Passivating Agent Research Articles

Folic acid conjugated capecitabine capped green synthesized fluorescent carbon dots as a targeted nano-delivery system for colorectal cancer

Herein, we have developed folic acid conjugated capecitabine capped passivated carbon dots (CAP-FA-CDPs) for colorectal cancer targeting. Carbon dots were synthesized via a microwave treatment of the Buchnania lanzan leaf extract and PEG 6000 was used as a surface passivating agent. The developed system has shown an acidic pH (pH 5.0) dependent drug release of 84.57% after 72 h. In an in vitro cytotoxicity study, CDPs showed almost no toxicity to the HT-29 colorectal cancer cells with the viability rate of 96.03%. However, the viability of HT-29 cells significantly dropped to 24.4% in CAP-FA-CDPs treated group only after 36 h of incubation. A cellular uptake study showed an efficient internalization of CAP-FA-CDPs systems by HT-29 cells expected via folic acid-folate receptor (ligand-receptor) interactions. Greater reactive oxygen species (ROS) generation further confirmed the successful cellular uptake of the CAP-FA-CDPs. Finally, flow cytometry analysis clearly showed the apoptotic potential of the CAP-FA-CDPs conjugated system on HT-29 cells where live cells significantly decreased to 21.4% and apoptotic cells increased to 77.2%. Thus, the presently developed CAP-FA-CDPs nano delivery system offers a promising strategy for targeted and effective drug delivery in colorectal cancer. • Folic acid conjugated capecitabine capped CDs synthesized via microwave method. • Efficient internalization of CAP-FA-CDPs inside HT-29 cancer cells was seen. • In cytotoxicity study, CAP-FA-CDPs dropped HT-29 cancer cells count to 24.4%. • In FACS, apoptotic cells count was found 77.2% in CAP-FA-CDPs treated HT-29 cells.

Amplifying the Performance and Stability of Perovskite Solar Cells Using Fluorinated Salt as the Surface Passivator

The 3D‐halide perovskite‐based solar cells have shown outstanding power conversion efficiency, while the layered perovskite is emerging as the advanced version to deliver high stability. Galvanized with the surge of the report of layered perovskites, a common salt tetra‐n‐butyl ammonium hexafluorophosphate (TBAPF) as a passivating agent between perovskite and hole transporting layer that improves the power conversion efficiency and stability, is explored. The use of TBAPF as a surface passivator mitigates the surface defects and increases hydrophobicity. The fluorine atoms in TBAPF provide hydrogen bonding interaction with the hydrogen of organic ammonium cation in perovskite established by proton nuclear magnetic resonance techniques. Effective charge extraction to the hole transport layer is suggested by steady‐state photoluminescence measurements, showing higher quenching with the passivated perovskite compared to the pristine perovskite. The results suggest that TBAPF treatment improves the junction quality and minimizes the defects by virtue of H bonding, which in turn improves the photovoltaic parameters and long‐term stability.

Effects of Zn (II) on the Optical Properties of CdTe Quantum Dots and Their Photoluminescence Response to Lead Ion

Water-soluble CdTe quantum dots (QDs) have been utilized as photoluminescence probes for the detection of metal ions such as Pb2+, Hg2+, Cd2+, etc. We initially developed highly photoluminescence (PL) Zn-doped CdTe for toxic ions detection. A study on the changes of optical properties of Zn-doped CdTe and CdTe QDs when exposed to Pb2+ suggested that Pb2+ could act as a surface passivating agent to reduce Te2- dangling bonds while Zn2+ dopant stabilizes the QDs surface against ambient oxidation. The results demonstrated herein provide useful understandings of the interactions between water-soluble QDs and metal ions. These results suggest further applications of QDs in sensing metal ions.

Atomic layer deposition of diethylzinc/zinc oxide on InAs surface quantum dots: Self-clean-up and passivation processes

Passivation capping of molecular beam epitaxy (MBE)-grown InAs surface quantum dots (SQDs) is achieved by ex situ atomic layer deposition (ALD)-grown ZnO using diethylzinc (DEZ) as the zinc precursor, the main passivation agent, and oxygen plasma. Photoluminescence (PL) intensity is enhanced by 2-fold as the DEZ/ZnO passivation cap thickness reached 30 nm. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) show that contrary to conventional wet chemistry passivation or MBE capping, in which InAs SQDs can be damaged or be shrunken by intermixing of In and Ga, DEZ/ZnO passivation capping almost preserves the shape of the underlying SQDs. The cross-sectional analysis with transmission electron microscopy (TEM) reveals the formation of the ZnO grains on top of the sample accompanied by slight SQD height and width reduction, which are presumably related to the removal of the InAs native oxides. The DEZ “self-clean-up” passivation mechanism, where zinc precursor is responsible for reduction of the surface non-radiative recombination sites, is studied by X-ray photoelectron spectroscopy (XPS). The factors that control the DEZ “self-clean-up” efficiency such as the chain of chemical reactions, steric hindrance, decomposition activation energy, Gibbs reactivity, or Lewis acidity, are evaluated. The results are discussed in comparison with trimethylaluminum (TMA), a precursor used for Al2O3 deposition. We find that the “self-cleaning” by DEZ and TMA occurs through processes of different chemical nature.

Enhancing the efficiency and stability of p-i-n triple cation perovskite solar cells using benzyl cyanoacetate passivation agent

It is extremely difficult to realize high-performance perovskite solar cells (PeSCs) due to a large number of defects of perovskite. Thus, perovskite defects should be passivated as much as possible. In this study, effective cyano (CN), benzene ring, and carbonyl (CO) functional groups were newly introduced to benzyl cyanoacetate (BCA) to prepare a multifunctional BCA passivation agent. The influence of functional group of BCA passivation molecule on perovskite and PeSCs was systemically studied using cyanoethyl acrylate (CA) with CN without benzene ring and benzyl acrylate (BA) with benzene ring without CN as reference molecules. Through various analyses, we found that the novel BCA passivation agent with both CN and benzene ring passivated perovskite defects the most efficiently. Thus, the combination of each effective functional group can synergistically passivate more perovskite defects. As a result, PeSCs created using BCA showed improved power conversion efficiency (PCE) from 18.38 % to 20.23 %. Additionally, PeSC with BCA retained 70 % of the initial PCE after ∼2034 h of air exposure test, 80 % of the initial PCE after ∼193 h of heat aging test, and 60 % of the initial PCE after ∼72 h of light-soaking test, demonstrating better stability than PeSC without BCA in air/heat/light-soaking stability.

Photocationic Initiator Induced Synergy for High‐Performance Perovskite Solar Cells

The perovskite structures are prone to decomposition due to the formation of defect sites under various stressors. As a result, the stability of perovskite materials has been an Achilles’ heel in actual commercialization. Herein, photocationic initiator based on 4‐isopropyl‐4'‐methyldiphenyliodonium tetrakis(pentafluorophenyl)borate (TPFB) is introduced into perovskite film through the antisolvent process to enhance the efficiency and stability of perovskite solar cells. The hypervalent iodine part serves as a Lewis acid to passivate the negatively charged defects, while the pentafluorophenyl borate part is used to tailor the crystallization process by forming strong hydrogen bonding. Furthermore, the superior hydrophobicity of TPFB insulates the perovskite films. The resulted MAPbI3 devices show maximum power conversion efficiency (PCE) reaching 20.41% and ultrahigh open voltage (Voc) up to 1.15 V with the remaining 85% efficiency after 1000 h shelf storage. Furthermore, by introducing TPFB through a simple posttreatment process, the device delivers a PCE of 23.4% (steady‐state PCE of 23.2%), features useful for advanced double cation‐based perovskite device. In sum, these findings develop a universal passivation strategy and open a novel field of Lewis acid‐based passivation agent.

Multifunctional Ionic Fullerene Additive for Synergistic Boundary and Defect Healing of Tin Perovskite to Achieve High-Efficiency Solar Cells.

A series of new ionic fullerene derivatives (C60-RNH3-X; X = Cl, Br, or I) were designed especially for using as additives for tin perosvkite (TPsk, with chemical formula of FA0.98EDA0.01SnI3) to form TPsk-C60-RNH3-X bulk heterojunction (BHJ) films. Inverted tin-perovskite solar cells (TPSCs) based on BHJ TPsk-C60-RNH3-Br absorber achieved the highest power conversion efficiency up to 11.74% with very high FF of 73%, without current hysteresis and stable in a glovebox. The designed spherical ionic fullerene halide additive, sitting in the grain boundaries of the TPsk film, can not only improve the quality of the TPsk film and change the valence band energy to match better with the PEDOT:PSS hole transporter but also be a carrier transporting connector between tin-perovskite grains, the defects/traps passivation/healing agent by interacting with Sn2+ ions and filling the halogen vacancies. The functions of the ionic fullerene halide additive were revealed with XRD patterns, SEM images, element mapping, UPS spectra, infrared spectra, AFM, and SCLC data. Being able to passivate newly generated defects during device operation or sitting on the shelf is an important step to improve the long-term stability of TPSCs. If a passivation agent can move dynamically during cell operation or storage to heal the defects of perovskite, the instability problem of TPSCs can be alleviated. The spherical ionic fullerene halide could be one of the ideal passivation agents satisfying this purpose.

Regulating coordination by multi-configurational alkaloid-based passivation molecules for high-performance perovskite photovoltaics

Abundant defects in polycrystalline perovskite will destroy the photovoltaic performance and accelerate the degradation of perovskite solar cells (PSCs). The development of effective management for multiple defects is obviously important to promote the practical application of perovskite photovoltaics. Herein, we firstly introduced the strategy of employing natural alkaloid passivation agents (adenine and cytosine) to achieve the directed management of lead- and iodide-based defects. Owing to the various configurations of alkaloid molecules, the electron cloud density distributions for different functional groups display adjustable characteristic, which closely related to the passivation effect. As a result, the CO with high electron density can form stronger Pb-O coordination with uncoordinated Pb2+ rather than the Pb-N bond (imidazole ring with Pb2+), leading to fewer lead-based defects being generated. The stronger electron-withdrawing ability of the CO further promotes the hydrogen bond of –NH2 and I-/Br- to reduce I-/Br- vacancies. Finally, the devices with cytosine perform the champion PCE of 22.07 % and dramatically enhance open-circuit voltage (Voc = 1.19 V), as well as much better environmental stability. This work provides a new insight on rationally design the non-toxic, cheap and accessible passivation molecules structure for achieving the efficient and stable PSCs.

Analysis and Treatment of Abnormal Defects in Transformer Oil Chromatography

This article analyzes the cause of an abnormal defect in the oil chromatogram of a transformer, and puts forward control measures and suggestions. It is analyzed that the cause of the abnormal oil chromatogram of phase A and B of the main transformer is the poor contact o f the dynamic and static contacts of the unloaded tap changer, high temperature and overheatin g, and the development of contact ablation, resulting in abnormal oil chromatogram. The cause of the ablation of the dynamic and static contacts of the no-load tap-changer may be due to the installation and transportation (or electrodynamic shock or U-switch design and other factors), the contacts are not in close contact, the larger contact resistan ce causes the contacts to overheat, and high temperature conditions Sulfur corrosion occurs on the surface of the lower contact, and the corrosion product gradually deposits on the surface of the contact, which further aggravates the poor contact. Although passivation agent is added in t he later period, the protection effect of the passivation agent at high temperature is limited, and it can no longer protect the contact. Under the action of current, the dynamic and static contacts that cause poor contact are gradually ablated.

Improvement of Open‐Circuit Voltage Deficit via Pre‐Treated NH4+ Ion Modification of Interface between SnO2 and Perovskite Solar Cells

Passivation is a popular method to increase power conversion efficiency (PCE), reduce hysteresis related to surface traps and defects, and adjust mismatched energy levels. In this paper, an approach is reported using ammonium chloride (AC) to enhance passivation effects by controlling chlorine (Cl) and ammonium ions (NH4 + ) on the front and back side of tin oxides (SnO2 ). AC pre-treatment is applied to indium tin-oxide (ITO) prior to SnO2 deposition to advance the passivation approaches and compare the completely separated NH4 + and Cl passivation effects, and sole NH4 + is successfully isolated on the SnO2 surface, the counterpart of AC-post-treatment, generating ammonia (NH3 ) and Cl. It is demonstrated that multifunctional healing effects of NH4 + are ascribed from AC-pre-treatment being the basis of SnO2 crystallization and adjusting bifacial interface energy levels at ITO/SnO2 and SnO2 /perovskite to enhance photo-carrier transport. As calculated by density functional theory, how the change of the passivation agent from Cl to NH4 + more effectively suppresses non-radiative recombination ascribed to hydrated SnO2 surface defects is explained. Consequently, enhancement of photo-carrier transport significantly improves a superior open-circuit voltage of 1.180 V and suppresses the hysteresis, which leads to the PCE of 22.25% in an AC-pre-treated device 3.000% higher than AC-post-treated devices.

High quantum yield carbon quantum dots as selective fluorescent turn-off probes for dual detection of Fe2+/Fe3+ ions

Carbon quantum dots (CQDs) are fluorescent nanoparticles that have great potential for use as nontoxic fluorescent probes. However, synthesizing CQDs with high photoluminescence quantum yield (QY) in a rapid and facile way from commonly available and low-cost reagents is still challenging. In this work, Tween®80 was used as a surface passivation agent along with citric acid/urea in a one-step microwave procedure to make extremely blue luminous nitrogen doped CQDs. When excited at 350 nm, these CQDs had a fluorescent quantum yield of 75.5 %. The significant high quantum yield and stability of these CQDs are attributed to the high aromatic sp2 domain size within the CQD core and improved carbon and oxygen functional groups at the CQDs surface. We employed the CQDs as a fluorescent probe to detect Fe2+ and Fe3+ ions and could establish a linear relationship between photoluminescence quenching efficiency (F0-F/F0) and ion concentration with a detection limit of 6.5 µM and 2.5 µM for Fe2+ and Fe3+, respectively. Our studies suggest that the highly selective detection of iron ions is a result of partial transfers of excited electrons from the CQDs to the d orbital of the iron ions, instead of contributing to radiative relaxation that induces photoluminescence quenching of the CQDs. Other reported carbon dots for this application have a substantially lower quantum yield and only detect Fe3+ ions. Therefore, our CQDs have considerable benefits over similar probes. Subsequent research may adapt them to other areas due to the high quantum yield and stability.

Fabrication of sulfur quantum dots via a bottom-up strategy and its application for enhanced fluorescence monitoring of o-phenylenediamine

Nowadays, the synthesis of luminescent sulfur quantum dots (SQDs) mainly depends on a top-down method, which requires abnormally long reaction time by etching bulk sulfur powder. To overcome this limitation, a facile bottom-up strategy has been provided to fabricate fluorescent SQDs enabled by the reaction between thioacetamide (TAA) and hydrogen peroxide (H2O2) using carboxymethyl cellulose (CMC) as a passivation agent. Herein, TAA acts as sulfur source to release sulfide ions (S2-), which react directly with H2O2 to generate element sulfur to assemble the CMC-stabilized SQDs (SQDs@CMC). The prepared SQDs@CMC emits blue fluorescence, and owns good water dispersibility, superior photostability, excitation dependent luminescence and a reasonable quantum yield up to 9.31 %. Herein, the prepared SQDs@CMC combined with Cu2+ has a sensitive response toward o-phenylenediamine (OPD) by forming ternary SQDs@CMC/Cu2+/OPD complex, which can emit enhanced blue-shift fluorescence. The fluorescence of the ternary complex is 10 times higher than that of SQDs@CMC and the proposed SQDs@CMC-Cu2+ assembly has been successfully used to monitor OPD in various waters with high selectivity. Therefore, this paper not only provides a bottom-up strategy to prepare SQDs, but also develops a novel fluorescence “turn on” sensing platform for OPD detection.

Broad-Spectrum Antibacterial Activity of Synthesized Carbon Nanodots from d-Glucose.

Carbon nanodots, a class of carbon nano-allotropes, have been synthesized through different routes and methods from a wide range of precursors. The selected precursor, synthetic method, and conditions can strongly alter the physicochemical properties of the resulting material and their intended applications. Herein, carbon nanodots (CNDs) have been synthesized from d-glucose by combining pyrolysis and chemical oxidation methods. The effect of the pyrolysis temperature, equivalents of oxidizing agent, and refluxing time were studied on the product and quantum yield. In the optimum conditions (pyrolysis temperature of 300 °C, 4.41 equiv of H2O2, 90 min of reflux) CNDs were obtained with 40% and 3.6% of product and quantum yields, respectively. The obtained CNDs are negatively charged (ζ-potential = -32 mV), excellently dispersed in water, with average diameter of 2.2 nm. Furthermore, ammonium hydroxide (NH4OH) was introduced as dehydrating and/or passivation agent during CNDs synthesis resulting in significant improvement of both product and quantum yields of about 1.5 and 3.76-fold, respectively. The synthesized CNDs showed a broad spectrum of antibacterial activities toward different Gram-positive and Gram-negative bacteria strains. Both synthesized CNDs caused highly colony forming unit reduction (CFU), ranging from 98% to 99.99% for most of the tested bacterial strains. However, CNDs synthesized in the absence of NH4OH, due to a negatively charged surface enriched in oxygenated groups, performed better in zone inhibition and minimum inhibitory concentration. The elevated antibacterial activity of high-oxygen-containing carbon nanodots is directly correlated to their ROS formation ability.

Restructuring and Reshaping of CsPbX3 Perovskites by Lithium Salts

AbstractMetal halide perovskites have exceptional potential for future generations of light‐emitting diodes and solar cells. Compared to widely used solution‐based syntheses, vapor‐phase deposition (VPD) offers a fabrication route that can be more easily scaled up for commercial production. Cesium lead halides (CsPbX3) have shown great color purity, high photoluminescence quantum yield, and better stability than other perovskites. To improve the optoelectronic properties, lithium salts are often used as passivation agents to reduce nonradiative defects. Here, it is reported that VPD CsPbX3 thin films can be dramatically reshaped by a lithium bromide adlayer, a salt that is successfully used to drastically increase the luminescent yield of CsPbBr3. It is found that continuous CsPbBr3 and CsPbCl3 films restructure themselves into islands whereas CsPbI3 films transform into mixed triangular and rod‐shaped crystals. Based on density functional theory (DFT) studies, it is established that a surface energy change by LiBr adlayer is not the main driver for the perovskite film transformation. Instead, DFT simulations indicate that the LiBr adlayer creates a polar surface forming a strong Van der Waals force attracting water molecules.

Reduced Confinement Effect by Isocyanate Passivation for Efficient Sky‐Blue Perovskite Light‐Emitting Diodes

AbstractCompared with green and red perovskite light‐emitting diodes (PeLEDs), the development of blue PeLEDs has been lagging due to high defect density and inferior carrier transport. Herein, a novel defect‐passivation strategy is proposed to fabricate efficient sky‐blue PeLEDs by using isocyanate molecules. This strategy not only significantly reduces the nonradiative recombination loss caused by defects but also improves the injection and transport capacities of carriers by reducing the confinement effect. Benefiting from the passivation engineering and the reduction of confinement effect, the prepared sky‐blue PeLEDs present a significantly improved external quantum efficiency of 12.5% at 489 nm, which is 1.5 times higher than that of the control device. Meanwhile, the universality of isocyanate‐based passivators to improve the performance of PeLEDs is also demonstrated. The finding of this study provides a new reference for the selection of novel passivation agents to construct highly efficient blue PeLEDs.

Improved efficiency and stability of organic-inorganic hybrid perovskite solar cell via dithizone surface passivation effect

Passivating chemicals are recognized as an effective strategy to eliminate the defects inside and on the surface of the perovskite absorber. In this study, dithizone (DTZ) was explored as the passivation agent to modify the perovskite surface and improve the performance of the solar cells. DTZ contains the –NH, –SH, and benzene rings, where the –NH and –SH can interact with Pb 2+ while the benzene can stabilize the perovskite. It is demonstrated that DTZ could effectively promote the quality of the perovskite films by reducing the excess lead iodide and defects on the surface, and eventually suppressing the non-radiative carrier recombination. Furthermore, the introduction of the DTZ interface can optimize the band alignment to facilitate the hole collection. Resultantly, device parameters, including current density, open-circuit voltage, fill factor, and the power conversion efficiency have been enhanced substantially from 16.96% to 19.67%. Meanwhile, the shelf stability also exhibited a considerable promotion. • Dithizone is explored as an effective passivating chemicals for the perovskite surface. • The excess lead iodide and non-radiative carrier recombination are reduced after dithizone treatment. • The efficiency is enhanced from 16.96% up to 19.67%.

Energy spacing and sub-band modulation of Cu doped ZnSe quantum dots

Cu doped ZnSe quantum dots (QDs) with various dopant concentrations were prepared using a growth doping technique to modulate their kinetics of Cu incorporation. Pre-synthesized ZnSe QDs with a low defect concentration and strong band-edge emission were fabricated under controlled reaction conditions, resulting from the low surface-to-volume ratio. The growth doping process was used to synthesize Cu doped ZnSe QDs and growth doping completed interior doping used Cu as a doping agent. The Cu doping overcomes the wavelength constraints of ZnSe QDs and enables elimination of the ZnSe host emission due to the formation of Cu states. Increasing the Cu dopant concentration to 0.4% resulted in an increase in the Cu-related emission intensity owing to the dominant recombination pathway which transfers to the Cu states, demonstrating the successful incorporation of Cu dopant atoms. The emission wavelength tuning of ZnSe QDs through Cu doping is clearly independent of the size variation, as evidenced by the ZnSe and Cu doped ZnSe QDs exhibiting similar nanoscale features. • Cu doped ZnSe quantum dots were fabricated using growth doping strategy. • Correlation between optical band gap and quantum dot size was investigated based on empirical approximation. • Formation of sub-bands states resulting from Cu incorporation achieves wavelength extension of ZnSe quantum dots. • Controlled doping level was limited due to passivating agents and formation of CuSe nanoparticles.

Passivation strategies of Perovskite film defects for solar cells by bifunctional amides with various molecular structures

Defects passivation is one of the efficient strategies for improving the performances of perovskite solar cells (PSCs) as well as to regulate crystal growth of perovskite by passivators. However, the synergist effect of various functional groups in the molecular structure of passivators on defects passication has not been systematically reported. Herein, we use three amide molecules, including iodoacetamide (IAM), benzamide (BA), and cyanoacetamide (CAM), to analyze the influences of different functional groups on the passivation and performances of PSCs. These molecules have the same amine group and different terminal groups, which are iodine, phenyl, and cyan respectively. The results demonstrated that phenyl is more effective to coordinate with amide in defect passivation than the iodine and cyano groups, which is more beneficial to the growth of perovskite grain, defects reduction, and accelerated charge transfer compared with the other terminal groups own to the π-π conjugation and hydrophobicity. After BA passivation, the power conversion efficiency (PCE) of PSCs increases by 31%. Remarkably, the un-encapsulated BA-modified device displayed lower hysteresis factor after 30 days of ageing process under 60% relative humidity (RH), with an initial PCE retention rate of 92%. The above results indicated that the molecules with bifunctional groups can reduce the dosage of passivation agents and enhance the passivation effects. This work provided guidance for the selection of new passivation molecular configurations in perovskite photovoltaic materials in the future. • Three amide molecules with different end groups are applied to study the effect of defect passivation in perovskite film. • Compared with the iodine and cyano groups, phenyl is more effective to coordinate with amide in defect passivation. • Passivated by additive with phenyl and amide groups, the PCE of the device increases by 31% compared to the control device.

Performance enhancement of cost-effective mixed cationic perovskite solar cell with MgCl2 and n-BAI as surface passivating agents

The perovskite layer and its composition play a vital role in the fabrication of perovskite solar cells (PSCs) in order to achieve high power conversion efficiency (PCE) with great stability. The use of mixed cations in the perovskite layer could lead to PCE up to 25.8% in 2021. However, due to the effect of environmental factors such as heat and moisture, the perovskite layer shows undesirable degradation and lead leakage. This hindrance can be solved by the use of surface passivation and additive engineering strategies along with the knowledge of thermal stress testing. In the present study, optoelectronic properties and stability of mixed cationic perovskite solar cell have been successfully enhanced by two additives, namely, MgCl2 and n-BAI. The impact of its concentration on optoelectronic properties and stability of mixed cationic PSC is also investigated in detail. The results show that, 2 mol% n-BAI (used as an additive) on perovskite layer enhances the photovoltaic properties of perovskite and it gives superior stability against environmental stressors. The PCE of cell increases by 39.86% (from 5.92% to 8.28%) post additive engineering. PSC sample treated with 2 mol% n-BAI shows substantial increase in hydrophobicity. Treated cell gives superior PCE retention as compared to untreated sample. Also, the treated sample shows promising stability results compared to untreated cell, after stress testing by international standards (along with superior resistance against recombined electrons). Thus, the present work will open the means for successful commercialization of mixed cation PSCs.

Dually-passivated planar SnO2 based perovskite solar cells with ˃2,700h ambient stability: Facile fabrication, high performance and mechanism

In SnO2-based planar perovskite solar cells (SP–PSCs), stability issue derived by defects at grain boundaries (GBs) and surface in perovskite films has been one of the main reasons that limit its commercialization. Therefore, co-passivation of both defects is pivotal to maximize passivation effects for improving power conversion efficiency (PCE) and stability, which is rarely reported in SP-PSCs. Herein, two simple passivating agents including Pb(SCN)2 and choline chloride (ChCl) were selected to dually passivate GBs and surface defects in the perovskite films (ambient atmosphere), respectively. The influences of co-passivation on PCE and ambient stability of devices were intensively studied, and the related mechanisms were also elucidated in detail. The dually-passivated device obtained a champion PCE of 19.98%, and maintained about 94% of the initial efficiency after being stored for ˃2700h aging in the humid air. The reduction of GBs and surface defects not only weakens the non-radiative recombination of carriers, but also inhibits the penetration of moisture and oxygen, which ultimately greatly enhances the PCE and stability of the device. This paper provides support for the dual passivation of GBs and surface defects to ameliorate ambient stability of the SP-PSCs, and also enriches the selectivity of passivation agents on dual passivation.