causing the phosphate in THP hydrolyzed, and the ESIPT process was restored to yield a yellow fluorescence at 550 nm, thereby achieving proportionality detection. THP exhibited high selectivity and sensitively to ALP with low limit of detection (1.21228 U/L), and the reaction completed within 20 min. In addition, with its outstanding advantages of low biological toxicity and enzyme conversion characteristics, THP has been successfully applied to ALP imaging in living cells (Hela cells, A549 cells and Hek293 cells), and can provide in situ information on the reaction site. Therefore, THP has the potential for detecting ALP activity in biomedical application.

Construction of Chlorine Labeled ZnO–Chitosan Loaded Cellulose Nanofibrils Film with Quick Antibacterial Performance and Prominent UV Stability

Inside Cover: In article number 2000228, Xuehong Ren, Xinyu Zhang, and co-workers reportsa facile, universal, and cost-effective technique of preparing CNF/ZnO-CS-Cl films, combining vacuum filtration and heat-press processing without the use of any organic solvent. The produced biocompatible CNF/ZnO-CS-Cl hybrids have a quick antibacterial activity, good UV light stability, and favorable physical property, which are applicable for food packaging materials.

Selective Oxidation of Benzyl Alcohol by Ag/Pd/m-BiVO4 Microspheres under Visible Light Irradiation

A series of Ag/Pd/m-BiVO4 (monoclinic) bimetallic photocatalytic materials with different loading amounts and different mass ratios of Ag and Pd were synthesized by a hydrothermal method and an NaBH4 reduction method. The Ag/Pd/m-BiVO4 photocatalyst with a total Ag and Pd loading of 2 wt% and an Ag-to-Pd mass ratio of 2:1 can selectively oxidize benzyl alcohol to benzaldehyde under visible light irradiation, the conversion rate was up to 89.9%, and the selectivity was greater than 99%. The conversion rate on Ag/Pd/m-BiVO4 was higher than those on Ag/m-BiVO4 and Pd/m-BiVO4. The photocatalysts were characterized by X-ray powder diffraction (XRD), ultraviolet-visible diffuse reflection spectroscopy (UV-vis DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy, N2 adsorption-desorption isothermal curves (BET) and other means. The effects of different light wavelengths and light intensities were compared. Then, the effects of different alcohol derivatives on the reactions were explored. The cycle experiments proved that the Ag/Pd/m-BiVO4 photocatalyst had good light stability and thermal stability. In addition, the capturing experiment of active species shows that the selective oxidation of benzyl alcohol is mainly accomplished through the synergistic action of h+, e−, •OH and •O2−.

Planar MgxZn1-xO-based perovskite solar cell with superior ultraviolet light stability

Generally, TiO2-based perovskite solar cell (PSC) is beneficial to high efficiency but poor ultraviolet (UV) light stability. Here, we report that a highly efficient MgxZn1-xO-based (MZO-based) PSC with excellent UV light stability. MZO has a higher electron mobility and deeper conduction band than traditional TiO2, which can reduce the charge accumulation at the MZO/perovskite interface and enhance the charge transfer from perovskite to MZO. Furthermore, the reduced interface loss and energy barrier are beneficial to obtain high open-circuit voltage (Voc). By optimizing, the MZO-based device shows a high Voc of 1.11 V, yielding a promising efficiency of 19.57%. The MZO-based device (unencapsulated) retains 76% of its initial short-circuit current density (Jsc) after 1 year air aging (room temperature, relative humidity: 40–80%) and 8 h UV irradiation (365 nm, 35 W), versus only 12% under the same condition for TiO2-based device. The good UV light stability of MZO-based device can be attributed to the reduced electron trap-state density in MZO electron-transporting layer (ETL). Specifically, zinc interstitial and oxygen vacancy mediated defect sites of MZO ETL are effectively passivated, which tightly protects the perovskite layer from degradation under UV light. Our results show a great potential for MZO ETL application in UV-stable PSC.

Highly luminescent carbon dots as temperature sensors and “off-on” sensing of Hg2+ and biothiols

Here, Carbon dots (CDs) were fabricated through a simple one-step hydrothermal treatment of N-aminoethylpiperazine (AEP) and citric acid (CA). The as-prepared CDs have a bright blue emission with a quantum yield of 56%, with good water solubility, light stability and temperature sensitivity. In addition, the photoluminescence of the CDs deriving from two components was experimentally verified: one is amide molecules resulting from the reaction between AEP and CA, and the other is the carbon nucleus coming from the precursors at high temperatures. More importantly, the fluorescence intensity of the CDs is temperature-dependent, and decreasing linearly from 25 °C to 95 °C, with excellent sensitivity and recoverability. A CD/epoxy composite was prepared by doping the CDs into an epoxy resin, which exhibits superior temperature response that may be caused by the greater dielectric constant of epoxy resin. In addition, the fluorescence of the CDs can be efficiently quenched by Hg2+, and the addition of biothiols restore the quenched fluorescence of CDs. The sensor was applied to detect ions in river water and tap water and satisfied results were achieved.

Hydrogen Bond Induced Green Solvent Processed High Performance Ternary Organic Solar Cells with Good Tolerance on Film Thickness and Blend Ratios

AbstractFor comprehensive development of organic solar cells (OSCs), some factors such as environmental stability, low cost, insensitive film thickness, component contents tolerance, and green preparation processes are equally crucial to achieve high power conversion efficiencies (PCEs). In this work, a small molecule 3‐(diethylamino)‐7‐imino‐7H‐benzo[4,5]imidazo[1,2‐a]chromeno[3,2‐c]pyridine‐6‐carbonitrile (DIBC), which is commercially available at low cost, is utilized to realize high‐performance ternary OSCs. Demonstrated via Fourier transform infrared and 2D‐1HNMR, DIBC can form hydrogen bond interactions with [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM) in solid films. Further electrostatic potential (ESP) calculations indicate that the hydrogen bond interaction enhances the ESP of PC71BM and accelerates charge transport between donor and acceptor. As a result, poly(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐b;4,5‐b0]dithiophene‐2,6‐diylalt‐(4‐(2‐ethylhexyl)‐3‐fluorothieno[3,4‐b]thiophene‐)‐2‐carboxylate‐2‐6‐diyl (PTB7‐Th):DIBC:PC71BM‐based ternary OSC achieves a maximum efficiency of 12.17%, which is the best result of green solvent processed fullerene OSCs at present. It is noteworthy that the ternary OSCs also show great tolerance to film thickness and blend ratios. These unique properties are attributed to the hydrogen‐bond‐linked DIBC and PC71BM, which modulates molecule distribution and improves film morphology with an interpenetrating network structure. Furthermore, the DIBC containing device also exhibits good thermal and light radiation stability. These results illustrate that intermolecular hydrogen bond interaction has great potential for realizing high‐performance OSCs.

Investigation of rare earth upconversion fluorescent nanoparticles in biomedical field

Abstract Rare earth upconversion nanoparticles (UCNPs) with the superior performance in the biomedical field have attracted great attention. Due to the good light stability, low toxicity, deep tissue penetration and excellent bio-compatibility, UCNPs display great potential for development in the biomedical field. Excellent related reports are increasing year by year, like molecular sensing, bioimaging and therapeutics. In this paper, the preparation, modification, application of upconversion fluorescent nanoparticles and the latest research results in the field of biomedical materials have been reported in detail. Graphical abstract: In this paper, we systematically summarize and describe the preparation, modification, application and latest discovery in biomedical field of rare earth upconversion nanoparticles (UCNP). Due to the good light stability, low toxicity, deep tissue penetration and excellent biocompatibility, UCNPs display superior performance for the development of biomedical field in cancer therapy. Our work will certainly inspire researchers in related fields to create more meaningful upconversion nanomaterials and do more contributions to human cancer treatment research.

Curative effect evaluation of neoadjuvant chemotherapy by indocyanine green fluorescence imaging in pancreatic cancer

Objective To explore the imaging effectiveness of indocyanine green (ICG) in pancreatic cancer cells and curative effect evaluation of neoadjuvant chemotherapy in pancreatic cancer. Methods The basic characteristics of ICG was characterized and cell counting kit-8 (CCK-8) assay was used to observe the toxic effects of ICG and gemcitabine (GEM) in pancreatic cancer cell lines (ASPC-1 and PANC-1). After incubated with ICG for 4 hours, the ICG uptake in this two cells was observed by a high sensitivity optical imaging system (IVIS) respectively. A subcutaneous xenograft model of pancreatic cancer was established and then divided into phosphate buffer (PBS) + ICG injection group (control group) and GEM + ICG injection group (treatment group). After injection of PBS (100 mg/kg) or GEM (100 mg/kg) 24 hours, ICG (7 μg/ml) 200 μl was injected into mice by tail vein, then the fluorescence intensity in tumor tissue was observed continually by IVIS. Results ICG almost non-toxic to cells can be excited by near-infrared light also has a good dispersion and light stability. The fluorescence intensity in both control and GEM group of ASPC-1 cells was (2.437±0.039)×107 and (0.564±0.327)×107 respectively (F=13.262, P<0.05). Similarly, The fluorescence intensity in both control and GEM group of PANC-1 cells was (2.831±0.029)×107 and (0.376±0.019)×107 respectively (F=5.381, P<0.05). Fluorescence intensity of tumor was continuously measured by IVIS at different time points. After 4, 5 and 6 hours, the tumor fluorescence intensity in GEM group was stronger than that in control group respectively (P<0.05). Conclusion ICG can be absorbed by pancreatic cancer cells and accumulate in pancreatic tumor tissues after treated with GEM. Therefore, ICG fluorescence imaging can be used to evaluate efficacy of neoadjuvant chemotherapy in Pancreatic Cancer. Key words: Pancreatic cancer; Indocyanine green; Gemcitabine; Neoadjuvant chemotherapy; Fluorescence imaging

Origin and Suppression of the Graded Phase Distribution in Ruddlesden‐Popper Perovskite Films for Photovoltaic Application

Ruddlesden‐Popper perovskites (2D perovskites) show tremendous potential in photovoltaic devices for their superior stability compared with their 3D counterparts, while their lower power conversion efficiencies severely hinder their further progress for practical application. Generally, the 2D perovskite films fabricated by spin‐coating present graded distribution of 2D phases, and the small‐n phases located at the film bottom will impede the interlayer charge transport. In this work, the origin of the graded phase distribution is explained, and the roles of DMSO in Ruddlesden‐Popper perovskites film crystallization are systematically investigated. DMSO was found to homogenize the film composition, and therefore suppress the proportion of the small‐n 2D phases. Through X‐ray diffraction and grazing‐incidence wide‐angle X‐ray scattering measurements, it has been revealed that an intermediate phase is responsible for the less graded films and rationalizes the effect of DMSO in film crystallization. More importantly, solar cells with an efficiency exceeding 14% are fabricated by this facile method, which deliver good light, thermal, and ambient stability without encapsulation. These findings significantly benefit the understanding of crystal growth in 2D perovskites film and demonstrate that 2D perovskites are promising candidates for high‐performance solar cells.

Effect of visible light irradiation on hydrogen production by CoNi2S4/CdWO4 controllable flower spherical photocatalyst

The CoNi2S4/CdWO4-3 (CNS/CW-3) was an excellent photocatalyst for hydrogen evolution. The controlled morphology of CNS/CW-3 was successfully by adding thiourea as sulfur source and TBA to control the CoNi2S4 nanoparticles. The photocatalytic hydrogen evolution activity of CoNi2S4 and CdWO4 under visible light irradiation was studied with different CoNi2S4 incorporation ratios. UV–vis absorption spectra showed that the absorbance of CNS/CW-3 composite catalyst increased significantly after doping CoNi2S4. The electrochemical and photoelectrochemical experiments also showed that the charge separation and electron transfer efficiency were higher when CoNi2S4 was attached to CdWO4. CNS/CW-3 exhibited excellent photocatalytic activity for hydrogen evolution under visible light irradiation. Its hydrogen evolution activity reached 269.08 μmol in 5 h, and had good light stability. It was a potential strategy to design photocatalyst with controllable morphology.

Durable N-halamine Antibacterial Cellulose Based on Thiol-ene Click Chemistry

Antibacterial cotton fabrics were prepared with 3-allyl-5,5-dimethylhydantoin (ADMH) by UV photoinitiated thiol-ene click chemistry after 3-mercaptopropyltriethoxysilane (MPTES) was introduced on the surface of cotton fabrics. The treated cotton fabrics were characterized by SEM, FT-IR and EDS. After chlorination with diluted sodium hypochlorite, the treated samples showed good antibacterial efficacy against S. aureus and E. coli O157:H7. About 106 of S. aureus and E. coli O157:H7 could be completely inactivated within 1 min and 5 min of contact, respectively. Compared to the control samples, the antibacterial treatment method used in this study only had a minor effect on the tensile strength of cotton fabrics. Besides, the treated cotton fabrics showed good storage stability and 77 % of the active chlorine remained after 30 days. After exposure to bleach solution, almost all of the active chlorine was restored. The prepared antimicrobial cotton fabrics showed good washing and UV light stability.

RETRACTED: A Perovskite Solar Cell with Enhanced Light Stability and High Photovoltaic Conversion Efficiencies

Owing to the remarkable advantages of the perovskite solar cell (PSC), people regard the PSC as an auspicious candidate for photovoltaic devices in the near future, but light instability of the PSC, caused by TiO2 being a photo catalyst to decompose perovskite films under UV radiation, limits its practical applications. To improve light stability, removing the TiO2 layer from PSC devices is the best solution, but the photovoltaic conversion efficiencies (PCEs) of the reported TiO2-layer-free PSCs are much lower than TiO2-layer-containing PSCs. As such, via applying a chemical engineering technique of inserting a layer of bathophenanthroline (Bphen) between the ITO substrate and the perovskite film, we developed a TiO2-layer-free PSC with both good light stability and an averaged PCE of around 18.53%, much higher than that of those reported ones. The insertion of the Bphen layer caused a dramatic promotion of shunt resistances (Rsh), causing the improvements of the open circuit voltages (Voc), fill factors...

Effect of Mesoporous TiO2 Thicknesses on the Performance of Solid-State Dye-Sensitized Solar Cells

We report the fabrication of solid-state dye-sensitized solar cells (ss-DSSCs), using a metal-free organic dye (D102) as a sensitizer. Mesoporous TiO2 acting as a photoanode, is prepared from TiO2 nanopaste followed by drafting light-absorbing dye molecules. Spiro-OMeTAD is used as a hole transport material (HTM), which has a potential role in the energy conversion process of solid-state dye-sensitized solar cells (ss-DSSCs). Here, TiO2 mesoporous films are used with three different thicknesses (∼ 1.5 μm, ∼ 1.7 μm and ∼ 2.0 μm) for the device fabrication. Various characterizations of optimum TiO2 porous film (with the thickness of ∼ 2.0 μm) are performed such as ultraviolet–visible (UV–Vis) transmission, x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and cross-section scanning electron microscopy (SEM). Transmittance analysis reveals that transparency of the TiO2 films ranges from 70% to 80%. The x-ray diffraction (XRD) pattern of TiO2 shows anatase as its major crystalline phase. The porous structure formation of the TiO2 film is confirmed by scanning electron microscopy (SEM) cross section analysis. Photovoltaic performance of the devices was examined in air. Higher power-conversion efficiency (PCE) of 3.5% is obtained with optimum device thickness (∼ 2.3 μm). The device stability test is performed under continuous illumination for 2 h, showing slightly good air and light stability.

Dual Functions of Crystallization Control and Defect Passivation Enabled by Sulfonic Zwitterions for Stable and Efficient Perovskite Solar Cells.

Uniform and high-electronic-quality perovskite thin films are essential for high-performance perovskite devices. Here, it is shown that the 3-(decyldimethylammonio)-propane-sulfonate inner salt (DPSI), which is a sulfonic zwitterion, plays dual roles in tuning the crystallization behavior and passivating the defects of perovskites. The synergistic effect of crystallization control and defect passivation remarkably suppresses pinhole formation, reduces the charge trap density, and lengthens the carrier recombination lifetime, and thereafter boosts the small-area (0.08 cm2 ) planar perovskite device efficiency to 21.1% and enables a high efficiency of 18.3% for blade-coating large-area (1 cm2 ) devices. The device also shows good light stability, which remains at 88% of the initial efficiency under continuous unfiltered AM 1.5G light illumination for 480 h. These findings provide an avenue for simultaneous crystallization control and defect passivation to further improve the performance of perovskite devices.