Efficient Tin-Based Perovskite Solar Cells Enabled by Precisely Synthesized Single-Isomer Fullerene Bisadducts with Regulated Molecular Packing.

Designing and synthesizing fullerene bisadducts with a higher-lying conduction band minimum is promising to further improve the device performance of tin-based perovskite solar cells (TPSCs). However, the commonly obtained fullerene bisadduct products are isomeric mixtures and require complicated separation. Moreover, the isomeric mixtures are prone to resulting in energy alignment disorders, interfacial charge loss, and limited device performance improvement. Herein, we synthesized single-isomer C60- and C70-based diethylmalonate functionalized bisadducts (C60BB and C70BB) by utilizing the steric-hindrance-assisted strategy and determined all molecular structures involved by single crystal diffraction. Meanwhile, we found that the different solvents used for processing the fullerene bisadducts can effectively regulate the molecular packing in their films. The dense and amorphous fullerene bisadduct films prepared by using anisole exhibited the highest electron mobility. Finally, C60BB- and C70BB-based TPSCs showed impressive efficiencies up to 14.51 and 14.28%, respectively. These devices also exhibited excellent long-term stability. This work highlights the importance of developing strategies to synthesize single-isomer fullerene bisadducts and regulate their molecular packing to improve TPSCs' performance.

Perovskite light-emitting diodes with external quantum efficiency exceeding 20 per cent.

Metal halide perovskite materials are an emerging class of solution-processable semiconductors with considerable potential for use in optoelectronic devices1-3. For example, light-emitting diodes (LEDs) based on these materials could see application in flat-panel displays and solid-state lighting, owing to their potential to be made at low cost via facile solution processing, and could provide tunable colours and narrow emission line widths at high photoluminescence quantum yields4-8. However, the highest reported external quantum efficiencies of green- and red-light-emitting perovskite LEDs are around 14 per cent7,9 and 12 per cent8, respectively-still well behind the performance of organic LEDs10-12 and inorganic quantum dot LEDs13. Here we describe visible-light-emitting perovskite LEDs that surpass the quantum efficiency milestone of 20 per cent. This achievement stems from a new strategy for managing the compositional distribution in the device-an approach that simultaneously provides high luminescence and balanced charge injection. Specifically, we mixed a presynthesized CsPbBr3 perovskite with a MABr additive (where MA is CH3NH3), the differing solubilities of which yield sequential crystallization into a CsPbBr3/MABr quasi-core/shell structure. The MABr shell passivates the nonradiative defects that would otherwise be present in CsPbBr3 crystals, boosting the photoluminescence quantum efficiency, while the MABr capping layer enables balanced charge injection. The resulting 20.3 per cent external quantum efficiency represents a substantial step towards the practical application of perovskite LEDs in lighting and display.

Changes in microcystin concentration in Lake Taihu, 13 years (2007-2020) after the 2007 drinking water crisis.

Since the 2007 water crisis occurred in Lake Taihu, substantial measures have been taken to restore the lake. This study evaluates the effectiveness of these restoration activities. We examined the physicochemical parameters and the distribution of microcystin and Microcystis in both the water column and sediment during the bloom period of May 2020 to October 2020. The mean value of extracellular and intracellular microcystin content was 0.12 µg L-1 and 16.26 µg L-1, respectively. The mean value of microcystin in sediment was 172.02 ng g-1 and peaked in August. The concentration in the water and sediment was significantly lower than the historical average concentration. The abundance of toxigenic Microcystis and total Microcystis in the water column ranged from 2.61 × 102 to 2.25 × 109 copies·L-1 and 8.28 × 105 to 2.76 × 109 copies·L-1, respectively. The proportion of toxic Microcystis in the sediment ranging from 31.2% to 19.12%. The highest and lowest region was Meiliang Bay and Grass-algae type zone, respectively. The copy number of the 16S rRNA gene was 1-4 orders of magnitude higher than that of mcyA gene in populations of Microcystis, indicating that non-toxic Microcystis was the dominant form in the majority of the lake. The abundance of toxic Microcystis in the water column was positively correlated with total phosphorus, PO43--P and pH, while the water temperature played distinct role to the distribution of toxic Microcystis in sediment. Our research indicated phosphorus remains a key factor influencing the toxic Microcystis and microcystins in the water column. pH played distinct roles in the distribution of microcystins in sediment and water column. The increasing water temperature is a threat. Explicit management actions and policies, which take into account nutrient concentrations, pH, and increasing temperatures, are necessary to understand and control the distribution of microcystin and Microcystis in Lake Taihu.

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.

Cross-Linkable Fullerene Enables Elastic and Conductive Grain Boundaries for Efficient and Wearable Tin-Based Perovskite Solar Cells.

Tin-based perovskite solar cells (TPSCs) have received increasing attention due to their low toxicity, high theoretical efficiency, and potential applications as wearable devices. However, the inherent fast and uncontrollable crystallization process of tin-based perovskites results in high defect density in the film. Meanwhile, when fabricated into flexible devices, the prepared perovskite film exhibits inevitable brittleness and high Young's modulus, seriously weakening the mechanical stability. In this work, we design and synthesize a cross-linkable fullerene, thioctic acid functionalized C60 fulleropyrrolidinium iodide (FTAI), which has multiple interactions with perovskite components and can finely regulate the crystallization quality of perovskite film. The obtained perovskite film shows an increased grain size and a more matched energy level with the electron transport material, effectively improving the carrier extraction efficiency. The FTAI-based rigid device achieves a champion efficiency of 14.91 % with enhanced stability. More importantly, the FTAI located at the perovskite grain boundaries could spontaneously cross-link during the perovskite annealing process, which effectively improves the conductivity and elasticity of grain boundaries, thereby giving the film excellent bending resistance. Finally, the FTAI-based wearable device yields a record efficiency of 12.35 % and displays robust bending durability, retaining about 90 % of the initial efficiency after 10,000 bending times.

Different environmental factors drive the concentrations of microcystin in particulates, dissolved water, and sediments peaked at different times in a large shallow lake.

Global distribution and health threats of microcystins (MCs) have received much more attention, but there are still significant knowledge gaps in the peak periods and driving factors of MC in different phases of freshwater ecosystems. Thus, we systematically analyzed the annual variation of different MC congeners (-LR, -RR, and -YR, where L, R, and Y respectively represent leucine, arginine, and tyrosine) in particulates, dissolved water, and sediments in three eutrophic bays of Lake Taihu, China. The results indicated that particulate MCs concentration was the highest, followed by dissolved and sediment MC, with the mean concentration of 7.58 µg/L, 1.48 µg/L, and 0.15 µg/g (DW), respectively. Except for particulate MC, the concentrations of the other two types of MC showed significant differences among the three bays. The dominant congeners of the three types of MCs were different, with the highest proportion of MC-LR being observed in sediment MCs and the lowest in particulate MCs. The peak period of the three types of MC was also different, with particulate MCs reaching their peak in July and October, dissolved MCs in May to July and October, and sediment MCs reaching their peak in September. Consistent with our hypothesis, the dynamics of different types of MCs were driven by different environmental factors. Particulate MCs were primarily related to biological parameters, followed by TP and dissolved carbon. By contrast, dissolved MCs strongly correlated with water temperature and dissolved oxygen. While sediment MCs were primarily driven by properties of sediments, followed by different forms of nitrogen in the water column. Our results suggested that particulate and dissolved MCs in northern Lake Taihu pose high health threats, especially in the peak period. Moreover, a more detailed and targeted risk management strategy should be designed to prevent the possible hazards posed by different types of MC.

Risk assessment and identification of factors influencing the historical concentrations of microcystin in Lake Taihu, China.

Understanding the history of microcystins (MCs) pollution in large lakes can help inform future lake management. We collected sediment cores from Lake Taihu to: investigate the long-term record of MCs (MC-LR, MC-YR, and MC-RR), explore the main environmental drivers of MCs, and assess their public health and ecological risks. Results showed that MCs content in all cores increased over time. The core from north Taihu had the highest MC concentrations, with an average total MCs (sum of MC-LR, MC-YR, and MC-RR = TMCs) content of (74.31±328.55) ng/g. The core from eastern Taihu showed the lowest average TMCs content of (2.91±3.95) ng/g. PCA showed that sediment MCs at the three sites were positively correlated with sediment chlorophyll-a. MC-LR and MC-YR in northern and western Taihu negatively correlated with both the sediment total organic carbon/sediment total nitrogen ratio (STOC/STN) and water nitrate (NO3--N) concentration, but three MC congeners at eastern Taihu showed positive correlations with water orthophosphate (PO43--P), NO3--N, and STOC/STN. Generalized additive model analysis at each site revealed that NO3--N was the main TMCs driver in northern and western Taihu where phytoplankton dominated, whereas PO43--P was the main TMCs driver in eastern Taihu where macrophytes dominated. At the whole lake scale, total phosphorus (TP) and PO43--P were the most important environmental drivers influencing MCs; TP explained 47.4%, 44.2%, and 47.6% while orthophosphate explained 34.8%, 31.2%, and 34.7% of the deviance on TMCs, MC-LR, and MC-YR, respectively. NO3--N also showed a strong effect on MCs variation, especially on MC-YR. Risk assessment showed that both ecological and public health risk has increased in recent years. We conclude that while control of phosphorus and nitrogen input should be a major focus for future lake management, lake zone-specific management strategies may also be important.

Acute and chronic toxicity of microcystin-LR and phenanthrene alone or in combination to the cladoceran (Daphnia magna).

Hazardous substances, such as microcystin-LR (MC-LR) and phenanthrene (Phe) are ubiquitous co-contaminants in eutrophic freshwaters, which cause harms to aquatic organisms. However, the risks associated with the co-exposure of aquatic biota to these two chemicals in the environment have received little attention. In this study, the single and mixture toxic effects of MC-LR and Phe mixtures were investigated in Daphnia magna after acute and chronic exposure. Acute tests showed that the median effective concentrations (48 h) for MC-LR, Phe and their mixtures were 13.46, 0.57 and 8.84 mg/L, respectively. Mixture toxicity prediction results indicated that the independent action model was more applicable than the concentration addition model. Moreover, combination index method suggested that the mixture toxicity was concentration dependent. Synergism was elicited at low concentrations of MC-LR and Phe exposure (≤4.04 + 0.17 mg/L), whereas antagonistic or additive effects were induced at higher concentrations. The involved mechanism of antagonism was presumably attributable to the protective effects of detoxification genes activated by high concentrations of MC-LR in mixtures. Additionally, chronic results also showed that exposure to a MC-LR and Phe mixture at low concentrations (≤50 +2 µg/L) resulted in greater toxic effects on D. magna life history than either chemical acting alone. The significant inhibition on detoxification genes and increased accumulation of MC-LR could be accounted for their synergistic toxic effects on D. magna. Our findings revealed the exacerbated ecological hazard of MC-LR and Phe at environmental concentrations (≤50 +2 µg/L), and provided new insights to the potential toxic mechanisms of MC-LR and Phe in aquatic animals.

Efficient and Stable Low-Bandgap Perovskite Solar Cells Enabled by a CsPbBr3-Cluster Assisted Bottom-up Crystallization Approach.

Recently, low-bandgap formamidinium lead iodide FAPbI3-based perovskites are of particular interest for high-performance perovskite solar cells (PSCs) due to their broad spectral response and high photocurrent output. However, to inhibit the spontaneous α-to-δ phase transition, 15-17% (molar ratio) of bromide and cesium or methylammonium incorporated into the FAPbI3 are indispensable to achieve efficient PSCs. In return, the high bromide content will increase bandgap and narrow the spectral response region. If simply reducing the bromide content, the corresponding PSCs exhibit inferior operational stability due to α-to-δ phase transition, interface degradation, and halide migration. Herein, we report a CsPbBr3-cluster assisted vertically bottom-up crystallization approach to fabricate low-bromide (1% ∼ 6%), α-phase pure, and MA-free FAPbI3-based PSCs. The clusters, in the size of several nanometers, could act as nuclei to facilitate vertical growth of high quality α-FAPbI3 perovskite crystals. Moreover, these clusters can show further intake by perovskite after thermal annealing, which improves the phase homogeneity of the as-prepared perovskite films. As a result, the corresponding mesoporous PSCs deliver a champion efficiency of 21.78% with photoresponse extended to 830 nm. Moreover, these devices show remarkably improved operational stability, retaining ∼82% of the initial efficiency after 1,000 h of maximum power point tracking under 1 sun condition.

Toward Long-Term Stability: Single-Crystal Alloys of Cesium-Containing Mixed Cation and Mixed Halide Perovskite.

Perovskite solar cells are strong competitors for silicon-based ones, but suffer from poor long-term stability, for which the intrinsic stability of perovskite materials is of primary concern. Herein, we prepared a series of well-defined cesium-containing mixed cation and mixed halide perovskite single-crystal alloys, which enabled systematic investigations on their structural stabilities against light, heat, water, and oxygen. Two potential phase separation processes are evidenced for the alloys as the cesium content increases to 10% and/or bromide to 15%. Eventually, a highly stable new composition, (FAPbI3)0.9(MAPbBr3)0.05(CsPbBr3)0.05, emerges with a carrier lifetime of 16 µs. It remains stable during at least 10 000 h water-oxygen and 1000 h light stability tests, which is very promising for long-term stable devices with high efficiency. The mechanism for the enhanced stability is elucidated through detailed single-crystal structure analysis. Our work provides a single-crystal-based paradigm for stability investigation, leading to the discovery of stable new perovskite materials.

Combined toxic effects of microcystin-LR and phenanthrene on growth and antioxidant system of duckweed (Lemna gibba L.).

Microcystins and polycyclic aromatic hydrocarbons commonly co-exist in eutrophic freshwater environments. However, their combined toxicity remains unknown. The aim of this study was to evaluate the combined toxic effects of microcystin-LR (MC-LR) and phenanthrene (Phe) on duckweed (Lemna gibba L.) during a short-term exposure (7 d). L. gibba was exposed to a range of environmentally relevant concentrations of MC-LR (5, 50, 250, 500 µg/L) and Phe (0.1, 1, 5, 10 µg/L), both individually and in MC-LR + Phe mixtures (5 + 0.1, 50 + 1, 250 + 5, 500 + 10 µg/L). Subsequently, biomarkers of toxicity such as growth, chlorophyll-a, and antioxidant enzyme activity (catalase, superoxide dismutase, and peroxidase) were analyzed in L. gibba. Growth and the antioxidant system of L. gibba were not significantly inhibited by Phe alone, whereas higher concentrations of individual MC-LR (≥50 µg/L) significantly inhibited growth and induced oxidative stress. Based on Abott's formula, their interaction effects were concentration dependent. Antagonistic effects were observed when exposed to combinations of lower concentrations of MC-LR and Phe (≤50 + 1 µg/L), while additive or synergistic effects were induced at higher concentrations of both compounds (≥250 + 5 µg/L). Moreover, higher concentrations of Phe (≥5 µg/L) increased the accumulation of MC-LR in L. gibba. Our results suggested that the toxic effects of MC-LR and phenanthrene were exacerbated only when they co-exist in water bodies at relatively high concentrations. Consequently, co-existence of MC-LR and Phe at low levels are unlikely to exacerbate ecological hazards to L. gibba in most aquatic environments, at least based on responses of this plant.

Effect of microcystins on root growth, oxidative response, and exudation of rice (Oryza sativa).

A 30 days indoor hydroponic experiment was carried out to evaluate the effect of microcystins (MCs) on rice root morphology and exudation, as well as bioaccumulation of MCs in rice. MCs were bioaccumulated in rice with the greatest concentrations being observed in the leaves (113.68µgg-1 Fresh weight (FW)) when exposed to 500µgL-1 MCs. Root activity at 500µgL-1 decreased 37%, compared to the control. MCs also induced disruption of the antioxidant system and lipid peroxidation in rice roots. Root growth was significantly inhibited by MCs. Root weight, length; surface area and volume were significantly decreased, as well as crown root number and lateral root number. After 30 days exposure to MCs, an increase was found in tartaric acid and malic acid while the other organic acids were not affected. Glycine, tyrosine, and glutamate were the only amino acids stimulated at MCs concentrations of 500µgL-1. Similarly, dissolved organic carbon (DOC) and carbohydrate at 50 and 500µgL-1 treatments were significantly increased. The increase of DOC and carbohydrate in root exudates was due to rice root membrane permeability changes induced by MCs. Overall, this study indicated that MCs significantly inhibited rice root growth and affected root exudation.

Effects of light, microorganisms, farming chemicals and water content on the degradation of microcystin-LR in agricultural soils.

An experiment was conducted to investigate the effect of farming activities on microcystin-LR (MC-LR) degradation in soils. Three farming activities were assessed: 1) fertilization via addition of different nitrogen sources and organic matter; 2) pesticide application by addition of different commercial pesticides; and 3) irrigation by addition of different amount of water. The contribution of the two major degradation processes of MC-LR in soils, photodegradation and biodegradation, were also evaluated. MC-LR was added into the soil samples to create a concentration of 500 µg kg-1 for each treatment. Results showed that natural degradation of MC-LR in soils was mainly by biodegradation rather than photodegradation. MC-degradation was stimulated by the addition of NaNO3 and humic acid, whereas degradation was inhibited by addition of NH4Cl, glucose, and glycine. Application of high concentrations of glyphosate and chlorothalonil significantly inhibited the degradation of MC-LR in soils and the half-life was almost twice as long as the control. No significant effect was found by addition of CO(NH2)2 and dimethoate. Both low (10%) and high water content (60%) could lead to inhibition of MC-LR degradation. Results from our study help to inform farm practices that could alleviate contamination by MC-LR in agroecosystems.

Understanding the Cubic Phase Stabilization and Crystallization Kinetics in Mixed Cations and Halides Perovskite Single Crystals.

The spontaneous α-to-δ phase transition of the formamidinium-based (FA) lead halide perovskite hinders its large scale application in solar cells. Though this phase transition can be inhibited by alloying with methylammonium-based (MA) perovskite, the underlying mechanism is largely unexplored. In this Communication, we grow high-quality mixed cations and halides perovskite single crystals (FAPbI3)1-x(MAPbBr3)x to understand the principles for maintaining pure perovskite phase, which is essential to device optimization. We demonstrate that the best composition for a perfect α-phase perovskite without segregation is x = 0.1-0.15, and such a mixed perovskite exhibits carrier lifetime as long as 11.0 µs, which is over 20 times of that of FAPbI3 single crystal. Powder XRD, single crystal XRD and FT-IR results reveal that the incorporation of MA+ is critical for tuning the effective Goldschmidt tolerance factor toward the ideal value of 1 and lowering the Gibbs free energy via unit cell contraction and cation disorder. Moreover, we find that Br incorporation can effectively control the perovskite crystallization kinetics and reduce defect density to acquire high-quality single crystals with significant inhibition of δ-phase. These findings benefit the understanding of α-phase stabilization behavior, and have led to fabrication of perovskite solar cells with highest efficiency of 19.9% via solvent management.

Increment of root membrane permeability caused by microcystins result in more elements uptake in rice (Oryza sativa).

We conducted an indoor culture experiment to evaluate the phytotoxic effect of microcystins (MCs) on rice. After a 30day exposure, MCs induced a clear inhibition in rice growth, as well as a disruption of its antioxidant system and lipid peroxidation. We observed an increase in root membrane permeability; the conductivity of the leakage solution of the roots at 50 and 500µgL-1 was significantly increased by 77% and 136%, respectively, compared to the control. Uptake of microelements (Fe, Mn, Cu and Zn) was generally not affected after the 30day exposure to MCs. In contrast, uptake of macroelements, with the exception of K, was stimulated by MCs. Ca content in roots exposed to 500µgL-1 showed the greatest increase, by 47%, compared to the control. We propose the following mechanisms to explain our experimental results: exposure of rice roots to MCs leads to root damage and loss of membrane integrity, resulting in greater permeability and uptake of elements.

First Identification of the Toxicity of Microcystins on Pancreatic Islet Function in Humans and the Involved Potential Biomarkers.

Microcystins (MCs) produced by cyanobacteria have been recognized as a major public health threat. However, the toxicity of MCs to humans is still largely unknown. In this study, we examined the changes in pancreatic islet function in fishers exposed to ambient levels of MCs at Lake Taihu and, using a mouse model, explored the molecular mechanisms involved in toxicity. MCs content in the serum of fishers tested positive, with a range from 0.10 to 0.64 µg/L. Both lower blood insulin levels (2.26 ± 0.96 µIU/mL) and impaired fasting glucose were found in participants from the Meiliang Bay area in Lake Taihu, where MC-LR levels were substantially greater than the MC threshold established by WHO for drinking water. Animal experiments showed that glucose level increased by 27.9% in mice exposed to 5 µg/kg bw and decreased by 41.5% in mice exposed to 20 µg/kg bw. Blood insulin levels declined by 21.9% and 56.2% in mice exposed to 5 and 20 µg/kg bw MC-LR, respectively, which was consistent with the results observed in fishers. Furthermore, the diabetes gene pdx1 and several other proteins (such as Ppp3ca, Ide, Marcks, Pgk1, Suclg1, Ndufs4) involved in insulin secretion were identified for the first time in mice following MC-LR exposure; these biomarkers were considered responsible for MC-LR induced islet dysfunction. This study suggests that subchronic exposure to environmental levels of MCs may increase the risk of the occurrence of diabetes in humans.

Organic-inorganic interactions of single crystalline organolead halide perovskites studied by Raman spectroscopy.

Organolead halide perovskites exhibit superior photoelectric properties, which have given rise to the perovskite-based solar cells whose power conversion efficiency has rapidly reached above 20% in the past few years. However, perovskite-based solar cells have also encountered problems such as current-voltage hysteresis and degradation under practical working conditions. Yet investigations into the intrinsic chemical nature of the perovskite material and its role on the performance of the solar cells are relatively rare. In this work, Raman spectroscopy is employed together with CASTEP calculations to investigate the organic-inorganic interactions in CH3NH3PbI3 and CH3NH3PbBr3-xClx perovskite single crystals with comparison to those having ammonic acid as the cations. For Raman measurements of CH3NH3PbI3, a low energy line of 1030 nm is used to avoid excitation of strong photoluminescence of CH3NH3PbI3. Raman spectra covering a wide range of wavenumbers are obtained, and the restricted rotation modes of CH3-NH3(+) embedded in CH3NH3PbBr3 (325 cm(-1)) are overwhelmingly stronger over the other vibrational bands of the cations. However, the band intensity diminishes dramatically in CH3NH3PbBr3-xClx and most of the bands shift towards high frequency, indicating the interaction with the halides. The details of such an interaction are further revealed by inspecting the band shift of the restricted rotation mode as well as the C-N, NH3(+) and CH3 stretching of the CH3NH3(+) as a function of Cl composition and length of the cationic ammonic acids. The results show that the CH3NH3(+) interacts with the PbX3(-) octahedral framework via the NH3(+) end through N(+)-HX hydrogen bonding whose strength can be tuned by the composition of halides but is insensitive to the size of the organic cations. Moreover, an increase of the Cl content strengthens the hydrogen bonding and thus blueshifts the C-N stretching bands. This is due to the fact that Cl is more electronegative than Br and an increase of the Cl content decreases the lattice constant of the perovskite. The findings of the present work are valuable in understanding the role of cations and halides in the performance of MAPbX3-based perovskite solar cells.

Multidentate Fullerenes Enable Tunable and Robust Interfacial Bonding for Efficient Tin-Based Perovskite Solar Cells.

Improving the efficiency of tin-based perovskite solar cells (TPSCs) is significantly hindered by energy level mismatch and weak interactions at the interface between the tin-based perovskite and fullerene-based electron transport layers (ETLs). In this study, four well-defined multidentate fullerene molecules with 3, 4, 5, and 6 diethylmalonate groups, labeled as FM3, FM4, FM5, and FM6 are synthesized, and employed as interfacial layers in TPSCs. It is observed that increasing the number of functional groups in these fullerenes leads to shallower lowest unoccupied molecular orbital (LUMO) energy levels and enhance interfacial chemical interactions. Notably, FM5 exhibits a suitable energy level and robust interaction with the perovskite, effectively enhancing electron extraction and defect passivation. Additionally, the unique molecular structure of FM5 allows the exposed carbon cage to be tightly stacked with the upper fullerene cage after interaction with the perovskite, facilitating efficient charge transfer and protecting the perovskite from moisture and oxygen damage. As a result, the FM5-based device achieves a champion efficiency of 15.05%, significantly surpassing that of the PCBM-based (11.77%), FM3-based (13.54%), FM4-based (14.34%), and FM6-based (13.75%) devices. Moreover, the FM5-based unencapsulated device exhibits excellent stability, maintaining over 90% of its initial efficiency even after 300 h of air exposure.

Efficient and Stable Monolithic Perovskite/Silicon Tandem Solar Cells Enabled by Contact-Resistance-Tunable Indium Tin Oxide Interlayer.

The imperfect charge behavior at the interfaces of perovskite/electron-transport layer (ETL)/transparent conducting oxide (TCO) limits the further performance improvement of perovskite/silicon tandem solar cells. Herein, an indium tin oxide interlayer is deposited between ETL and TCO to address this issue. Specifically, the interlayer is prepared using an all-physical and H2O-free method, electron-beam evaporation, which can avoid any potential damage to the underlying perovskite and ETL layers. Moreover, the interlayer's composition can be readily tuned by changing the evaporator component, enabling authors to regulate the contact resistance and energy-level alignment of the ETL/TCO interface. Consequently, the resultant perovskite/silicon tandem solar cells exhibit an impressive power conversion efficiency (PCE) of 30.8% (certified 30.3%). Moreover, the device retains 98% of its initial PCE after continuous operation under ambient conditions for 1078 h, representing one of the most stable and efficient perovskite/silicon tandem solar cells.

Suppressing Halide Segregation via Pyridine-Derivative Isomers Enables Efficient 1.68 eV Bandgap Perovskite Solar Cells.

Light-induced phase segregation is one of the main issues restricting the efficiency and stability of wide-bandgap perovskite solar cells (WBG PSCs). Small organic molecules with abundant functional groups can passivate various defects, and therefore suppress the ionic migration channels for phase segregation. Herein, a series of pyridine-derivative isomers containing amino and carboxyl are applied to modify the perovskite surface. The amino, carboxyl, and N-terminal of pyridine in all of these molecules can interact with undercoordinated Pb2+ through coordination bonds and suppress halide ions migration via hydrogen bonding. Among them, the 5-amino-3-pyridine carboxyl acid (APA-3) treated devices win the champion performance, enabling an efficiency of 22.35% (certified 22.17%) using the 1.68 eV perovskite, which represents one of the highest values for WBG-PSCs. This is believed to be due to the more symmetric spatial distribution of the three functional groups of APA-3, which provides a better passivation effect independent of the molecular arrangement orientation. Therefore, the APA-3 passivated perovskite shows the slightest halide segregation, the lowest defect density, and the least nonradiative recombination. Moreover, the APA-3 passivated device retains 90% of the initial efficiency after 985 h of operation at the maximum power point, representing the robust durability of WBG-PSCs under working conditions.