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Perovskite solar cells (PSCs) with state-of-the-art efficiencies contain thermally unstable methylammonium (MA). Avoiding MA molecules usually leads to a severe decrease in the cell efficiency. In this work, a novel ion liquid (simplified as NDAPBF4) possessing a pyridine cation and BF4− anion were introduced to improve the performance of MA-free PSCs. The ion liquid NDAPBF4 can optimize the grain growth of the perovskite, leading to reduced carrier traps. In particular, NDAPBF4 served as an n-type dopant and boosted the electron transportation in the perovskite films, which further suppressed the carrier non-radiative recombination at the interface between the perovskite and the electron transporting layer. Finally, PSCs with a Cs0.05FA0.95PbI3 perovskite film as the absorber achieved a remarkable efficiency of 21.25%, which was one of the highest MA-free inverted perovskite solar cells up to date. PSCs doped with NDAPBF4 also gave excellent stability, which preserved 95% and 94% of the initial efficiency after being aged for 1000 h and 500 h under room temperature and elevated temperature at 85 °C, respectively.

Inverted perovskite solar cells (PSCs) with a C60 framework are known for their common drawback of low power conversion efficiency (PCE) of

Recently, prominent works using organic monomolecular layers (MLs) as efficient hole transport layers (ML-HTLs) in inverted perovskite solar cells (PSCs) have been reported to evidently promote device performance; however, these results were achieved individually on specific organic molecules and the power conversion efficiency (PCE) was less than 20%. Herein, to explore the feasibility of extending the strategy of organic ML-HTLs to efficient PSCs and the underlying general enhancement mechanism as well as further optimizing devices to achieve competitive performances, we report an universal ML-HTL strategy, employing MLs of widely used organic hole transport materials to construct HTLs, including small molecules and polymers that are hydrophobic/hydrophilic in nature. This strategy enabled optimal MLs to be formed on ITO substrates with full coverage; meanwhile, the optimal ML thickness resulted in maximum reduction of the charge carrier transit time. Generally, the ML-HTLs not only improve the wettability of the perovskite precursor that favors the formation of compact perovskite films, but also raise the effective work function of ITO towards better energy level alignment by the formation of interface dipoles. Consequently, a substantially improved fill factor of 81.86% and a champion PCE of 20.58% were achieved with the hydrophobic small molecule ML-HTL, which are record values ever reported for inverted PSCs based on ML-HTLs. Apart from small molecules, the use of ML-HTL based on either hydrophobic or hydrophilic polymers also showed improved performances. Furthermore, the better shrouded and more compact perovskite films on ML-HTLs increased the reproducibility of PSCs, which is beneficial for commercial applications. This work demonstrates the totality and in-depth understanding of the ML-HTL strategy and its potential for the development of highly efficient inverted PSCs.

Numerous fabrication methods have been developed for high-efficiency perovskite solar cells (PSCs). However, these are limited to spin-coating processes in a glove box and are yet to be commercialized. Therefore, there is a need to develop a controllable and scalable deposition technique that can be carried out under ambient conditions. Even though the doctor-blade coating technique has been widely used to prepare PSCs, it is yet to be applied to high-efficiency PSCs under ambient conditions (RH∼45%, RT∼25 °C). In this study, we conducted blade-coating fabrication of modified high-efficiency PSCs under such conditions. We controlled the substrate temperature to ensure phase transition of perovskite and added dimethyl sulfoxide (DMSO) to the perovskite precursor solution to delay crystallization, which can facilitate the formation of uniform perovskite films by doctor-blade coating. The as-prepared perovskite films had large crystal domains measuring up to 100 µm. Solar cells prepared from these films exhibited a current density that was enhanced from 17.22 to 19.98 mA/cm2 and an efficiency that was increased from 10.98% to 13.83%. However, the open-circuit voltage was only 0.908 V, probably due to issues with the hole-transporting layer. Subsequently, we replaced poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) with NiOx as the hole-transporting material and then prepared higher-quality perovskite films by blade-coating under ambient conditions. The as-prepared perovskite films were preferably orientated and had large crystal domains measuring up to 200 µm; The open-circuit voltage of the resulting PSCs was enhanced from 0.908 to 1.123 V, while the efficiency increased from 13.83% to 15.34%.

Summary The buccal mucosa (BM) is a critical first line of defense in terrestrial animals. To gain further insights into the evolutionary origins and primordial roles of BM in teleosts here we show that rainbow trout, a teleost fish, contains a diffuse mucosal associated lymphoid tissue (MALT) within its buccal cavity. Upon parasite infection, a fish immunoglobulin specialized in mucosal immunity (sIgT) was induced to a high degree, and parasite-specific sIgT responses were mainly detected in the buccal mucus. Moreover, we show that the trout buccal microbiota is prevalently coated with sIgT. Overall our findings revealed that the MALT is present in the BM of a non-tetrapod species. As fish IgT and mucus-producing cells are evolutionarily unrelated to mammalian IgA and salivary glands, respectively, our findings indicate that mucosal immune responses in the BM of teleost fish and tetrapods evolved through a process of convergent evolution., Graphical Abstract, Highlights • A mucosal associated lymphoid tissue is identified in teleost buccal cavity • Local immune responses can be induced in teleost buccal mucosa • Teleost IgT plays important roles in defending against buccal pathogen • Microbiota in teleost buccal mucosa is prevalently coated with secreted IgT, Biological Sciences; Immunology; Omics; Transcriptomics

Quasi-two-dimensional (Q-2D) perovskites ((RNH3)2MAn−1PbnI3n+1, RNH3 represents the organic spacer (mostly phenethylammonium (PEA) and n-butylammonium (BA)) and MA = methylammonium) have shown great potential for application in solar cells due to their intrinsic stability, where the organic spacer dominantly determines the Q-2D perovskite ambient stability and device performance. Current studies merely concentrate on unary organic spacer Q-2D perovskites, either using BA or PEA. Herein, for the first time, we have successfully designed and fabricated (PEA1−xBAx)2MA3Pb4I13 binary spacer-based Q-2D perovskite films, and demonstrated that the device using binary organic spacer-based Q-2D perovskite films has substantially better performance than that using either of the unary organic spacer-based Q-2D perovskite films. The (PEA0.8BA0.2)2MA3Pb4I13 binary spacer device yields a maximum power conversion efficiency of 15.7%, which outperforms the efficiency record (12–14%) for unary spacer (PEA or BA) Q-2D perovskite devices. In particular, a peak open-circuit voltage of 1.21 V is achieved due to a non-radiative recombination loss of ∼100 mV, the lowest reported loss value for Q-2D perovskite devices. The high device performance results from binary-spacer-induced intensified film surface quality, preferable vertical orientation of crystals and improved film optoelectronic properties as well as obviously decreased device recombination losses. These findings open up a new avenue for the rational design of Q-2D perovskite materials with polynary organic spacer.

We report on a method of precursor engineering to prepare high quality and stable perovskites based on formamidinium/methylammonium (FAMA) mixed-cations. CsI is commonly used to inhibit the photoinactive phase in FAMA perovskites. However, the hydrophilic nature of CsI would result in a structural instability issue at high relative humidity (RH). Besides, in inverted perovskite solar cells (PSCs) based on organic hole transport layers, the low conduction band minimum (CBM) of FAMA perovskites would lead to small open circuit voltage (Voc) (∼1.0 V), and thus additional surface passivation/modification layers are normally employed, indicating that it is essential to improve the basic precursors for high quality perovskite films. Herein, the proposed method is realized via ternary precursor alloying which endows the perovskite with increased grain size, enhanced crystallinity, reduced trap states, and a pure photoactive phase without the assistance of CsI. Without passivation/modification layers, the device Voc is enhanced markedly from 1.0 V to 1.1 V on average, and a champion power conversion efficiency of 20.7% with negligible hysteresis is achieved. Moreover, as they are free of hydrophilic CsI, both the photoactive perovskite films and devices exhibit excellent stability in ambient air. At high RH (70%), the optimized device without encapsulation only loses 16% of its efficiency after 1000 h storage, indicating the potential for the development of efficient and stable PSCs.

Although great efforts have been devoted to enhancing the efficiency and stability of perovskite solar cells (PSCs), the performance of PSCs has been far lower than anticipated. Interface engineering is helpful for obtaining high efficiency and stability through control of the interfacial charge transfer in PSCs. This paper demonstrates that the efficiency and stability of PSCs can be enhanced by introducing stable α-CsPbI3 quantum dots (QDs) as an interface layer between the perovskite film and the hole transport material (HTM) layer. By synergistically controlling the valence band position (VBP) of the perovskite and the interface layer, an interface engineering strategy was successfully used to increase the efficiency of hole transfer from the perovskite to the HTM layer, resulting in the power conversion efficiency increasing from 15.17 to 18.56%. In addition, the enhancement of the stability of PSCs can be attributed to coating inorganic CsPbI3 QDs onto the perovskite layer, which have a high moisture stability and result in long-term stability of the PSCs in ambient air.

Heavy-metal-free I-III-VI2 quantum dots (QDs) have recently emerged as favorable alternatives to toxic II-VI QDs for optoelectronic and biological applications, but low fluorescence efficiency is a key issue related to the promising nanocrystals. In this work, we demonstrate big enhancement of two-photon fluorescence efficiency and low threshold two-photon pumped amplification of spontaneous emission (ASE) of Zn-processed CuInS2 (CIS) QDs for the first time. The change of two-photon process caused by Zn2+ cation exchange in CIS QDs is systematically investigated. Two-photon ASE in Zn-processed CIS QDs films is achieved with a record of low threshold fluence of 5.7μJ/cm^2. With high two-photon fluorescence quantum yields and low threshold ASE, the Zn-processed CIS QDs could become a promising candidate for two-photon bio-imaging, nonlinear optical and novel QDs laser devices.

A delicate control of crystallization and morphology of perovskite absorbers is critical to obtain high performance hybrid perovskite solar cells (PSCs). Here, we have developed a novel crystallization strategy which involves hydration water induced intermediate phase formation under heat assisted spin-coating processing (HASP) to manipulate the morphology and grain size of perovskite films, and thus it can avoid the use of toxic and volatile antisolvents used in conventional one-step solution processes to make PSCs. During HASP, impressive morphological evolution of films occurs with the formation of CH3NH3PbI3·xH2O perovskite intermediate phases. With ingenious control of the crystallization kinetics, highly crystalline perovskite films with fewer defect states and high carrier lifetimes are obtained. The corresponding PSCs exhibit a power conversion efficiency (PCE) of 19.12% with a stabilized power output efficiency of 18.89% at the maximum power point, which is a 70% enhancement compared to that of conventional one-step process based PSCs. Furthermore, the PSC fabricated by the HASP method achieved a PCE of 15.47% with an active area of 1.2 cm2. Moreover, the flexible PSCs fabricated by the HASP method achieved a record efficiency of 14.87% with negligible hysteresis for PEDOT:PSS-based flexible inverted PSCs. Our work opens up a new avenue for morphology and crystallization control through hydration water induced intermediate phase formation under HASP, which paves the way toward further enhancing the device performance of perovskite solar cells.

It is highly desirable to develop flexible solid-state electrochemical double-layer capacitors (EDLCs) with non-liquid electrolyte. However, it is still a great challenge to prepare gel polymer electrolyte (GPE) possessing high ionic conductivity and good mechanical property. In this work, a simple and novel method to improve the conductivity and mechanical properties of GPE film for their applications as electrolyte and separator in EDLC is presented. The GPE film is prepared by cross-linking ionic liquid (IL) with poly (ethylene oxide) (PEO) and benzophenone (Bp) followed by ultraviolet (UV) irradiation. Then, a non-woven cellulose separator (FPC) is used to absorb the GPE. By tuning the mass ratio (n) between IL and PEO, the flexible EDLC cooperated with low-cost active carbon and the electrolyte film with n = 10 has a high capacitance of 70.84 F∙g−1, a wide and stable electrochemical window of 3.5 V, an energy density of 30.13 Wh∙kg−1 and a power density of 874.8 W∙kg−1 at a current density of 1 A∙g−1, which can drive a 3.0 V light-emitting diode (LED). Importantly, the excellent performance of the flexible and low-cost EDLC can be maintained at a bending angle up to 180°, indicating the ultra-flexibility. It is expected that the IL-PEO-FPC electrolyte film is a promising candidate of GPE for flexible devices and energy storage systems.

Eliminating the carrier recombination loss is of great significance for the performance of the perovskite solar cells. Here, three small molecules with the same core unit (ITIC) but different end groups (nominally IT-M and IT-4F) were incorporated into the perovskite films by engineering the composition of the perovskite precursor solutions. It is suggested that the molecules not only increase the grain size and passivate the non-coordinated Pb2+ cations among the grain boundaries, but also balance the carrier transport by regulating the electronic structure of the perovskite/molecule hybrid films (PMHFs), and produce a hydrophobic surface to prohibit the moisture permeation into the active layers. Finally, the devices based on PMHFs exhibits a significant improvement in photoelectric conversion efficiency (PCE) and the stability. The PSCs based on IT-4F realizes a champion PCE of 19.75% (reverse sweep up to 20.08%), which is far larger than those control ones (16.65%). Cells sustain over 90% of their initial efficiency after 20 days in a N2-filled glove box.

Hierarchical materials are a favourite for energy storage/harvesting technologies, such as supercapacitors and electrically-driven hydrogen production. In this work, we report a robust and highly active nanomaterial for pseudocapacitors and hydrogen production by growing vanadium pentoxide on the surface of nickel sulfide (denoted as V2O5@Ni3S2). V2O5@Ni3S2 shows a capacitance of up to 854 F g−1 at a current density of 1 A g−1 and good rate capability. The capacitance can retain ca. 60% of the initial specific capacitance even after 1000 cycles at a current density of 1 A g−1. For the hydrogen evolution reaction (HER), the overpotential of V2O5@Ni3S2 is around 95 mV at 10 mA cm−2. The excellent electrochemical performance of the V2O5@Ni3S2 hybrid is attributed to the synergistic effect between vanadium pentoxide and nickel sulfide for pseudocapacitors, and the V2O5@Ni3S2 interface and V–S active bonding in the hierarchical structure for the HER. This work demonstrates an effective structure design for supercapacitors with high energy density and for efficient hydrogen production with high catalytic activity by incorporating metal oxide with metal sulfide.

Methylammonium lead iodide (MAPbI3) perovskite has emerged as a dazzling nova in the solar cell realm. However, the robustness or stability of the material exposed to different ambiences is a key issue. In this paper, resonance Raman spectroscopy is combined with surface and bulk crystal characterizations to interpret the oxygen intercalation phenomenon on the surface of MAPbI3. We observe that oxygen can intercalate into the frameworks of MAPbI3 with the assistance of laser excitation. By lowering down the pressure in the experimental chamber, the intercalated oxygen can be readily removed. X-ray photoelectron spectroscopy and X-ray diffraction characterizations suggest that Pb–O bonds are mainly formed on the surface of MAPbI3 but are constrained to avoid the formation of PbO compound. The quantum chemical calculation based on density functional theory supports the above conclusions. The understanding of oxygen intercalation in MAPbI3 shall benefit the improvement of stability of the important solar cel...

In recent years, ternary organic solar cells, which enable extended spectral response range compared to their binary counterpart, have been emerging as an attractive strategy for obtaining impressive photovoltaic properties. In this work, the third component of PBDB-T with a medium bandgap was introduced into PBT7-Th: PC71BM host system to fabricate high efficiency ternary solar cells. It was revealed that PBDB-T not only broadens the light absorption range, but also provides pathway for energy transfer via a Firster resonance energy transfer (FRET) regime. Finally, a champion PCE of 9.45% is achieved for the bulk heterojunction (BHJ) ternary solar cells with 15 wt% PBDB-T, which is 11% enhancement in PCE compared with the host binary OSCs. These results indicate that broadening absorption range is an effective strategy to improve OSCs performance.

Methylammonium lead-iodide (CH3NH3PbI3, hereafter referred to as MAPbI3) perovskite has emerged as a dazzling nova in the solar cell realm. To date, the surface physics of these materials is still puzzling, but in this work, we demonstrate that the optical dynamics in MAPbI3 is primarily determined by the surface states. Pb dangling bonds on the surface of MAPbI3 introduce shallow electronic states. The carrier localization effect for these electronic states is rather weak as the lifetimes of the carriers on the iodine-poor surface are comparative to those in the interior region of MAPbI3. In contrast, rich-iodine on the surface of MAPbI3 induces deep trap centers for the carriers, which are detrimental to long carrier diffusion lengths. It is further proved that the surface passivation, which surprisingly prolongs the carrier diffusion lengths, mainly works on the rich-iodine on the surface rather than the Pb dangling bonds. This better understanding of the surface physics could provide essential information for improving the performance of photoelectronic devices based on MAPbI3 perovskites.

MXenes and doped carbon nanotubes (CNTs) have entered into research arenas for high-rate energy storage and conversion. Herein, a method of postsynthesis of MXenes in boron, nitrogen codoped CNTs (BNCNTs) is reported with their electrocatalytical hydrogen evolution performance. The encapsulation of hexagonal molybdenum nitrate nanoparticles (h-MoN NPs) into BNCNTs protects h-MoN NPs from agglomeration and poisoning in the complex environment. In principle, the synergism of B and N dopants on the doped CNTs and confined h-MoN NPs produces extremely active sites for electrochemical hydrogen evolution. Density functional theory calculations reveal that the active sites for hydrogen evolution originate from the synergistic effect of h-MoN(001)/CN (graphitic N doping) and h-MoN(001)/BNC. The h-MoN@BNCNT electrocatalyst exhibits a small overpotential of 78 mV at 10 mA cm and Tafel slope of 46 mV per decade, which are dramatically improved over all reported MoN-based materials and doped CNTs. Additionally, it also exhibits outstanding electrochemical stability in environments with various pH values and seawater media from South China Sea.