Influence of Donor Skeleton on Intramolecular Electron Transfer Amount for Efficient Perovskite Solar Cells.

The passivation of the defects derived from rapid-crystallization with electron-donating molecules is always a prerequisite to obtain desirable perovskite films for efficient and stable solar cells, thus, the in-depth understanding on the correlations between molecular structure and passivation capacity is of great importance for screening passivators. Here, we introduce the double-ended amide molecule into perovskite precursor solution to modulate crystallization process and passivate defects. By regulating the intermediate bridging skeletons with alkyl, alkenyl and benzene groups, the results show the passivation strength highly depends on the spin-state electronic structure that serves as an intrinsic descriptor to determine the intramolecular charge distribution by controlling orbital electron transfer from the donor segment to acceptor segment. Upon careful optimization, the benzene-bridged amide molecule demonstrates superior efficacy on improving perovskite film quality. As a physical proof-of-concept, the carbon-based, all-inorganic CsPbI2Br solar cell delivers a significantly increased efficiency of 15.51 % with a remarkably improved stability. Based on the same principle, a champion efficiency of 24.20 % is further obtained on the inverted (Cs0.05MA0.05FA0.9)Pb(I0.93Br0.07)3 solar cell. These findings provide new fundamental insights into the influence of spin-state modulation on effective perovskite solar cells.

Strain engineering improves the photovoltaic performance of carbon-based hole-transport-material free CsPbIBr2 perovskite solar cells.

Alkylamines with different chain lengths including n-butylamine, n-hexylamine, and n-octylamine, are applied to regulate the CsPbIBr2 perovskite film quality by strain engineering. The status of residual strains is controllably modulated, resulting in improved efficiency and stability of carbon-based hole-transport-material free CsPbIBr2 perovskite solar cells.

Healing the Buried Interface by a Plant-Derived Green Passivator for Carbon-Based CsPbIBr2 Perovskite Solar Cells.

Perovskite solar cells (PSCs) have attracted extensive attention in photovoltaic applications owing to their superior efficiency, and the buried interface plays a significant role in determining the efficiency and stability of PSCs. Herein, a plant-derived small molecule, ergothioneine (ET), is adopted to heal the defective buried interface of CsPbIBr2-based PSC to improve power conversion efficiency (PCE). Because of the strong interaction between Lewis base groups (-C═O and -C═S) in ET and uncoordinated Pb2+ in the perovskite film from the theoretical simulations and experimental results, the defect density of the CsPbIBr2 perovskite film is significantly reduced, and therefore, the nonradiative recombination in the corresponding device is simultaneously suppressed. Consequently, the target device achieves a high PCE of 11.13% with an open-circuit voltage (VOC) of 1.325 V for hole-free, carbon-based CsPbIBr2 PSCs and 14.56% with a VOC of 1.308 V for CsPbI2Br PSCs. Furthermore, because of the increased ion migration energy, the detrimental phase segregation in this mixed-halide perovskite is weakened, delivering excellent long-term stability for the unencapsulated device in ambient conditions over 70 days with a 96% retention rate of initial efficiency.

The Guidelines for the Design and Synthesis of Transition Metal Atom Doped Carbon Dots.

Atoms doping is a practical approach to modulate the physicochemical properties of carbon dots (CDs) and thus has garnered increasing attention in recent years. Compared to non-metal atoms, transition metal atoms (TMAs) possess more unoccupied orbitals and larger atomic radii. TMAs doping can significantly alter the electronic structure of CDs and bestow them with new intrinsic characteristics. TMAs-doped CDs have exhibited widespread application potential as a new class of single-atom-based nanomaterials. However, challenges remain for the successful preparation and precise design of TMAs-doped CDs. The key to successfully preparing TMA-doped CDs lies in anchoring TMAs to the carbon precursors before the reaction. Herein, taking the formation mechanism of TMAs-doped CDs as a starting point, we systematically summarized the ligands employed for synthesizing TMAs-doped CDs and proposed the synthetic strategy involving multiple ligands. Additionally, we summarize the functional properties imparted to CDs by different TMA dopants to guide the design of TMA-doped CDs with different functional characteristics. Finally, we describe the bottlenecks TMAs-doped CDs face and provide an outlook on their future development.

Interfacial dipole engineering in all-inorganic perovskite solar cells.

Severe nonradiative recombination and energy level mismatch in perovskite solar cells (PSCs) are key factors affecting efficiency. Here, we report an effective strategy for surface passivation and interfacial dipole engineering of perovskite films. By precisely introducing electron-withdrawing and electron-donating groups on 7-azaindole, we have effectively controlled the passivation ability of N atoms and the polarity of the interfacial dipole, thereby regulating the perovskite surface's work function and obtaining the optimal energy level matching. This strategy yields an impressive efficiency of 10.76% for the CsPbBr3 PSC and exceptional stability.

Self-powered PtNi-polyaniline films for converting rain energy into electricity.

Developing novel rainwater energy harvesting beyond conventional electricity is a promising strategy to address the problems of the energy crisis and environmental pollution. In this current work, a class of self-powered PtNi and optimal PtNi-polyaniline (PANI) films are successfully developed to convert rainwater into electricity for power generation. The maximized current, voltage and power of the self-powered PtNi-PANI films are 4.95 µA per droplet, 69.85 µV per droplet and 416.54 pW per droplet, respectively, which are attributed to the charging/discharging electrical signals between the cations provided by the rainwater and the electrons offered by the films. These results indicate that the optimized signal values are highly dependent on the elevated electron concentration of films, as well as the concentration, radius and charge of ions in rainwater. This work provides fresh insights into rain energy and enriches our knowledge of how to convert renewable energy into electricity generation.

Synergistic effect of alkali metal doping and thiocyanate passivation in CsPbBr3 for HTM-free all-inorganic perovskite solar cells.

All-inorganic CsPbBr3 perovskite solar cells (PSCs) without hole-transport materials (HTMs) have attracted widespread attention because of their significant environmental stability. However, the poor quality of perovskite film and the energetics mismatch between CsPbBr3 and charge-transport layers limit the further improvement of the CsPbBr3 PSC performance. To solve this issue, the synergistic effect of alkali metal doping and thiocyanate passivation in NaSCN and KSCN dopants is utilized to improve the properties of the CsPbBr3 film. The Na+ and K+ with smaller ionic radii are doped at the A-site of CsPbBr3 to cause a lattice contraction, which contributes to the formation of CsPbBr3 film with enhanced grain size and crystallinity. The SCN- exerts the function of passivating the uncoordinated Pb2+ defects of CsPbBr3 film, leading to a reduction of trap state density. The incorporation of NaSCN and KSCN dopants also adjusts the band structure of CsPbBr3 film to improve the interfacial energetics match of the device. As a result, the charge recombination is suppressed, and the charge transfer and extraction are effectively promoted, delivering a highly enhanced power conversion efficiency of 10.38% for the champion KSCN doped CsPbBr3 PSCs without HTMs compared to 6.72% efficiency for the original device. Moreover, the stability of the unencapsulated PSCs under ambient conditions with high humidity (85% RH, 25 °C) is distinctly improved, retaining 91.1% of the initial efficiency after 30 days of aging.

Liquid buried interface to slide lattice and heal defects in inorganic perovskite solar cells.

The residual tensile strain, which is induced by lattice and thermal expansion coefficient difference between upper perovskite film and underlying charge transporting layer, significantly deteriorates the power conversion efficiency (PCE) and stability of a halide perovskite solar cell (PSC). To overcome this technical bottleneck, herein, we propose a universal liquid buried interface (LBI) by introducing a low melting-point small molecule to replace traditional solid-solid interface. Arising from the movability upon solid-to-liquid phase conversion, LBI plays a role of "lubricant" to effectively free the soft perovskite lattice shrinkage or expansion rather than anchoring onto the substrate, leading to the reduced defects due to the healing of strained lattice. Finally, the inorganic CsPbIBr2 PSC and CsPbI2Br cell achieve the best PCEs of 11.13 % and 14.05 %, respectively, and the photo-stability is improved by 33.3-fold because of the suppressed halide segregation. This work provides new insights on the LBI for making high-efficiency and stable PSC platforms.

Universal Energy Solution for Triboelectric Sensors Toward the 5G Era and Internet of Things.

The launching of 5G technology provides excellent opportunity for the prosperous development of Internet of Things (IoT) devices and intelligent wireless sensor nodes. However, deploying of tremendous wireless sensor nodes network presents a great challenge to sustainable power supply and self-powered active sensing. Triboelectric nanogenerator (TENG) has shown great capability for powering wireless sensors and work as self-powered sensors since its discovery in 2012. Nevertheless, its inherent property of large internal impedance and pulsed "high-voltage and low-current" output characteristic seriously limit its direct application as stable power supply. Herein, a generic triboelectric sensor module (TSM) is developed toward managing the high output of TENG into signals that can be directly utilized by commercial electronics. Finally, an IoT-based smart switching system is realized by integrating the TSM with a typical vertical contact-separation mode TENG and microcontroller, which is able to monitor the real-time appliance status and location information. Such design of a universal energy solution for triboelectric sensors is applicable for managing and normalizing the wide output range generated from various working modes of TENGs and suitable for facile integration with IoT platform, representing a significant step toward scaling up TENG applications in future smart sensing.

Charge transfer doping of graphene oxide with nickel oxide nanoparticles for stable and efficient carbon-based, all-inorganic CsPbBr3 perovskite solar cells.

All-inorganic CsPbBr3 perovskite solar cells have received growing attention in the photovoltaic field due to their high stability, low cost, and simple preparation processes. However, the high-density defects in perovskite films and the large energy differences at interfaces have been the main challenges for achieving high power conversion efficiency and good stability. In this work, nickel oxide (NiOx) decorated graphene oxide (GO) is used as a hole collector at the perovskite/carbon interface for a carbon-based CsPbBr3 perovskite solar cell. The crystallinity of the CsPbBr3 perovskite layer and the hole extraction ability are markedly enhanced because of the p-type charge transfer doping of GO from oxygenic groups to NiOx. Finally, the all-inorganic CsPbBr3 perovskite solar cell achieves a power conversion efficiency of 8.59%. More importantly, the best solar cell free of encapsulation retains 94.2% of its initial efficiency in an air environment over 21 days.

A trifunctional polyethylene oxide buffer layer for stable and efficient all-inorganic CsPbBr3 perovskite solar cells.

Carbon-based all-inorganic perovskite solar cells have attracted growing interest owing to their simple fabrication process, low cost, and high stability in air. On account of the large interfacial energy barriers and polycrystalline features of perovskite films, the carrier interface recombination and inherent defects in the perovskite layer are still great challenges in further increasing the power conversion efficiency and stability of carbon-based PSCs. We present here a trifunctional polyethylene oxide buffer layer at the perovskite/carbon interface to promote the PCE and stability of carbon-based all-inorganic CsPbBr3 PSCs: (i) the PEO layer increases the crystallinity of inorganic CsPbBr3 grains for low defect state density; (ii) the oxygenic groups in PEO chains passivate the defects on the perovskite surface; and (iii) the long hydrophobic alkyl chains improve the stability in moisture. The best encapsulated PSC achieves a PCE of 8.84% and maintains 84.8% of its initial efficiency in air with 80% RH over 30 days.

Round-comb Fe2O3@SnO2 heterostructures enable efficient light harvesting and charge extraction for high-performance all-inorganic perovskite solar cells.

The precise design of an electron transport layer (ETL) to improve the light-harvesting and quality of perovskite (PVK) film plays a crucial role in the photovoltaic performance of n-i-p perovskite solar cells (PSCs). In this work, a novel three-dimensional (3D) round-comb Fe2O3@SnO2 heterostructure composites with high conductivity and electron mobility induced by its Type-II band alignment and matched lattice spacing is prepared and employed as an efficient mesoporous ETL for all-inorganic CsPbBr3 PSCs. Arising from the multiple light scattering sites provided by the 3D round-comb structure, the diffuse reflectance of Fe2O3@SnO2 composites is increased to improve the light absorption of the deposited PVK film. Besides, the mesoporous Fe2O3@SnO2 ETL affords not only more active surface for sufficient exposure to the CsPbBr3 precursor solution but also a wettable surface to reduce the barrier for heterogeneous nucleation, which realizes the regulated growth of a high-quality PVK film with less undesired defect. Hence, both the light-harvesting capability, the photoelectrons transport and extraction are improved, and the charge recombination is restrained, delivering an optimized power conversion efficiency (PCE) of 10.23 % with a high short-circuit current density of 7.88 mA cm-2 for the c-TiO2/Fe2O3@SnO2 ETL based all-inorganic CsPbBr3 PSCs. Moreover, under lasting erosion at 25 °C and 85 % RH for 30 days and light-soaking (AM 1.5G) for 480 h in air atmosphere, the unencapsulated-device shows superiorly persistent durability.

A photovoltaic-hydrovoltaic-coupled carbon-based, all-inorganic CsPbBr3 perovskite solar cell.

A photovoltaic-hydrovoltaic-coupled carbon-based, all-inorganic Cs0.91Rb0.09PbBr3 perovskite solar cell achieved a peak power conversion efficiency of 9.40% under one sun illumination and a maximum voltage of 0.39 V and current of 1.40 µA in a flowing vapor atmosphere.

Unraveling the Structure Transition and Peroxidase Mimic Activity of Copper Sites over Atomically Dispersed Copper-Doped Carbonized Polymer Dots.

The lack of systematic structural resolution makes it difficult to build specific transition-metal-atom-doped carbonized polymer dots (TMA-doped CPDs). Herein, the structure-activity relationship between Cu atoms and CPDs was evaluated by studying the peroxidase-like properties of Glu-Cu-CPDs prepared by using copper glutamate (Glu) with a Cu-N2 O2 initial structure. The results showed that the Cu atoms bound to Glu-Cu-CPDs in the form of Cu-N2 C2 , indicating that Cu-O bonds changed into Cu-C bonds under hydrothermal conditions. This phenomenon was also observed in other copper-doped CPDs. Moreover, the carboxyl and amino groups content decreased after copper-atom doping. Theoretical calculations revealed a dual-site catalytic mechanism for catalyzing H2 O2 . The detection of intracellular H2 O2 suggested their application prospects. Our study provides an in-depth understanding of the formation and catalytic mechanism of TMA-doped-CPDs, allowing for the generation specific TMA-doped-CPDs.

In situ formation of inorganic healing overlayer for interface-stabilized all-inorganic CsPbIBr2 perovskite solar cells.

A perovskite layer functionalized to be an outermost screen can strongly affect the capacity of the underlying device to avoid becoming decomposed under external stimuli, and subsequently affect the photovoltaic performance as well. Herein, we report an interface-stabilization strategy for an all-inorganic CsPbIBr2 film involving forming in situ an inorganic ZrO2 layer to solidify the soft perovskite lattice. As a result of defect passivation and self-encapsulation, the best device achieved an enhanced efficiency of up to 10.12%, which was much higher than the 7.47% efficiency for the reference device tested, with prolonged stability under conditions of persistent light irradiation and exposure to air.

Electronic metal-support interaction constructed for preparing sinter-resistant nano-platinum catalyst with redox property.

Generally, support materials with particular structural properties could effectively anchor metal nanoparticles and provide lower activation barriers in heterogeneous catalysis. To tailor the structure of stable iron oxide, NiFe2O4 of inverse spinel structure was obtained by combining nickel with iron element under an alkaline environment and high-temperature calcination. The p-type conductivity of NiFe2O4 provides the possibility of constructing electronic interfacial interaction with Pt nanoparticles by electron transfer. The constructed metal-support interaction could effectively stabilize Pt nanoparticles and be further enhanced during long-term harsh calcination (700 °C for 48 h) even under an O2 atmosphere. Meanwhile, the abundant structural defects of NiFe2O4 are beneficial for constructing low-temperature redox centers with the aid of Pt nanoparticles. Pt/NiFe2O4 exhibited not only excellent activity in room-temperature oxidation (CO and HCHO) and reduction reactions (chemo-selective hydrogenation of nitroarenes), but also high stability even after storage for more than 6 months. A self-adjusting mechanism triggered by structural defects is disclosed by in situ characterization and systematic reaction results. This work demonstrates an alternative concept to construct sinter-resistant and highly-effective nano-platinum catalysts robust for oxidation and reduction reactions.

Universal Dynamic Liquid Interface for Healing Perovskite Solar Cells.

Healing charge-selective contact interfaces in perovskite solar cells (PSCs) highly determines the power conversion efficiency (PCE) and stability. However, the state-of-the-art strategies are often static by one-off formation of a functional interlayer, which delivers fixed interfacial properties during the subsequent operation. As a result, defects formed in-service will gradually deteriorate the photovoltaic performances. Herein, a dynamic healing interface (DHI) is presented by incorporating a low-melting-point small molecule onto perovskite film surface for highly efficient and stable PSCs. Arising from the reduced non-radiative recombination, the DHI boosts the PCE to 12.05% for an all-inorganic CsPbIBr2 solar cell and 14.14% for a CsPbI2 Br cell, as well as 23.37% for an FA0.92 MA0.08 PbI3 (FA = formamidinium, MA = methylammonium) cell. The solid-to-liquid phase conversion of DHI at elevated temperature causes a longitudinal infiltration into the bulk perovskite film to maximize the charge extraction, passivate defects at grain boundaries, and suppress ion migration. Furthermore, the stability is remarkably enhanced under air, heat, and persistent light-irradiation conditions, paving a universal strategy for advanced perovskite-based optoelectronics.

Phase Control of Cs-Pb-Br Derivatives to Suppress 0D Cs4 PbBr6 for High-Efficiency and Stable All-Inorganic CsPbBr3 Perovskite Solar Cells.

The precise phase control of Cs-Pb-Br derivatives from 3D CsPbBr3 to 0D Cs4 PbBr6 highly determines the photovoltaic performance of all-inorganic CsPbBr3 perovskite solar cells (PSCs). Herein, the preferred phase conversion from precursor to Cs-Pb-Br derivatives is revealed by theoretically calculating the Gibbs free energies (∆G) of various phase conversion processes, allowing for a simplified multi-step solution-processable spin-coating method to hinder the formation of detrimental 0D Cs4 PbBr6 phase and enhance the photovoltaic performance of a PSC because of its large exciton binding energy, which is regarded as a recombination center. By further accelerating the interfacial charge extraction with a novel 2D transition metal dichalcogenide ReSe2 , the hole-free CsPbBr3 PSC achieves a champion efficiency of 10.67% with an impressive open-circuit voltage of 1.622 V and an excellent long-term stability. This work provides an in-depth understanding on the precise Cs-Pb-Br perovskite phase control and the effect of derivatives on photovoltaic performance of advanced CsPbBr3 PSCs.

Thermal-Triggered Dynamic Disulfide Bond Self-Heals Inorganic Perovskite Solar Cells.

One great challenge for perovskite solar cells (PSCs) lies in their poor operational stability under harsh stimuli by humidity, heat, light, etc. Herein, a thermal-triggered self-healing polyurethane (PU) is tailored to simultaneously improve the efficiency and stability of inorganic CsPbIBr2 PSCs. The dynamic covalent disulfide bonds between adjacent molecule chains in PU at high temperatures self-heal the in-service formed defects within the CsPbIBr2 perovskite film. Finally, the best device free of encapsulation achieves a champion efficiency up to 10.61 % and an excellent long-term stability in an air atmosphere over 80 days and persistent heat attack (85 °C) over 35 days. Moreover, the photovoltaic performances are recovered by a simple heat treatment.

Tailored Lattice "Tape" to Confine Tensile Interface for 11.08%-Efficiency All-Inorganic CsPbBr3 Perovskite Solar Cell with an Ultrahigh Voltage of 1.702 V.

The crystal distortion such as lattice strain and defect located at the surfaces and grain boundaries induced by soft perovskite lattice highly determines the charge extraction-transfer dynamics and recombination to cause an inferior efficiency of perovskite solar cells (PSCs). Herein, the authors propose a strategy to significantly reduce the superficial lattice tensile strain by means of incorporating an inorganic 2D Cl-terminated Ti3 C2 (Ti3 C2 Clx ) MXene into the bulk and surface of CsPbBr3 film. Arising from the strong interaction between Cl atoms in Ti3 C2 Clx and the under-coordinated Pb2+ in CsPbBr3 lattice, the expanded perovskite lattice is compressed and confined to act as a lattice "tape", in which the PbCl bond plays a role of "glue" and the 2D Ti3 C2 immobilizes the lattice. Finally, the defective surface is healed and a champion efficiency as high as 11.08% with an ultrahigh open-circuit voltage up to 1.702 V is achieved on the best all-inorganic CsPbBr3 PSC, which is so far the highest efficiency record for this kind of PSCs. Furthermore, the unencapsulated device demonstrates nearly unchanged performance under 80% relative humidity over 100 days and 85 °C over 30 days.