Bifunctional interfacial engineering enabled efficient and stable carbon-based CsPbIBr2 perovskite solar cells.

Carbon-based inorganic CsPbIBr2 perovskite solar cells (C-IPSC) have attracted widespread attention due to their low cost and excellent thermal stability. Unfortunately, due to the soft ion crystal nature of perovskite, inherent bulk defects and energy level mismatch at the CsPbIBr2/carbon interface limit the performance of the device. In this study, we introduced aromatic benzyltrimethylammonium chloride (BTACl) as a passivation layer to passivate the surface and grain boundaries of the CsPbIBr2 film. Due to the reduction of perovskite defects and better energy level arrangement, carrier recombination is effectively suppressed and hole extraction is improved. The champion device achieves a maximum power conversion efficiency (PCE) of 11.30% with reduces hysteresis and open circuit voltage loss. In addition, unencapsulated equipment exhibits excellent stability in ambient air.

Unveil the origin of voltage oscillation for sodium-ion batteries operating at -40 °C.

Voltage oscillation at subzero in sodium-ion batteries (SIBs) has been a common but overlooked scenario, almost yet to be understood. For example, the phenomenon seriously deteriorates the performance of Na3V2(PO4)3 (NVP) cathode in PC (propylene carbonate)/EC (ethylene carbonate)-based electrolyte at -20 °C. Here, the correlation between voltage oscillation, structural evolution, and electrolytes has been revealed based on theoretical calculations, in-/ex-situ techniques, and cross-experiments. It is found that the local phase transition of the Na3V2(PO4)3 (NVP) cathode in PC/EC-based electrolyte at -20 °C should be responsible for the oscillatory phenomenon. Furthermore, the low exchange current density originating from the high desolvation energy barrier in NVP-PC/EC system also aggravates the local phase transformation, resulting in severe voltage oscillation. By introducing the diglyme solvent with lower Na-solvent binding energy, the voltage oscillation of the NVP can be eliminated effectively at subzero. As a result, the high capacity retentions of 98.3% at -20 °C and 75.3% at -40 °C are achieved. The finding provides insight into the abnormal SIBs degradation and brings the voltage oscillation behavior of rechargeable batteries into the limelight.

A Catalyst-Like System Enables Efficient Perovskite Solar Cells.

High-quality perovskite films are essential for achieving high performance of optoelectronic devices; However, solution-processed perovskite films are known to suffer from compositional and structural inhomogeneity due to lack of systematic control over the kinetics during the formation. Here, the microscopic homogeneity of perovskite films is successfully enhanced by modulating the conversion reaction kinetics using a catalyst-like system generated by a foaming agent. The chemical and structural evolution during this catalytic conversion is revealed by a multimodal synchrotron toolkit with spatial resolutions spanning many length scales. Combining these insights with computational investigations, a cyclic conversion pathway model is developed that yields exceptional perovskite homogeneity due to enhanced conversion, having a power conversion efficiency of 24.51% for photovoltaic devices. This work establishes a systematic link between processing of precursor and homogeneity of the perovskite films.

Small-Molecule Copper Chloride Modulating the Buried Interfaces of Perovskite Solar Cells.

In perovskite solar cells (PSCs), tin dioxide (SnO2) is a highly effective electron transport material. On the other hand, the low intrinsic conductivity of SnO2, the high trap-state density on the surface and bulk of SnO2, and inadequate interface contacts between SnO2 and perovskite significantly impact device performance. Herein, small-molecule copper(II) chloride (CuCl2) is introduced into the SnO2 dispersion, which inhibits the agglomeration of SnO2 colloids and improves the quality of the electron transport layer. Furthermore, the introduction of CuCl2 optimizes the energy-level array between the ETL and perovskite layer (PVK) and passivates the anion/cation defects in SnO2, perovskite, and their interface, realizing the systematic modulation of the photoelectronic properties of the ETLs and PVKs as well as the PVK/ETL. As a result, the CuCl2-opmized PSC exhibits an impressive power conversion efficiency of 23.71%, along with improved stability.

Carbon-reinforced Ni3S2/Ti3C2Tx MXene composite as an anode for superior-performance lithium-ion capacitors.

Lithium ion capacitors (LICs) are a new generation of energy storage devices that combine the super energy storage capability of lithium ion batteries with the satisfactory power density of supercapacitors. The development of high-performance LICs still faces great challenges due to the unbalanced reaction kinetics at the anode and cathode. Therefore, it is an inevitable need to enhance the electron/ion transfer capability of the anode materials. In this paper, to obtain a superior-rate and high-capacity Ni3S2-based anode, highly conductive Ti3C2Tx MXene sheets were introduced to sever as the carrier of Ni3S2 nanoparticles and simultaneously an amorphous carbon layer which coats onto the surface of Ni3S2 nanoparticles was in-situ generated by the carbonization of dopamine reactant. The as-synthesized Ni3S2/Ti3C2Tx/C composite exhibits a high specific surface area (112.6 m2/g) because of the addition of Ti3C2Tx that can reduce the aggregation of Ni3S2 nanoparticles and the in-situ generated amorphous carbon layer that can suppress the growth of Ni3S2 nanoparticles. The Ni3S2/Ti3C2Tx/C anode possesses a remarkable reversible discharge specific capacity (626.0 mAh/g under 0.2 A/g current density), which increases to 1150.8 mAh/g after 400-cycle charge/discharge measurement at the same measurement condition indicating eminent cyclability, along with superior rate capability. To construct a superior-performance LIC device, a sterculiae lychnophorae derived porous carbon (SLPC) cathode with an average discharge specific capacity of 73.4 mAh/g@0.1A/g was prepared. The Ni3S2/Ti3C2Tx/C//SLPC LIC device with optimal cathode/anode mass ratio has a satisfactory energy density ranging from 32.8 to 119.1 Wh kg-1 at the corresponding power density of 8799.4 to 157.5 W kg-1, together with a prominent capacity retention (95.5 %@1 A/g after 10,000 cycles).

Novel Strategy for High Efficient and Stable Perovskite Solar Cells through Atomic Layer Deposition.

The perovskite material has demonstrated conceivable potential as an absorbing material of solar cells. Although the power conversion efficiency of the device based on perovskite has rapidly come to 26%, there are still many factors that affect the further improvement of the photoelectric conversion efficiency. Interface defects are the dominating concern that influence carrier transportation and stability. Here, we report a novel strategy where B2O3 is deposited on the fresh perovskite film by atomic layer deposition technology. The organic atmosphere during atomic layer deposition can effectively regulate the crystallization kinetics of perovskites and promote crystal growth. The B2O3 adsorbed on the perovskite light-absorption layer can effectively reduce the electropositive defects on the surface of the perovskite, such as uncoordinated Pb2+ and I vacancies due to the electron-donating properties of the side O atoms in B2O3. Consequently, the power conversion efficiency of the perovskite solar cell after B2O3 treatment increases to 21.78% from 18.89%. Simultaneously, B2O3 can improve the stability of devices.

Poly(3-hexylthiophene)/perovskite Heterointerface by Spinodal Decomposition Enabling Efficient and Stable Perovskite Solar Cells.

The best research-cell efficiency of perovskite solar cells (PSCs) is comparable with that of mature silicon solar cells (SSCs); However, the industrial development of PSCs lags far behind SSCs. PSC is a multiphase and multicomponent system, whose consequent interfacial energy loss and carrier loss seriously affect the performance and stability of devices. Here, by using spinodal decomposition, a spontaneous solid phase segregation process, in situ introduces a poly(3-hexylthiophene)/perovskite (P3HT/PVK) heterointerface with interpenetrating structure in PSCs. The P3HT/PVK heterointerface tunes the energy alignment, thereby reducing the energy loss at the interface; The P3HT/PVK interpenetrating structure bridges a transport channel, thus decreasing the carrier loss at the interface. The simultaneous mitigation of energy and carrier losses by P3HT/PVK heterointerface enables n-i-p geometry device a power conversion efficiency of 24.53% (certified 23.94%) and excellent stability. These findings demonstrate an ingenious strategy to optimize the performance of PSCs by heterointerface via Spinodal decomposition.

Multifunctional Imidazolidinyl Urea Additive Initiated Complex with PbI2 Toward Efficient and Stable Perovskite Solar Cells.

High-quality perovskite absorption layer is the fundamental basis for efficient and stable perovskite solar cells (PSCs). Due to the ionic nature of perovskite components, plentiful charged defects and suspension bonds remain on the surface of perovskite grains after continuous high-temperature annealing. Here, the complex initiated by the introduction of a multifunctional imidazolidinyl urea (IU) additive into the PbI2 precursor solution could serve as nucleation sites and crystallization templates for perovskite crystals to optimize the growth of high-quality perovskite films. By anchoring at the grain boundaries of perovskite films, IU molecules could passivate various types of defects, improve the hydrophobic properties, and inhibit lead leakage. Attributed to reduced defect density, improved charge transport, and inhibited α-FAPbI3 transition, the PSCs prepared based on IU additives achieved a champion power conversion efficiency of 23.18% (21.51% for the control PSCs) with negligible hysteresis and satisfactory stability.

Potassium-Based Dual-Ion Batteries Operating at -60 °C Enabled By Co-Intercalation Anode Chemistry.

Battery performance at subzero is restricted by sluggish interfacial kinetics. To resolve this issue, potassium-based dual-ion batteries (K-DIBs) based on the polytriphenylamine (PTPAn) cathode with anion storage chemistry and the hydrogen titanate (HTO) anode with K+ /solvent co-intercalation mechanism are constructed. Both the PTPAn cathode and the HTO anode do not undergo the desolvation process, which can effectively accelerate the interfacial kinetics at subzero. As revealed by theoretical calculations and experimental analysis, the strong K+ /solvent binding energy in the dilute electrolyte, the charge shielding effect of the crystal water, and the uniform SEI layer with high content of the flexible organic species synergically promote HTO to undergo K+ /solvent co-intercalation behavior. The special co-intercalation mechanism and anion storage chemistry enable HTO||PTPAn K-DIBs with superior rate performance and cycle durability, maintaining a capacity retention of 94.1% after 6000 cycles at -40 °C and 91% after 1000 cycles at -60 °C. These results provide a step forward for achieving high-performance energy storage devices at low temperatures.

Synergistic Effect of 2-(Trifluoromethyl) Benzimidazole on the Stability and Performance of Perovskite Solar Cells.

The quality of the perovskite active layer directly impacts the photovoltaic performance of perovskite solar cells (PSCs). Unfortunately, perovskite films produced through solution methods often have a significant number of defects on their surface, which lead to a substantial degradation in the performance of devices. For this reason, a multifunctional additive 2-(trifluoromethyl) benzimidazole (TFMBI) is introduced into perovskite films. Based on the Lewis acid/base coordination principle, the TFMBI double site cooperatively passivates surface defects, inhibiting carrier non-radiative recombination. Simultaneously, the hydrophobic solid group (-CF3) of TFMBI covers the surface, establishing a moisture-oxygen barrier and improving the environmental stability of the devices. In consequence, the power conversion efficiency (PCE) of TFMBI-modified PSCs reached 23.16%, significantly higher than the pristine one with a PCE of 20.62%. Additionally, the unencapsulated target device retained 90.32% of its initial PCE even after being reserved in the air with a relative humidity of 20-30% for 60 days.

Amorphous Co-Mo-S nanospheres fabricated via room-temperature vulcanization for asymmetric supercapacitors.

Ternary metal sulfides employed in supercapacitors exhibit better electrochemical performances than their counterpart oxides due to their superior conductivity. However, the insertion/extraction of electrolyte ions can lead to a significant volume change in electrode materials, which can result in poor cycling stability. Herein, novel amorphous Co-Mo-S nanospheres were fabricated through a facile room-temperature vulcanization method. It involves the conversion of crystalline CoMoO4 by reacting it with Na2S at room temperature. In addition to the conversion of the crystalline state into an amorphous structure with more grain boundaries, which is beneficial for the transport of electron/ion and can accommodate the volume change generated by the insertion/extraction of electrolyte ions, the production of more pores led to an increased specific surface area. The electrochemical results indicate that the as-prepared amorphous Co-Mo-S nanospheres had a specific capacitance of up to 2049.7F/g@1 A/g together with good rate capability. The amorphous Co-Mo-S nanospheres can be used as the cathode of supercapacitors and assembled with an activated carbon anode into an asymmetric supercapacitor possessing a satisfactory energy density of 47.6 Wh kg-1@1012.9 W kg-1. One of the prominent features exhibited by this asymmetric device is its remarkable cyclic stability, with a capacitance retention of 107% after 10,000 cycles.

Localized Ligands Assist Ultrafast Multivalent-Cation Intercalation Pseudocapacitance.

Rechargeable batteries based on multivalent cation (Mvn+ , n>1) carriers are considered potentially low-cost alternatives to lithium-ion batteries. However, the high charge-density Mvn+ carriers generally lead to sluggish kinetics and poor structural stability in cathode materials. Herein, we report an Mvn+ storage via intercalation pseudocapacitance mechanism in a 2D bivalve-like organic framework featured with localized ligands. By switching from conventional intercalation to localized ligand-assisted-intercalation pseudocapacitance, the organic cathode exhibits unprecedented fast kinetics with little structural change upon intercalation. It thus enables an excellent power density of 57 kW kg-1 over 20000 cycles for Ca2+ storage and a power density of 14 kW kg-1 with a long cycling life over 45000 cycles for Zn2+ storage. This work may provide a largely unexploited route toward constructing a local dynamic coordination microstructure for ultrafast Mvn+ storage.

Synergistic Ionic Liquid in Hole Transport Layers for Highly Stable and Efficient Perovskite Solar Cells.

Perovskite solar cells (PSCs) with n-i-p structures often utilize an organic 2,2',7,7'-tetrakis (N, N-di-p-methoxyphenyl-amine) 9,9'-spirobifluorene (spiro-OMeTAD) along with additives of lithium bis(trifluoromethanesulfonyl)imide salt (LiTFSI) and tert-butylpyridine as the hole transporting layer (HTL). However, the HTL lacks stability in ambient air, and numerous defects are often present on the perovskite surface, which is not conducive to a stable and efficient PSC. Therefore, constructive strategies that simultaneously stabilize spiro-OMeTAD and passivate the perovskite surface are required. In this work, it is demonstrated that a novel ionic liquid of dimethylammonium bis(trifluoromethanesulfonyl)imide (DMATFSI) could act as a bifunctional HTL modulator in n-i-p PSCs. The addition of DMATFSI into spiro-OMeTAD can effectively stabilize the oxidized spiro-OMeTAD+ cation radicals through the formation of spiro-OMeTAD+ TFSI- because of the excellent charge delocalization of the conjugated CF3 SO2 - moiety within TFSI- . In addition, DMA+ cations could move toward the perovskite from the HTL, resulting in the passivation of defects at the perovskite surface. Accordingly, a power conversion efficiency of 23.22% is achieved for PSCs with DMATFSI and LiTFSI co-doped spiro-OMeTAD. Moreover, benefiting from the improved ion migration barrier and hydrophobicity of the HTL, still retained nearly 80% of their initial power conversion efficiency after 36 days of exposure to ambient air.

High-Efficiency Carbon-based CsPbI2 Br Perovskite Solar Cells from Dual Direction Thermal Diffusion Treatment with Cadmium Halides.

In recent years, carbon-based CsPbI2 Br perovskite solar cells (PSCs) have attracted more attention due to their low cost and good stability. However, the power conversion efficiency (PCE) of carbon-based CsPbI2 Br PSCs is still no more than 16%, because of the defects in CsPbI2 Br or at the interface with the electron transport layer (ETL), as well as the energy level mismatch, which lead to the loss of energy, thus limiting PCE values. Herein, a series of cadmium halides are introduced, including CdCl2 , CdBr2 and CdI2 for dual direction thermal diffusion treatment. Some Cd2+ ions thermally diffuse downward to passivate the defects inside or on the surface of SnO2 ETL. Meanwhile, the energy level structure of SnO2 ETL is adjusted, which is in favor of the transfer of electron carriers and blocking holes. On the other hand, part of Cd2+ and Cl- ions thermally diffuse upward into the CsPbI2 Br lattice to passivate crystal defects. Through dual direction thermal diffusion treatment by CdCl2 , CdI2 and CdBr2 , the performance of devices has been significantly improved, and their PCE has been increased from 13.01% of the original device to 14.47%, 14.31%, and 13.46%, respectively. According to existing reports, 14.47% is one of the highest PCE of carbon-based CsPbI2 Br PSCs with SnO2 ETLs.

Holistically Optimizing Charge Carrier Dynamics Enables High-Performance Dye-Sensitized Solar Cells and Photodetectors.

Charge carrier events across organic electronics are ubiquitous, and the derived optimization plays a crucial effect on improving the performance of organic electronics. Herein, a two-dimensional material (Ti3C2Tx) is incorporated into titanium dioxide (TiO2) to impart the Ti3C2Tx/TiO2 hybrid film enriched hydroxy group distribution, defect-negligible surface, upshifted work function, and enhanced conductivity yet electron mobility versus the pristine TiO2 film. Therefore, intensified photon-harvesting ability, reduced charge carrier recombination, and efficient charge carrier collection are realized for dye-sensitized solar cells (DSSCs) based on the Ti3C2Tx/TiO2 hybrid photoanode relative to control ones. Consequently, the modified DSSCs based on Z907 deliver superior efficiencies of 10.39 and 29.68% under 100 mW/cm2 illumination and ∼1.9 mW/cm2 dim light, respectively, being the highest values of Z907-based DSSCs. However, control devices only obtain lower efficiencies of 8.06 and 23.91% when undergoing the abovementioned illumination. On the other hand, the self-powered homologous photodetectors with the hybrid film as an electron-transporting layer present enhanced detectivity (1.69 × 1011 Jones) and a shortened responsivity of 0.26 s versus that of control ones (1.39 × 1011 Jones and 0.35 s). Our work implies that the Ti3C2Tx/TiO2 hybrid film features high potential for improving the performance of organic electronics for its effect of holistically optimizing charge carrier dynamics.

Polarized Molecule 4-(Aminomethyl) Benzonitrile Hydrochloride for Efficient and Stable Perovskite Solar Cells.

The rapid development of perovskite solar cells (PSCs) makes it one of the most competitive photovoltaic devices in the field of new energy. However, the suboptimal performance and poor stability caused by numerous defects are still the main factors limiting the development of PSCs. Herein, a polarized molecule additive of 4-(aminomethyl) benzonitrile hydrochloride (AMBNCl) is introduced into perovskite. Owing to its special polar electron density distribution, -C≡N group, -NH3+ terminal, and Cl- ions, the modification of AMBNCl can improve the quality of perovskite crystal growth, passivate the defects of Pb2+, adjust the energy level array between the perovskite layer and hole-transport layer, and alleviate the carrier nonradiative recombination. As a result, the AMBNCl-modified device achieves a champion efficiency of 23.52%. The unpacked device still maintained 91.2% of its original efficiency after storing in an air environment (RH ∼40%, 25 °C) for 50 days.

Free-standing 3D core-shell architecture of Ni3S2@NiCoP as an efficient cathode material for hybrid supercapacitors.

The design and discovery of free-standing hybrid electrode materials with large absolute capacity and high cycling stability for energy storage become desirable and are still challenging. In this work, we demonstrate that the hybrid supercapacitor (HSC) device is assembled by 3D core-shell hierarchical nanorod arrays of Ni3S2@NiCoP nanocomposite for the first time. The Ni3S2@NiCoP nanocomposite is successfully synthesized through a facile stratagem containing hydrothermal process and the subsequent electrodeposition method. The 3D architecture of Ni3S2@NiCoP hybrid electrode composed of vertically aligned "hyperchannel" 1D Ni3S2 nanorods and highly conductive interconnected 2D nanosheets of NiCoP is beneficial to fast electron transfer kinetics, thus leading to enhancing the ionic and electronic conductivity, kinetics of redox reaction, and synergistic behavior of active species. The fabricated HSC device with Ni3S2@NiCoP electrode delivers outstanding areal capacity of 109 µAh cm-2 at a current density of 1 mA cm-2, brilliant energy density of 74.9 Wh kg-1 at a power density of 700 W kg-1, and prominent cyclic performance of 92% capacity retention even after 144-h floating test. This work demonstrates that the core-shell hierarchical nanorod arrays of Ni3S2@NiCoP can be viewed as one of the novel battery-type electrode materials for high-performance HSCs.

Single-crystalline TiO2 nanoparticles for stable and efficient perovskite modules.

Despite the remarkable progress in power conversion efficiency of perovskite solar cells, going from individual small-size devices into large-area modules while preserving their commercial competitiveness compared with other thin-film solar cells remains a challenge. Major obstacles include reduction of both the resistive losses and intrinsic defects in the electron transport layers and the reliable fabrication of high-quality large-area perovskite films. Here we report a facile solvothermal method to synthesize single-crystalline TiO2 rhombohedral nanoparticles with exposed (001) facets. Owing to their low lattice mismatch and high affinity with the perovskite absorber, their high electron mobility and their lower density of defects, single-crystalline TiO2 nanoparticle-based small-size devices achieve an efficiency of 24.05% and a fill factor of 84.7%. The devices maintain about 90% of their initial performance after continuous operation for 1,400 h. We have fabricated large-area modules and obtained a certified efficiency of 22.72% with an active area of nearly 24 cm2, which represents the highest-efficiency modules with the lowest loss in efficiency when scaling up.

Deciphering the Reduced Loss in High Fill Factor Inverted Perovskite Solar Cells with Methoxy-Substituted Poly(Triarylamine) as the Hole Selective Contact.

A dopant-free polymeric hole selective contact (HSC) layer is ubiquitous for stable perovskite solar cells (PSCs). However, the intrinsic nonwetting nature of the polymeric HSC impedes the uniform spreading of the perovskite precursor solution, generating a terrible buried interface. Here, we dexterously tackle this dilemma from the perspective of dispersive and polar component surface energies of the HSC layer. A novel triarylamine-based HSC material, poly[bis(4-phenyl)(2,4-dimethoxyphenyl)amine] (2MeO-PTAA), was designed by introducing the polar methoxy groups to the para and ortho positions of the dangling benzene. These nonsymmetrically substituted electron-donating methoxy groups enhanced the polar components of surface energy, allowing more tight interfacial contact between the HSC layer and perovskite and facilitating hole extraction. When utilized as the dopant-free HSC layer in inverted PSCs, the 2MeO-PTAA-based device with CH3NH3PbI3 as the absorber exhibited an encouraging power conversion efficiency of 20.23% and a high fill factor of 84.31% with negligible hysteresis. Finally, a revised detailed balance model was used to verify the drastically lessened surface defect-induced recombination loss and shunt resistance loss in 2MeO-PTAA-based devices. This work demonstrates a facile and efficient way to modulate the buried interface and shed light on the direction to further improve the photovoltaic performance of inverted PSCs with other types of perovskites.

High-efficiency and ultraviolet stable carbon-based CsPbIBr2 solar cells from single crystal three-dimensional anatase titanium dioxide nanoarrays with ultraviolet light shielding function.

TiO2 is commonly used to prepare electron transport layers (ETLs) in perovskite solar cells (PSCs). However, conventional TiO2 ETLs suffer from low electron mobility and charge recombination. Here, we report the direct growth of TiO2 ETLs on fluorine doped conductive (FTO) glasses with titanium tetrafluoride (TiF4) as the reactant by hydrothermal method. The TiO2 ETLs have pure anatase phase, single crystal structure and three-dimensional (3D) nanoarrays morphology. This 3D-TiO2 ETLs mainly consist of thermodynamically stable surfaces {101} and more reactive surfaces {001}. Compared with the conventional TiO2 ETLs, the 3D-TiO2 ETLs can effectively optimize energy level matching and charge transfer dynamics. The special morphology of 3D-TiO2 ETLs can well assist to form high quality CsPbIBr2 with larger crystal grains. The champion CsPbIBr2 PSC with 3D-TiO2 ETL achieves an efficiency as high as 10.65%, which is equal to the one with hole-transport and Au electrode structure (10.79%) and much higher than the pristine one (7.16%) with the conventional TiO2 ETL. Furthermore, the 3D-TiO2 ETLs show ultraviolet (UV) shielding function, which can effectively overcome the UV instability defect of conventional TiO2 ETLs and obviously enhance UV stability of CsPbIBr2 and the corresponding PSCs. Therefore, the 3D-TiO2 ETLs can be good candidates for preparing high-efficiency and UV stable carbon-based CsPbIBr2 PSCs.