Display omitted
•ZnO NCs as an interface layer improve the crystallinity and grain size of perovskite.•Increase in PCE of PSCs due to better charge extraction and lower recombination.•Interpretation ...of the ideality factor, EIS and IMVS for this PCE enhancement.
Hybrid perovskite solar cells (PSCs) have gained significant attention owing to their excellent physicochemical and photovoltaic properties. PSCs typically consist of a perovskite light absorber sandwiched between two carrier selective layers optimized with respect to optimal band alignment and low interfacial recombination. The quality of the perovskite layer and interfaces play major roles in the fabrication of high-performance PSCs. In the present work, we systematically investigate the planar structure PSCs based on TiO2 and TiO2/ZnO electron transport layers (ETLs), which provide deeper insight into the charge recombination and accumulation mechanisms. We show that the double-layer structure of TiO2/ZnO ETL improves the optical and morphology properties of perovskite film leading to superior device performance. From the ideality factor, EIS and IMVS results, a suppressed recombination in TiO2/ZnO PSCs is achieved, which is due to improved grain size of perovskite absorber layer grown on ZnO nanocrystals (NCs). Additionally, we find that the ZnO NCs improve the shunt resistance and quality of the perovskite and suppress the recombination. The present study provides a novel strategy to improve the device performance of PSCs along with a detail investigation procedure to understand the physical mechanism.
Zinc oxide (ZnO) is a promising electron‐transport layer (ETL) in thin‐film photovoltaics. However, the poor chemical compatibility between commonly used sol–gel‐derived ZnO nanostructures and ...organo–metal halide perovskites makes it highly challenging to obtain efficient and stable perovskite solar cells (PSCs). Here, a novel approach is reported for low‐temperature processed pure ZnO ETLs for planar heterojunction PSCs based on ZnO quantum dots (QDs) stabilized by dimethyl sulfoxide (DMSO) as easily removable solvent molecules. With no need for the ETL doping or surface modification, the champion PSC comprising the mixed‐cation and mixed‐halide Cs5(MA0.17FA0.83)95Pb(I0.83Br0.17)3 absorber layer reaches a maximum power conversion efficiency of 20.05%, which is significantly higher than that obtained for a reference device based on a standard sol–gel‐derived ZnO nanostructured layer (17.78%). Thus, along with the observed better operational stability in ambient conditions and elevated temperature, the champion device achieves the state‐of‐the‐art performance among reported non‐passivated pure ZnO ETL‐based PSCs. The improved photovoltaic performance is attributed to both a higher uniformity of the surface morphology and a lower defects density of films based on the organometallic‐derived QDs that are likely to ensure the enhanced stability of the ZnO/perovskite interface.
High quality colloidal ZnO quantum dots (ZnO OM) are synthesized using a new wet‐organometallic approach. The use of ZnO OM as an electron transfer layer (ETL) in planar perovskite solar cells improves the ETL/perovskite interface stability and reduces charge carrier recombination pathways. Consequently, the performance and stability of the ZnO OM‐based device is improved compared to the control device fabricated on the sol–gel processed ZnO ETL.
Among diverse chemical synthetic approaches to zinc oxide nanocrystals (ZnO NCs), ubiquitous inorganic sol–gel methodology proved crucial for advancements in ZnO‐based nanoscience. Strikingly, unlike ...the exquisite level of control over morphology and size dispersity achieved in ZnO NC syntheses, the purity of the crystalline phase, as well as the understanding of the surface structure and the character of the inorganic–organic interface, have been limited to vague descriptors until very recently. Herein, ZnO NCs applying the standard sol–gel synthetic protocol are synthesized with zinc acetate and lithium hydroxide and tracked the integration of lithium (Li) cations into the interior and exterior of nanoparticles by combining various techniques, including advanced solid‐state NMR methods. In contrast to common views, it is demonstrated that Li+ ions remain kinetically trapped in the inorganic core, enter into a shallow subsurface layer, and generate “swelling” of the surface and interface regions. Thus, this work enabled both the determination of the NCs’ structural imperfections and an in‐depth understanding of the unappreciated role of the Li+ ions in impacting the doping and the passivation of sol–gel‐derived ZnO nanomaterials.
The distribution of Li+ ions is comprehensively looked at in the interior and exterior of zinc oxide nanoparticles derived from a standard sol–gel synthetic protocol.
Despite various applications of alkylzinc carboxylates in chemistry and materials science, the corresponding organozinc derivatives of organophosphorus compounds still represent an insufficiently ...explored area. To fill this gap, we report on the synthesis of alkylzinc phosphinates and their use as efficient precursors of phosphinate‐coated ZnO nanocrystals in the quantum size regime. Examples of a series of alkylzinc phosphinates with the general formula RZn(O2PR′2) (R=tBu or Et) have been prepared through equimolar reactions between ZnR2 and a selected phosphinic acid, namely dimethylphosphinic acid (dmpha‐H), methylphenylphosphinic acid (mppha‐H), diphenylphosphinic acid (dppha‐H), or bis(4‐methoxyphenyl)phosphinic acid (dmppha‐H). The reactivities of alkylzinc phosphinate complexes toward H2O and O2 have also been investigated, which resulted in the isolation of two oxo‐zinc phosphinate clusters, that is, Zn4(μ4‐O)(dppha)6 and Zn4(μ4‐O)(dmppha)6, as well as the unique alkoxy(oxo)zinc cluster Zn4(μ4‐O)(μ2‐OtBu)(dppha)5. Analysis of the crystal structures has revealed that organozinc complexes incorporating phosphinate ligands exhibit a unique capacity for shape‐driven self‐assembly to produce extended networks, including noncovalent quasi‐porous materials. Finally, monodispersed and quantum‐sized ZnO NCs coated with phosphinate ligands have been prepared using a non‐external‐surfactant‐assisted wet‐chemical organometallic approach based on well‐defined RZn(O2PR′2)‐type compounds. The resulting brightly luminescent ZnO NCs exhibit average core sizes and hydrodynamic diameters in the ranges 2–4.5 nm and 5–8 nm, respectively. The size of the inorganic core is slightly affected by the character of the incorporated phosphinate ligand, being smallest for ZnO NCs coated by asymmetrically substituted mppha ligands. Regardless of whether or not various phosphinate coating ligands could be controllably applied on the ZnO NC surface, no significant differences were found in the luminescence profiles of the analyzed nanosystems.
Bright nanocrystals: We describe the synthesis of novel alkylzinc phosphinates and their use as efficient precursors of brightly luminescent ZnO nanocrystals coated with monoanionic organophosphorus ligands (see graphic).
Display omitted
•Bio-safe ligand-free and easily dispersible ZnO QDs were prepared by a novel organometallic strategy.•The process involves transformation of a DMSO solution of Et2Zn upon air ...exposition.•DMSO acts both as a solvent and a low-molecular-weight l-type surface protector.•The resulting QDs display unique long-term colloidal stability.•The developed method leads to the rational-by-design ZnO-based functional materials.
Colloidal quantum dots (QDs) are of widespread importance for their unique combination of physicochemical properties and a number of prospective applications, and the search for efficient synthetic methods to produce readily dispersible, functionally stable and ligand-free quantum dot-based inks is a vital and timely area of research. We describe a convenient room-temperature and non-external-surfactant-assisted organometallic synthetic strategy for the reproducible preparation of solution-processable organic ligand-free zinc oxide (ZnO) QDs. The process involves the controlled transformation of a DMSO solution of commercially available diethylzinc upon exposition towards atmospheric air, where H2O and O2 act simultaneously as oxygen sources, and DMSO acts both as a solvent and a low-molecular-weight l-type surface protector. The resulting QDs with a narrow size distribution (4.7 ± 0.8 nm) were comprehensively characterized with a combination of various analytical techniques, which nicely documented their unique stabilities when dried, precipitated, re-dissolved or exposed to air. Moreover, to substantiate idealized surface passivation of the resulting QDs, we investigated their stability in the biological environment and nano-specific activity toward selected normal and cancer cell lines, and no significant toxic effect was revealed. Undoubtedly, the reported one-step-one-pot organometallic approach paves the way to high-quality and bio-stable ZnO QDs coated by an easily and reversibly removable organic shell, auguring applications in a vast array of devices and nanomedicine.
The ability to utilize polluting gases in efficient metal‐mediated transformations is one of the most pressing challenges of modern chemistry. Despite numerous studies on the insertion of SO2 into ...M−C bonds, the chemical reaction of SO2 with organozinc compounds remains little explored. To fill this gap, we report here the systematic study of the reaction of Et2Zn towards SO2 as well as the influence of Lewis bases on the reaction course. Whereas the equimolar reaction provided a novel example of a structurally characterized organozinc ethylsulfinate compound of general formula (EtSO2)ZnEtn, the utilization of an excess of SO2 led to the formation of the zinc(II) bis(ethylsulfinate) compound (EtSO2)2Znn. Moreover, we have discovered that the presence of N‐donor Lewis bases represents an efficient tool for the preparation of extended zinc ethylsulfinates, which in turn led to the formation of 1D (EtSO2ZnEt)2(hmta)n and 2D ((EtSO2)2Zn)2(DABCO)n⋅solv (in which solv=THF or toluene, hmta= hexamethylenetetramine, and DABCO=1,4‐diazabicyclo2.2.2octane) coordination polymers, respectively. The results of DFT calculations on the reactivity of SO2 towards selected Zn−C reactive species as well as the role of an N‐donor Lewis base on the stabilization of the transition states complement the discussion.
Make a spider's web! We have investigated the stepwise insertion of SO2 into the Zn−C bonds of selected organozinc reagents, which leads to the formation of novel organozinc alkylsulfinates and represents an efficient tool for the preparation of extended zinc ethylsulfinate networks (see figure). The mechanism of SO2 insertion is discussed in detail on the basis of DFT calculations.
Zinc Oxide Nanocrystals
In article number 2309984, Gaël De Paëpe, Janusz Lewiński, and co‐workers synthesized ZnO nanocrystals (NCs) applying the standard sol‐gel synthetic protocol involving zinc ...acetate and lithium hydroxide, and tracked the integration of Li+ ions into NCs by combining various techniques. The study enabled determination of the structural imperfections and provided a new comprehensive look at the distribution of Li‐based species within the nanoparticles.
Spinning a zinc ethylsulfinate web using diethylzinc and sulfur dioxide! Systematic studies on the reactivity of Et2Zn towards: i) gaseous SO2, ii) gaseous SO2 with the assistance of urotropine ...(hmta), and iii) DABSO as a solid‐state source of SO2 are reported. These model reaction systems provide novel examples of structurally characterized molecular organozinc ethylsulfinates as well as represent efficient tools for the preparation of extended zinc ethylsulfinate networks. More information can be found in the Full Paper by A. Tulewicz, J. Lewiński et al. on page 14072.
Although an extraordinary amount of research into the chemistry of nanoscale zinc oxide (ZnO) has been conducted over the past three decades, application-driven design and reproducible fabrication of ...colloidal ZnO quantum dots (QDs) remain a great challenge. The application of low-molecular-weight, non-interfering protecting ligands may be potentially beneficial for the design of quantum-sized ZnO crystals, simultaneously providing colloidal stabilization and long-term functionality. Herein, we pursue the idea of '
less is more
' and continue our systematic investigations on a non-external-surfactant-assisted organometallic approach for the preparation of colloidal ZnO QDs
via
direct injection of Et
2
Zn to ligand-like solvent followed by exposition towards atmospheric air as well as we introduce a novel approach toward ZnO QDs through the transformation of sulfoxide-modulated Et
2
Zn-based precursors in a THF solution. The application of sulfoxides as L-type protectors contributes to the formation of uniform ZnO QDs with average diameters of 5.4 to 8.2 nm, depending of the character of applied sulfoxide, and the low surface grafting density of the coating ligand without impeding their colloidal as well as solid-state stability. The reported QDs exhibit almost identical absorption parameters and show particularly long, multiexponential PL decays reaching recombination times up to 2.3-2.8 μs. In turn, preliminary control experiments involving photodegradation of methylene blue demonstrate dramatically different photocatalytic performance of QDs derived from the neat ligand-like solvent synthesis and the new approach based on the finetuning of precursors' reactivity by Lewis-base chemical additives.
The introduction of low-molecular-weight L-type-protectors (
i.e.
, sulfoxides) in non-surfactant-assisted one-pot organometallic procedure leads to brightly luminescent and solution-processable ZnO QDs.
Less is More
In article number 2205909, Janusz Lewiński, Chang Kook Hong, and co‐workers demonstrate a novel approach to low‐temperature processable and inherently pure ZnO electron transport layer ...(ETL) for highly stable planar heterojunction perovskite solar cells (PSCs) based on organic ligand‐free ZnO quantum dots. The champion PSC achieved a power conversion efficiency of 20.05%, the state‐of‐the‐art performance among reported non‐passivated pure‐ZnO ETL‐based PSCs.
PDF
