Recent Progress on Cross-Linkable Fullerene-based Electron Transport Materials for Perovskite Solar Cells.

Fullerene-based derivatives are frequently used as electron transport materials (ETMs) and interface buffers for perovskite solar cells (PSCs) due to their excellent properties, including high electron affinity and mobility, low recombination energy, tunable energy levels, and solution processability. However, significant challenges arise because fullerene derivatives tend to aggregate and dimerize, which reduces exciton dissociation and charge transport capacity. Additionally, their chemical compatibility with perovskite absorbers facilitates halide diffusion and degradation of PSCs. This overlap causes delamination and dissolution during device fabrication, hindering the performance enhancement of fullerene-based PSCs. To address these issues, researchers have developed cross-linkable fullerene materials. These materials have been shown to not only significantly improve the power conversion efficiency (PCE) of PSCs but also effectively enhance the device stability. In this review, we summarized recent research progress on cross-linkable fullerene derivatives as ETMs for PSCs. We systematically analyze the impact of these cross-linked ETMs on device performance and long-term stability, focusing on their molecular structures and working mechanisms. Finally, we discuss the future challenges that need to be overcome to advance the application of cross-linkable fullerene materials in PSCs.

The superiority of isomeric, fluorination and curtailed π-conjunction on A-D-A type acceptors for organic photovoltaics.

The performance of organic solar cell (OSC) devices has been significantly enhanced by the dramatic evolution of A-D-A type non-fullerene acceptors (NFAs). Nevertheless, the structure-property-performance relationship of NFAs in the OSC device is unclear. Here, the intrinsic design factors of isomeric, fluorination and π-conjunction curtailing on the photophysical properties of benzodi (thienopyran) (BDTP) (named NBDTP-M, NBDTTP-M, NBDTP-Fin, and NBDTP-Fout)-based NFAs are discussed. The results show that fluorination on the terminal group of NBDTP-Fout could effectively decrease the highest occupied orbital (HOMO) energy level and the lowest unoccupied orbital (LUMO) energy level. And the long π-conjugated donor unit for NBDTTP-M could increase the HOMO energy level and bring a small HOMO-LUMO energy bandgap. Meanwhile, the substitution of external oxygen atoms and the fluorine atoms in the terminal group could introduce positive changes to the electrostatic potential of the NBDTP-Fout, favouring the charge separation at the donor/acceptor interface. Moreover, the structural design of external oxygen atom substitution, fluorination on the terminal group and curtailed π-conjugated donor unit could decrease the electron vibration-coupling of exciton diffusion, exciton dissociation and electronic transfer processes. The suppression of the exciton decay and charge recombination in those high-performance NFAs indicate that the investigated molecular designs could be effective for further improvement of OSCs.

C60 Fullerene-Induced Reduction of Metal Ions: Synthesis of C60-Metal Cluster Heterostructures with High Electrocatalytic Hydrogen-Evolution Performance.

Metal clusters, due to their small dimensions, contain a high proportion of surface atoms, thus possessing a significantly improved catalytic activity compared with their bulk counterparts and nanoparticles. Defective and modified carbon supports are effective in stabilizing metal clusters, however, the synthesis of isolated metal clusters still requires multiple steps and harsh conditions. Herein, we develop a C60 fullerene-driven spontaneous metal deposition process, where C60 serves as both a reductant and an anchor, to achieve uniform metal (Rh, Ir, Pt, Pd, Au and Ru) clusters without the need for any defects or functional groups on C60. Density functional theory calculations reveal that C60 possesses multiple strong metal adsorption sites, which favors stable and uniform deposition of metal atoms. In addition, owing to the electron-withdrawing properties of C60, the electronic structures of metal clusters are effectively regulated, not only optimizing the adsorption behavior of reaction intermediates but also accelerating the kinetics of hydrogen evolution reaction. The synthesized Ru/C60-300 exhibits remarkable performance for hydrogen evolution in an alkaline condition. This study demonstrates a facile and efficient method for synthesizing effective fullerene-supported metal cluster catalysts without any pretreatment and additional reducing agent.

Organic Chimeras Based on Selenosugars, Steroids, and Fullerenes as Potential Inhibitors of the ß-amyloid Peptide Aggregation.

The aggregation of ß-amyloid peptide (Aß) is associated with neurodegenerative diseases such as Alzheimer's disease (AD). Several therapies aimed at reducing the aggregation of this peptide have emerged as potential strategies for the treatment of AD. This paper describes the design and preparation of new hybrid molecules based on steroids, selenosugars, and [60]fullerene as potential inhibitors of Aß oligomerization. These moieties were selected based on their antioxidant properties and possible areas of interaction with the Aß. Cyclopropanations between C60 and malonates bearing different steroid and selenosugar moieties using the Bingel-Hirsch protocol have enabled the synthesis of functionalized molecular hybrids. The obtained derivatives were characterized by physical and spectroscopic techniques. Theoretical calculations for all the selenium compounds were performed using the density functional theory DFT/B3LYP-D3(BJ)/6-311G(2d,p) predicting the most stable conformations of the synthesized derivatives. Relevant geometrical parameters were investigated to relate the stereochemical behavior and the spectroscopic data obtained. The affinity of the compounds for Aß-peptide was estimated by molecular docking simulation, which predicted an increase in affinity and interactions for Aß for the hybrids containing the C60 core. In addition, parameters such as lipophilicity, polar surface area, and dipole moment were calculated to predict their potential interaction with membrane cells.

Synthesis and characterization of fullerene-based nanocarrier for targeted delivery of quercetin to the brain.

Aim: Preparation of quercetin fullerene conjugate (QFC) for nose-to-brain delivery and their in vitro and ex vivo characterizations.Methods: Carboxylated fullerene was converted into acetylated fullerene and quercetin was conjugated and physically adsorbed on acetylated fullerene.Results: The particle size and zeta potential of QFC and chitosan-coated QFC (CC-QFC) were found to be 179.2 ± 1.10, 293.4 ± 2.757, -5.28 ± 1.43 and 11.6 ± 0.4 respectively. The entrapment efficiency, loading efficiency of QFC were found to be 85.55% and 42.77%. The MTT assay revealed 80.69% SH-SY5Y cell viability at a concentration of 50 µg/ml. CC-QFC showed remarkable (89.20%) ex vivo mucoadhesive properties compared with QFC (66.67%). Further study showed no significant ciliotoxicity by CC-QFC.Conclusion: The obtained results suggested the potential of CC-QFC for treatment in Alzheimer's disease.

In our study, we developed a new method to deliver a natural substance called quercetin into the brain for the treatment of Alzheimer's disease. Quercetin is known for its health benefits, especially in protecting brain cells. We combined quercetin with a tiny carbon-based material called fullerene, which looks like a soccer ball, to create a new compound called quercetin fullerene conjugate (QFC). This QFC was designed to help quercetin reach the brain more effectively. To make it even better at reaching the brain, we coated QFC with a substance called chitosan. Coating it with chitosan can help to adhere it to nasal cavity for longer time for the delivery of quercetin to the brain. Importantly, our studies showed that this modified form of quercetin did not harm brain cells or the lining of the nose.Overall, our findings suggest that this new approach could be a promising way to develop treatments for Alzheimer's disease.

Efficient and Stable Inverted Perovskite Solar Cells Enabled by a Fullerene-Based Hole Transport Molecule.

Designing an efficient modification molecule to mitigate non-radiative recombination at the NiOx/perovskite interface and improve perovskite quality represents a challenging yet crucial endeavor for achieving high-performance inverted perovskite solar cells (PSCs). Herein, we synthesized a novel fullerene-based hole transport molecule, designated as FHTM, by integrating C60 with 12 carbazole-based moieties, and applied it as a modification molecule at the NiOx/perovskite interface. The in-situ self-doping effect, triggered by electron transfer between carbazole-based moiety and C60 within the FHTM molecule, along with the extended π conjugated moiety of carbazole groups, significantly enhances FHTM's hole mobility. Coupled with optimized energy level alignment and enhanced interface interactions, the FHTM significantly enhances hole extraction and transport in corresponding devices. Additionally, the introduced FHTM efficiently promotes homogeneous nucleation of perovskite, resulting in high-quality perovskite films. These combined improvements led to the FHTM-based PSCs yielding a champion efficiency of 25.58% (Certified: 25.04%), notably surpassing that of the control device (20.91%). Furthermore, the unencapsulated device maintained 93% of its initial efficiency after 1000 hours of maximum power point tracking under continuous one-sun illumination. This study highlights the potential of functionalized fullerenes as hole transport materials, opening up new avenues for their application in the field of PSCs.

Nonfullerene Acceptors Bearing Spiro-Substituted Bithiophene Units in Organic Solar Cells: Tuning the Frontier Molecular Orbital Distribution to Reduce Exciton Binding Energy.

The development of nonfullerene acceptors (NFAs), represented by ITIC, has contributed to improving the power conversion efficiency (PCE) of organic solar cells (OSCs). Although tuning the electronic structures to reduce the exciton binding energy (Eb) is considered to promote photocharge generation, a rational molecular design for NFAs has not been established. In this study, we designed and developed two ITIC-based NFAs bearing spiro-substituted bithiophene or biphenyl units (named SpiroT-DCI and SpiroF-DCI) to tune the frontier molecular orbital (FMO) distribution of NFAs. While the highest occupied molecular orbitals (HOMOs) of SpiroF-DCI and ITIC are delocalized in the main π-conjugated framework, the HOMO of SpiroT-DCI is distributed on the bithiophene unit. Reflecting this difference, SpiroT-DCI exhibits a smaller Eb than either SpiroF-DCI or ITIC, and exhibits greater external quantum efficiency in single-component OSCs. Furthermore, SpiroT-DCI shows improved PCEs for bulk-heterojunction OSCs with a donor of PBDB-T, compared with that of either SpiroT-DCI or ITIC. Time-resolved spectroscopy measurements show that the photo-induced intermolecular charge separation is effective even in pristine SpiroT-DCI films. This study highlights the introduction of spiro-substituted bithiophene units that are effective in tuning the FMOs of ITIC, which is desirable for reducing the Eb and improving the PCE in OSCs.

Direct Solution Deposition of Large-Area Non-Solvated Fullerene Single-Crystal Films for High-Performance n-Type Field-Effect Transistors.

Fullerene (C60) crystals have attracted considerable attention in the field of optoelectronic devices owing to their excellent performance as n-type semiconductor material. However, a challenge still remains unbeaten as to the continuous crystallization of non-solvated C60 single-crystal films with high coverage and uniform alignment using low-cost solution techniques. Here, a facile bar coating method is used to prepare ribbon-shaped non-solvated C60 crystals with a large area (up to centimeters) and high coverage (>95%) by precisely controlling the crystallization process from specific solvents. Benefiting from the non-solvated crystalline structure, well-distributed thickness, uniform morphological alignment, and crystallographic orientation, organic field-effect transistors fabricated from the C60 single-crystal films exhibit a high average electron mobility of 2.28 cm2 V-1s-1, along with the coefficient of variance (CV) as small as 13.6%. This efficient manufacturing method will lay a strong foundation for C60 single-crystal films to fit into the future high-performance integrated optoelectronic application.

Investigation the behavior of different fullerenes on graphene surface.

In the present study, the regime of motion of fullerene molecules on graphene substrate in a specific temperature range is investigated. The potential energy of fullerene molecules is analyzed using classical molecular dynamics methods. Fullerene molecules C36, C50, C60, C76, C80, and C90 are selected due to spherical shapes of different sizes and good motion performance in previous studies. Analysis of the motion regime at different temperatures is one of the main objectives of this study. To achieve this aim, the translational and rotational movements of fullerene molecules are studied independently. In the first step of the investigation, Lennard-Jone's potential energy of fullerene molecules is calculated. Subsequently, the motion regime of different fullerenes is classified based on their displacement and diffusion coefficient. Findings indicate C60 is not appropriate in all conditions. However, C90 and C76 molecules are found to be appropriate candidates in most cases in different conditions. As far as a straight-line movement is considered, the deviation of fullerene molecules is compared by their angular velocities. Although C60 has a lower angular velocity due to its symmetrical shape, it may not move well due to its low diffusion coefficient. Overall, our study helps to understand the performance of different fullerene molecules on graphene substrate and find their possible applications, especially as wheels in nanomachine or nanocarrier structures.

Effect of C60 Fullerene on Muscle Injury-Induced Rhabdomyolysis and Associated Acute Renal Failure.

Introduction: Rhabdomyolysis, as an acute stage of myopathy, causes kidney damage. It is known that this pathology is caused by the accumulation of muscle breakdown products and is associated with oxidative stress. Therefore, the present study evaluated the effect of intraperitoneal administration (dose 1 mg/kg) of water-soluble C60 fullerenes, as powerful antioxidants, on the development of rat kidney damage due to rhabdomyolysis caused by mechanical trauma of the muscle soleus of different severity (crush syndrome lasting 1 min under a pressure of 2.5, 3.5, and 4.5 kg/cm2, respectively). Methods: Using tensometry, biochemical and histopathological analyses, the biomechanical parameters of muscle soleus contraction (contraction force and integrated muscle power), biochemical indicators of rat blood (concentrations of creatinine, creatine phosphokinase, urea and hydrogen peroxide, catalase and superoxide dismutase activity), glomerular filtration rate and fractional sodium excretion value, as well as pathohistological and morphometric features of muscle and kidney damages in rats on days 1, 3, 6 and 9 after the initiation of the injury were studied. Results: Positive changes in biomechanical and biochemical parameters were found during the experiment by about 27-30 ± 2%, as well as a decrease in pathohistological and morphometric features of muscle and kidney damages in rats treated with water-soluble C60 fullerenes. Conclusion: These findings indicate the potential application of water-soluble C60 fullerenes in the treatment of pathological conditions of the muscular system caused by rhabdomyolysis and the associated oxidative stress.

First-principles study of electrochemical H2O2 production on Pd-B40 single-atom catalyst.

Hydrogen peroxide (H2O2), a versatile green compound, is increasingly in demand. The electrochemical two-electron oxygen reduction reaction (2e- ORR) is a simple and environmentally friendly substitute method to the traditional anthraquinone oxidation method for H2O2 production. This study systematically investigates the 2e- ORR process on single transition metal atom-loaded boron fullerene (M - B40) using density functional theory calculations. In evaluating the stability of the catalysts, we found that Au, Pd, Pt, Rh, and Ir atoms adsorbed on hexagonal or heptagonal sites of B40 exhibit good stability. Among these, Pd-modified B40 heptagonal cavity (Pd-B40-heptagonal) demonstrates an ideal Gibbs free energy change for OOH* (4.49 eV) and efficiently catalyzes H2O2 production at a low overpotential (0.27 V). Electronic structure analysis reveals that electron transfer between Pd-B40-heptagonal and adsorbed O2 facilitates O2 activation. Additionally, the high 2e- ORR activity of Pd-B40-heptagonal is attributed to electron transfer from the Pd-d orbitals to the π* anti-bonding of p orbitals of OOH*, moderately activating the O-O bond. This study offers valuable understanding designing high-performance electrocatalysts for 2e- ORR.

Interpenetrated Donor-Acceptor Heterojunctions in 2D Conjugated Dibenzo[g,p]chrysene-Based Kagome Covalent Organic Frameworks.

Dibenzo[g,p]chrysene can be viewed as a constrained propeller-shaped tetraphenylethylene with reduced curvature and has been utilized to construct dual-pore kagome covalent organic frameworks (COFs) with tightly packed two-dimensional (2D) layers owing to its rigid and more planar structural characteristics. Here, we introduce 2D COFs based on the node 4,4',4″,4‴-(dibenzo[g,p]chrysene-2,7,10,15-tetraphenyl)tetraamine (DBCTPTA) featuring extended conjugation compared to the dibenzo[g,p]chrysene-3,6,11,14-tetraamine (DBCTA) node. We establish two exceptionally crystalline imine-linked 2D COFs with a hexagonal dual-pore kagome structure based on the DBCTPTA core. The newly synthesized thienothiophene (TT) and benzodithiophene (BDT)-based DBCTPTA COFs show a tight stacking behavior between adjacent layers. Furthermore, we obtained an unprecedented, interpenetrated electron-donor/acceptor host-guest system with an electron-donating BDT DBCTPTA COF synthesized in situ with the soluble fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) serving as molecular acceptor. The BDT DBCTPTA COF@PCBM film shows a much shorter amplitude-averaged PL lifetime of 7 ± 2 ps compared to 30 ± 4 ps of the BDT DBCTPTA COF film, indicating the light-induced charge transfer process. The successful in situ formation of interpenetrated donor-acceptor heterojunctions within 2D COFs offers a promising strategy for establishing D-A heterojunctions in diverse framework materials with open channel systems.

Exploration of the effect of multiple acceptor and π-spacer moieties coupled to indolonaphthyridine core for promising organic photovoltaic properties: a first principles framework.

Herein, the indolonaphthyridine-based molecules (INDTD1-INDTD8) with A1-π-A2-π-A1 configuration were designed by the end-capped modification of INDTR reference with various acceptors. The density functional theory (DFT) and time-dependent DFT (TD-DFT) analyses at M06/6-31G(d,p) level were reported in this research to explore their optoelectronic and photovoltaic features. Their geometrical structures were initially optimized at the afore-said level and followed by various calculations such as the frontier molecular orbitals (FMOs), UV-Visible, density of states (DOS), transition density matrix (TDM), binding energy (Eb), open circuit voltage (Voc) and fill factor (FF). Moreover, their global reactivity parameters (GRPs) were depicted by using the HOMO-LUMO band gaps obtained from the FMOs study. The tailored molecules demonstrated lower band gaps (2.183-2.269 eV) than INDTR (2.288 eV). They also showed bathochromic shifts in the visible region in chloroform (735.937-762.318 nm) and gas phase (710.384-729.571 nm) as compared to INDTR (724.710 and 698.498 nm, respectively). Further, intramolecular charge transfer (ICT) was demonstrated via the DOS and TDM graphical maps. Among all the entitled chromophores, INDTD7 showed significantly reduced band gap (2.183 eV), red-shifted absorption value (760.914 nm) in chloroform solvent and minimal Eb value (0.554 eV). The presence of -SO3H groups on the terminal acceptors of INDTD7  may enhance the mobility of charges. The results suggested that the newly designed chromophores can be effective candidates for the future organic solar cell applications. Moreover, this study may encourage the experimentalists to develop photovoltaic materials.

Sensitive SWIR Organic Photodetectors with Spectral Response Reaching 1.5 µm.

The performance of organic photodetectors (OPDs) sensitive to the short-wavelength infrared (SWIR) light lags behind commercial indium gallium arsenide (InGaAs) photodetectors primarily due to the scarcity of organic semiconductors with efficient photoelectric responses exceeding 1.3 µm. Limited by the Energy-gap law, ultralow-bandgap organic semiconductors usually suffer from severe non-radiative transitions, resulting in low external quantum efficiency (EQE). Herein, a difluoro-substituted quinoid terminal group (QC-2F) with exceptionally strong electron-negativity is developed for constructing a new non-fullerene acceptor (NFA), Y-QC4F with an ultralow bandgap of 0.83 eV. This subtle structural modification significantly enhances intermolecular packing order and density, enabling an absorption onset up to 1.5 µm while suppressing non-radiation recombination in Y-QC4F films. SWIR OPDs based on Y-QC4F achieve an impressive detectivity (D*) over 1011 Jones from 0.4 to 1.5 µm under 0 V bias, with a maximum of 1.68 × 1012 Jones at 1.16 µm. Furthermore, the resulting OPDs demonstrate competitive performance with commercial photodetectors for high-quality SWIR imaging even under 1.4 µm irradiation.

One-Stone-For-Three-Birds Strategy Using a Fullerene Modifier for Efficient and Stable Inverted Perovskite Solar Cells.

The electron extraction from perovskite/C60 interface plays a crucial role in influencing the photovoltaic performance of inverted perovskite solar cells (PSCs). Here, we develop a one-stone-for-three-birds strategy via employing a novel fullerene derivative bearing triple methyl acrylate groups (denoted as C60-TMA) as a multifunctional interfacial layer to optimize electron extraction at the perovskite/C60 interface. It is found that the C60-TMA not only passivates surface defects of perovskite via coordination interactions between C=O groups and Pb2+ cations but also bridge electron transfer between perovskite and C60. Moreover, it effectively induces the secondary grain growth of the perovskite film through strong bonding effect, and this phenomenon has never been observed in prior art reports on fullerene related studies. The combination of the above three upgrades enables improved perovskite film quality with increased grain size and enhanced crystallinity. With these advantages, C60-TMA treated PSC devices exhibit a much higher power conversion efficiency (PCE) of 24.89% than the control devices (23.66%). Besides, C60-TMA benefits improved thermal stability of PSC devices, retaining over 90% of its initial efficiency after aging at 85 °C for 1200 h, primarily due to the reinforced interfacial interactions and improved perovskite film quality.

A regulatory compliant short-term oral toxicity study of soluble [60]fullerenes in rats.

Thirty-eight years after its discovery, the safety of [60]fullerene (C60), the most abundant fullerene with many potential applications, particularly in oxidative stress-related medicine, remains controversial. This is mainly due to the alleged dangers of C60 nanomaterial, which are regularly supported by some publications. While several academic studies have confirmed the safety of C60 in various experimental models, it is well known that C60 aggregates can carry toxic elements. Meanwhile, countless websites offer C60-oily solutions to consumers, without any regulatory consideration. Therefore, an officially certified toxicity study is urgently needed to avoid any public health problems. In this context, we report on the first certified short-term oral toxicity study of soluble C60, designed according to the guidelines of the Organization for Economic Cooperation and Development, with a deviation in the duration (2 weeks instead of 4 weeks) accepted by the U.S. Food and Drug Administration. The results of this study, conducted in an independent accredited European Laboratory, clearly show that C60 in soluble form (0.8 mg/ml of extra virgin olive oil), administered at the highest possible dose of 3.8 mg/kg body weight/day, did not cause any adverse effects in rats after 14 days of daily oral administration. This report should settle the debate on the acute oral toxicity of C60 and pave the way for further preclinical studies. The study is accompanied by a comprehensive report that includes documentation of the raw data.

С60 fullerene protective effect against the rat muscle soleus trauma.

Muscle trauma is one of the most common body injuries. Severe consequences of muscle trauma are ischemic injuries of the extremities. It is known that the intensification of free radical processes takes place in almost most acute diseases and conditions, including muscle trauma. C60 fullerene (C60) with powerful antioxidant properties can be considered a potential nanoagent for developing an effective therapy for skeletal muscle trauma. Here the water-soluble C60 was prepared and its structural organization has been studied by the atomic force microscopy and dynamic light scattering techniques. The selective biomechanical parameters of muscle soleus contraction and biochemical indicators of blood in rats were evaluated after intramuscular injection of C60 1 h before the muscle trauma initiation. Analysis of the force muscle response after C60 injection (1 mg kg-1 dose) showed its protective effect against ischemia and mechanical injury at the level of 30 ± 2 % and 17 ± 1 %, accordingly, relative to the pathology group. Analysis of biomechanical parameters that are responsible for correcting precise positioning confirmed the effectiveness of C60 at a level of more than 50 ± 3 % relative to the pathology group. Moreover, a decrease in the biochemical indicators of blood by about 33 ± 2 % and 10 ± 1 % in ischemia and mechanical injury, correspondingly, relative to the pathology group occurs. The results obtained demonstrate the ability of C60 to correct the functional activity of damaged skeletal muscle.

Influence of fullerene content on the properties of polyurethane resins: A study of rheology and thermal characteristics.

The effect of different contents of fullerene on the properties of polyurethane resins (PUs), including rheology and thermal properties, was investigated. Polyurethane resins were prepared through polyaddition reactions using different isocyanate monomers such as isophorone diisocyanate (IPDI), methylene diphenyl diisocyanate (MDI), hexamethylene diisocyanate (HDI), and different polyols, such as poly(oxytetramethylene) glycol (PTMG), the triol trade name FA-703, and polypropylene glycols (PPG), at an NCO/OH ratio 0.94 and a temperature of 100 °C. IR spectroscopy was used to control the polymerization of PUs through the shifting of NCO peaks. The results showed that the rheology and thermal properties of the prepared PU resins depend on the type of isocyanates and fullerene used. Based on the type of isocyanates, the PU resin prepared by MDI has the highest viscosity and thermal stability compared to the other isocyanates investigated. On the other hand, the PU resins prepared by IPDI mixed with fullerene had the highest viscosity and thermal stability. However, the initial decomposition temperature (T onset) of the PUs decreased with the addition of fullerene without affecting the maximum decomposition temperature (PDT max) of the PU resin.

Exohedral Diels-Alder Reactivity of Endohedral Metallofullerene C36.

Understanding the exohedral reactivity of metallofullerenes is crucial for its application in various fields. By systematically controlling the trapped species inside the fullerene its reactivity can be tamed. In this work we report the preferential position of 3d metal atoms inside the C36 cage and their effect on exohedral reactivity in comparison with the neutral and the dianionic cage. The Diels-Alder (DA) reaction between butadiene and all non-equivalent [5-5], [6-5] and [6-6] C-C bonds on the fullerene cage was considered for the analysis, by using density functional theory at the S12g/TZ2P level including COSMO solvation model to elucidate the complete mechanistic pathways. Our results indicate that the preferential position of the metal ion is at the position close to the upper hexagon, and that the general trend in the reactivity of bonds follows the order [5-5] > [6-5] > [6-6]. Moreover, the encapsulation of metal atoms further enhances the reactivity of these bonds, by distorting the system and delocalizing the LUMOs all over the cage.

Suppressed Defects by Functional Thermally Cross-Linked Fullerene for High-Efficiency Tin-Lead Perovskite Solar Cells.

Mixed tin-lead (Sn-Pb) perovskites have attracted the attention of the community due to their narrow bandgap, ideal for photovoltaic applications, especially tandem solar cells. However, the oxidation and rapid crystallization of Sn2+ and the interfacial traps hinder their development. Here, cross-linkable [6,6]-phenyl-C61-butyric styryl dendron ester (C-PCBSD) is introduced during the quenching step of perovskite thin film processing to suppress the generation of surface defects at the electron transport layer interface and improve the bulk crystallinity. The C-PCBSD has strong coordination ability with Sn2+ and Pb2+ perovskite precursors, which retards the crystallization process, suppresses the oxidation of Sn2+, and improves the perovskite bulk and surface crystallinity, yielding films with reduced nonradiative recombination and enhanced interface charge extraction. Besides, the C-PCBSD network deposited on the perovskite surface displays superior hydrophobicity and oxygen resistance. Consequently, the devices with C-PCBSD obtain PCEs of up to 23.4% and retained 97% of initial efficiency after 2000 h of storage in a N2 atmosphere.