Ligand Homogenized Br-I Wide-Bandgap Perovskites for Efficient NiOx-Based Inverted Semitransparent and Tandem Solar Cells.

Phase heterogeneity of bromine-iodine (Br-I) mixed wide-bandgap (WBG) perovskites has detrimental effects on solar cell performance and stability. Here, we report a heterointerface anchoring strategy to homogenize the Br-I distribution and mitigate the segregation of Br-rich WBG-perovskite phases. We find that methoxy-substituted phenyl ethylammonium (x-MeOPEA+) ligands not only contribute to the crystal growth with vertical orientation but also promote halide homogenization and defect passivation near the buried perovskite/hole transport layer (HTL) interface as well as reduce trap-mediated recombination. Based on improvements in WBG-perovskite homogeneity and heterointerface contacts, NiOx-based opaque WBG-perovskite solar cells (WBG-PSCs) achieved impressive open-circuit voltage (Voc) and fill factor (FF) values of 1.22 V and 83%, respectively. Moreover, semitransparent WBG-PSCs exhibit a PCE of 18.5% (15.4% for the IZO front side) and a high FF of 80.7% (79.4% for the IZO front side) for a designated illumination area (da) of 0.12 cm2. Such a strategy further enables 24.3%-efficient two-terminal perovskite/silicon (double-polished) tandem solar cells (da of 1.159 cm2) with a high Voc of over 1.90 V. The tandem devices also show high operational stability over 1000 h during T90 lifetime measurements.

Slow-Release Effect Assisted Crystallization for Sequential Deposition Realizes Efficient Inverted Perovskite Solar Cells.

The two-step sequential deposition strategy has been widely recognized in promoting the research and application of perovskite solar cells, but the rapid reaction of organic salts with lead iodide inevitably affects the growth of perovskite crystals, accompanied by the generation of more defects. In this study, the regulation of crystal growth was achieved in a two-step deposition method by mixing 1-naphthylmethylammonium bromide (NMABr) with organic salts. The results show that the addition of NMABr effectively delays the aggregation and crystallization behavior of organic salts; thereby, the growth of the optimal crystal (001) orientation of perovskite is promoted. Based on this phenomenon of delaying the crystallization process of perovskite, the "slow-release effect assisted crystallization" is defined. Moreover, the incorporation of the Br element expands the band gap of perovskite and mitigates material defects as nonradiative recombination centers. Consequently, the power conversion efficiency (PCE) of the enhanced perovskite solar cells (PSCs) reaches 20.20%. It is noteworthy that the hydrophobic nature of the naphthalene moiety in NMABr can enhance the humidity resistance of PSCs, and the perovskite phase does not decompose for more than 3000 h (30-40% RH), enabling it to retain 90% of its initial efficiency even after exposure to a nitrogen environment for 1200 h.

Crystallization Kinetics of Perovskite Films by a Green Mixture Antisolvent for Efficient NiOx-Based Inverted Solar Cells.

Environment-friendly antisolvents are critical for obtaining highly efficient, reproducible, and sustainable perovskite solar cells (PSCs). Here, we introduced a green mixture antisolvent of ethyl acetate-isopropanol (EA/IPA) to finely regulate the crystal grain growth and related film properties, including the morphology, crystal structure, and chemical composition of the perovskite thin film. The IPA with suitable content in EA plays a key role in achieving a smooth and compact high-quality perovskite thin film, leading to the suppression of film defect-induced nonradiative recombination. As a result, the PSCs based on the EA/IPA (5:1) antisolvent showed a power conversion efficiency of 22.9% with an open-circuit voltage of 1.17 V.

Investigation of the driving voltage on the high performance flexible ATF-ECDs based on PET/ITO/NiOX/LiTaO3/WO3/ITO.

High performance flexible all-thin-film electrochromic devices (ATF-ECDs) have been fabricated and systematically investigated by operating with different driving voltages during the electrochromic processes. The device structure (cross-section) and material properties of some main functional layers were presented and analysed. The electrochromic properties including kinetic and spectral tests were systematically investigated through combining chronoamperometry, cyclic voltammetry measurements and optical measurements. In addition, the open circuit memory measurement was also carried out. A much higher driving voltage might lead to a current leakage inside the device during coloring process. A proper driving voltage is needed for achieving high device performances. More details were widely described and deeply discussed.

Operando monitoring of dendrite formation in lithium metal batteries via ultrasensitive tilted fiber Bragg grating sensors.

Lithium (Li) dendrite growth significantly deteriorates the performance and shortens the operation life of lithium metal batteries. Capturing the intricate dynamics of surface localized and rapid mass transport at the electrolyte-electrode interface of lithium metal is essential for the understanding of the dendrite growth process, and the evaluation of the solutions mitigating the dendrite growth issue. Here we demonstrate an approach based on an ultrasensitive tilted fiber Bragg grating (TFBG) sensor which is inserted close to the electrode surface in a working lithium metal battery, without disturbing its operation. Thanks to the superfine optical resonances of the TFBG, in situ and rapid monitoring of mass transport kinetics and lithium dendrite growth at the nanoscale interface of lithium anodes have been achieved. Reliable correlations between the performance of different natural/artificial solid electrolyte interphases (SEIs) and the time-resolved optical responses have been observed and quantified, enabling us to link the nanoscale ion and SEI behavior with the macroscopic battery performance. This new operando tool will provide additional capabilities for parametrization of the batteries' electrochemistry and help identify the optimal interphases of lithium metal batteries to enhance battery performance and its safety.

Over 10% Efficient Sb2 (S,Se)3 Solar Cells Enabled by CsI-Doping Strategy.

Antimony selenosulfide (Sb2 (S,Se)3 ) is an emerging quasi-1D photovoltaic semiconductor with exceptional photoelectric properties. The low-symmetry chain structure contains complex defects and makes it difficult to improve electrical properties via doping method. This article reports a doping strategy to enhance the efficiency of Sb2 (S,Se)3 solar cells by using alkali halide (CsI) as the hydrothermal reaction precursor. It is found that the Cs and I ions are effectively doped and atomically coordinate with Sb ions and S/Se ions. The CsI-doping Sb2 (S,Se)3 absorbers exhibit enhanced grain morphologies and reduced trap densities. The consequential CsI-doping Sb2 (S,Se)3 based solar cells demonstrate favorable band alignment, suppressed carrier recombination, and improved device performance. An efficiency as high as 10.05% under standard AM1.5 illumination irradiance is achieved. This precursor-based alkali halide doping strategy provides a useful guidance for high-efficiency antimony selenosulfide solar cells.

Efficient and Stable Perovskite Solar Modules Enabled by Inhibited Escape of Volatile Species.

The intrinsically weak bonding structure in halide perovskite materials makes components in the thin films volatile, leading to the decomposition of halide perovskite materials. The reactions within the perovskite film are reversible provided that components do not escape the thin films. Here, a holistic approach is reported to improve the efficiency and stability of PSMs by preventing the effusion of volatile components. Specifically, a method for in situ generation of channel barrier layers for perovskite photovoltaic modules is developed. The resulting PSMs attain a certified aperture PCE of 21.37%, and possess remarkable continuous operation stability for maximum power point tracking (MPPT) of T90 > 1100 h in ambient air, and damp heat (DH) tracking of T93 > 1400 h.

Amino Pyridine Iodine as an Additive for Defect-Passivated Perovskite Solar Cells.

Defect passivation of the perovskite surface and grain boundary (GBs) has become a widely adopted approach to reduce charge recombination. Research has demonstrated that functional groups with Lewis acid or base properties can successfully neutralize trap states and limit nonradiative recombination. Unlike traditional Lewis acid-base organic molecules that only bind to a single anionic or cationic defect, zwitterions can passivate both anionic and cationic defects simultaneously. In this work, zwitterions organic halide salt 1-amino pyridine iodine (AmPyI) is used as a perovskite for defect passivation. It is found that a pair of amino lone electrons in AmPyI can passivate defects surface and GBs through hydrogen bonding with perovskite, and the introduced I- can bind to uncoordinated Pb2+ while also controlling the surface morphology of the film and improving the crystallinity. In the presence of the AmPyI additive, we obtained about 1.24 µm of amplified perovskite grains and achieved an efficiency of 23.80% with minimal hysteresis.

Flexible All-in-one Quasi-Solid-State Batteries Enabled by Low-water-content Hydrogel Films.

The high conductivities and good mechanical properties of hydrogel electrolyte films are critical for energy storage devices with high flexibility, fast redox kinetics, and long life. Herein, a low water content (6.63 wt%) hydrogel film is prepared, and a favorable environment is created, with an electrochemical stability window of 2.26 V and a high ionic conductivity of 2.6 mS cm-1 . The hydrogel film exhibits good folding ability, low in-plane swelling, and anti-freezing abilities. These properties are benefitted by immobilizing free water molecules on the abundant oxygenic groups of polymer fibers in the hydrogel film, offering a unique 3D channel to allow Li+ to quickly transport along the polymer network. Therefore, the hydrogel film-based all-in-one flexible cell exhibits stable cycling performance with a retention of 81.8% of the initial capacity after 500 cycles at room temperature and 66.2% of capacity retention at -30 °C. Furthermore, the full cell with high cathode loading (≈21 mg cm-2 ) exhibits a high areal capacity of 2.5 mAh cm-2 (≈119 mAh g-1 ). The overall merits of flexible all-in-one quasi-solid-state batteries demonstrate high potential to be used for power wearable electronics.

Dendrimer Modification Strategy Based on the Understanding of the Photovoltaic Mechanism of a Perovskite Device under Full Sun and Indoor Light.

The wide-band-gap inorganic CsPbI2Br perovskite material provides a highly matched absorption range with the indoor light spectrum and is expected to be used in the fabrication of highly efficient indoor photovoltaic cells (IPVs) and self-powered low-power Internet of Things (IoT) sensors. However, the defects that cause nonradiative recombination and ion migration are assumed to form leakage loss channels, resulting in a severe impact on the open-circuit voltage (VOC) and the fill factor (FF) of IPVs. Herein, we introduce poly(amidoamine) (PAMAM) dendrimers with multiple passivation sites to fully repair the leakage channels in the devices, taking into account the characteristics of IPVs that are extremely sensitive to nonradiative recombination and shunt resistance. The as-optimized IPVs demonstrate a promising PCE of 35.71% under a fluorescent light source (1000 lux), with VOC increased from 0.99 to 1.06 V and FF improved from 75.21 to 84.39%. The present work provides insight into the photovoltaic mechanism of perovskites under full sun and indoor light, which provides guidance for perovskite photovoltaic technology with industrialization prospects.

Hole-Transport Management Enables 23%-Efficient and Stable Inverted Perovskite Solar Cells with 84% Fill Factor.

NiOx-based inverted perovskite solar cells (PSCs) have presented great potential toward low-cost, highly efficient and stable next-generation photovoltaics. However, the presence of energy-level mismatch and contact-interface defects between hole-selective contacts (HSCs) and perovskite-active layer (PAL) still limits device efficiency improvement. Here, we report a graded configuration based on both interface-cascaded structures and p-type molecule-doped composites with two-/three-dimensional formamidinium-based triple-halide perovskites. We find that the interface defects-induced non-radiative recombination presented at HSCs/PAL interfaces is remarkably suppressed because of efficient hole extraction and transport. Moreover, a strong chemical interaction, halogen bonding and coordination bonding are found in the molecule-doped perovskite composites, which significantly suppress the formation of halide vacancy and parasitic metallic lead. As a result, NiOx-based inverted PSCs present a power-conversion-efficiency over 23% with a high fill factor of 0.84 and open-circuit voltage of 1.162 V, which are comparable to the best reported around 1.56-electron volt bandgap perovskites. Furthermore, devices with encapsulation present high operational stability over 1,200 h during T90 lifetime measurement (the time as a function of PCE decreases to 90% of its initial value) under 1-sun illumination in ambient-air conditions.

Impermeable Atomic Layer Deposition for Sputtering Buffer Layer in Efficient Semi-Transparent and Tandem Solar Cells via Activating Unreactive Substrate.

Atomic layer deposition (ALD) turns out to be particularly attractive technology for the sputtering buffer layer when preparing the semi-transparent (ST) perovskite solar cells (PSCs) and the tandem solar cells. ALD process turns to be island growth when the substrate is unreactive with the ALD reactants, resulting in the pin-hole layer, which causes an adverse effect on anti-sputtering. Here, p-i-n structured PSCs with ALD SnOx as sputtering buffer layer are conducted. The commonly used electron transportation layer (ETL) PCBM in the p-i-n structured PVK solar cell is an unreactive substrate that prevents the layer-by-layer growth for the ALD SnOx . PCBM layer is activated by introducing reaction sites to form impermeable ALD layers. By introducing reaction sites/ALD SnOx as sputtering buffer layer, the authors succeed to fabricate ST-PSCs and perovskite/silicon (double-side polished) tandem solar cells with power conversion efficiency (PCE) of 20.25% and 23.31%, respectively. Besides, the unencapsulated device with reaction sites maintains more than 99% of the initial PCE after aging over 5100 h. This work opens a promising avenue to prepare impermeable layer for stable PSCs, ST-PSCs, tandem solar cells, and the related scale-up solar cells.

Br Vacancy Defects Healed Perovskite Indoor Photovoltaic Modules with Certified Power Conversion Efficiency Exceeding 36.

Indoor photovoltaics (IPVs) are expected to power the Internet of Things ecosystem, which is attracting ever-increasing attention as part of the rapidly developing distributed communications and electronics technology. The power conversion efficiency of IPVs strongly depends on the match between typical indoor light spectra and the band gap of the light absorbing layer. Therefore, band-gap tunable materials, such as metal-halide perovskites, are specifically promising candidates for approaching the indoor illumination efficiency limit of ∼56%. However, perovskite materials with ideal band gap for indoor application generally contain high bromine (Br) contents, causing inferior open-circuit voltage (VOC ). By fabricating a series of wide-bandgap perovskites (Cs0.17 FA0.83 PbI3- x Brx , 0.6 ≤ x ≤ 1.6) with varying Br contents and related band gaps, it is found that, the high Br vacancy (VBr ) defect density is a significant reason that leading to large VOC deficits apart from the well-accepted halide segregation. The introduction of I-rich alkali metal small-molecule compounds is demonstrated to suppress the VBr and increase the VOC of perovskite IPVs up to 1.05 V under 1000 lux light-emitting diode illumination, one of the highest VOC values reported so far. More importantly, the modules are sent for independent certification and have gained a record efficiency of 36.36%.

Sb2 Se3 Thin-Film Solar Cells Exceeding 10% Power Conversion Efficiency Enabled by Injection Vapor Deposition Technology.

Binary Sb2 Se3 semiconductors are promising as the absorber materials in inorganic chalcogenide compound photovoltaics due to their attractive anisotropic optoelectronic properties. However, Sb2 Se3 solar cells suffer from complex and unconventional intrinsic defects due to the low symmetry of the quasi-1D crystal structure resulting in a considerable voltage deficit, which limits the ultimate power conversion efficiency (PCE). In this work, the creation of compact Sb2 Se3 films with strong [00l] orientation, high crystallinity, minimal deep level defect density, fewer trap states, and low non-radiative recombination loss by injection vapor deposition is reported. This deposition technique enables superior films compared with close-spaced sublimation and coevaporation technologies. The resulting Sb2 Se3 thin-film solar cells yield a PCE of 10.12%, owing to the suppressed carrier recombination and excellent carrier transport and extraction. This method thus opens a new and effective avenue for the fabrication of high-quality Sb2 Se3 and other high-quality chalcogenide semiconductors.

Underwater Multispectral Computational Imaging Based on a Broadband Water-Resistant Sb2Se3 Heterojunction Photodetector.

Exploration, utilization, and protection of marine resources are of great significance to the survival and development of mankind. However, currently classical optical cameras suffer information loss, low contrast, and color distortion due to the absorption and scattering nature for the underwater environment. Here, we demonstrate an underwater multispectral computational imaging system combined with single-photodetector imaging algorithm technology and a CdS/Sb2Se3 heterojunction photodetector. The computational imaging technology coupled with an advanced Fourier algorithm can capture a scene by a single photodetector without spatial resolution that avoids the need to rely on high-density detectors array and bulky optical components in traditional imaging systems. This convenient computational imaging method provides more flexible possibilities for underwater imaging and promises to give more imaging capabilities (such as multispectral imaging, antiscattering imaging capability) to meet ever-changing demand of underwater imaging. In addition, the water-resistant CdS/Sb2Se3 heterojunction photodetector fabricated by the close spaced sublimation (Sb2Se3) and chemical bath deposition (CdS) shows excellent self-powered photodetection performance at zero bias with high LDR of 128 dB, broadband response spectrum range of 300-1050 nm, high responsivity up to 0.47 A/W, and high specific detectivity over 5 × 1012 jones. Compared with the traditional optical imaging system, our designed computational imaging system that combines the advanced Fourier algorithm and a high-performance CdS/Sb2Se3 heterojunction photodetector exhibits outstanding antiscattering imaging capability (shielded by frosted glass), weak light imaging capability (∼0.2 µW/cm2, corresponding to moonlight intensity), and multispectral imaging capability. Therefore, we believe that this work will boost the progress of marine science.

Large-Grain Spanning Monolayer Cu2 ZnSnSe4 Thin-Film Solar Cells Grown from Metal Precursor.

The persistent double layer structure whereby two layers with different properties form at the front and rear of absorbers is a critical challenge in the field of kesterite thin-film solar cells, which imposes additional nonradiative recombination in the quasi-neutral region and potential limitation to the transport of hole carriers. Herein, an effective model for growing monolayer CZTSe thin-films based on metal precursors with large grains spanning the whole film is developed. Voids and fine grain layer are avoided successfully by suppressing the formation of a Sn-rich liquid metal phase near Mo back contact during alloying, while grain coarsening is greatly promoted by enhancing mass transfer during grain growth. The desired morphology exhibits several encouraging features, including significantly reduced recombination in the quasi-neutral region that contributes to the large increase of short-circuit current, and a quasi-Ohmic back contact which is a prerequisite for high fill factor. Though this growth mode may introduce more interfacial defects which require further modification, the strategies demonstrated remove a primary obstacle toward higher efficiency kesterite solar cells, and can be applicable to morphology control with other emerging chalcogenide thin films.

An Embedding 2D/3D Heterostructure Enables High-Performance FA-Alloyed Flexible Perovskite Solar Cells with Efficiency over 20.

Flexible perovskite solar cells (f-PSCs) have attracted increasing attention because of their enormous potential for use in consumer electronic devices. The key to achieve high device performance is to deposit pinhole-free, uniform and defect-less perovskite films on the rough surface of polymeric substrates. Here, a solvent engineering to tailor the crystal morphology of FA-alloyed perovskite films prepared by one-step blade coating is first deployed. It is found that the use of binary solvents DMF:NMP, rather than the conventional DMF:DMSO, enables to deposit dense and uniform FA-alloyed perovskite films on both the rigid and flexible substrates. As a decisive step, an embedding 2D/3D perovskite heterostructure is in situ formed by incorporating a small amount of 4-guanidinobutanoic acid (GBA). Accordingly, photovoltage increases up to 100 mV are realized due to the markedly suppressed nonradiative recombination, leading to high efficiencies of 21.45% and 20.16% on the rigid and flexible substrates, respectively. In parallel, improved mechanical robustness of the flexible devices is achieved due to the presence of the embedded 2D phases. The results underpin the importance of morphology control and defect passivation in delivering high-performance flexible FA-alloyed flexible perovskite devices.

Improving the Photovoltage of Blade-Coated MAPbI3 Perovskite Solar Cells via Surface and Grain Boundary Passivation with π-Conjugated Phenyl Boronic Acids.

High-density electronic defects at the surfaces and grain boundaries (GBs) of perovskite materials are the major contributor to suppressing the power conversion efficiency (PCE) and deteriorating the long-term stability of the solar devices. Hence, the judicious selection of chemicals for the passivation of trap states has been regarded as an effective strategy to enhance and stabilize the photovoltaic performance of solar devices. Here, we systematically investigated the passivation effects of four organic π-conjugated phenylboronic acid molecules: phenylboronic acid, 2-amino phenylboronic acid (2a), 3-amino phenylboronic acid (3a), and 4-amino phenylboronic acid (4a) by adding them into the methylammonium lead iodide (MAPbI3) precursor solution. We found that solar devices with an optimized 5% (mol %) 3a treatment achieve the best passivation effect due to the strong cross-linking ability via hydrogen bonding interactions between the I of the [PbI6]4- octahedral network of perovskite films and the cross-linking terminal groups [-B(OH)2, (-NH2)] of 3a. Moreover, the lone pair of electrons on the N atom of an amino group of 3a can passivate the uncoordinated Pb2+ defects at the surface/GBs. As a result, the 3a-passivated device shows a high open-circuit voltage of 1.13 V, which is a 14.1% improvement compared to the control device (0.99 V). Moreover, the reduced defect density and improved carrier lifetimes enabled a high PCE of 18.89% in our blade-coated champion inverted structure of MAPbI3 solar cells, with improved long-term stability.

Conduction Band Energy-Level Engineering for Improving Open-Circuit Voltage in Antimony Selenide Nanorod Array Solar Cells.

Antimony selenide (Sb2 Se3 ) nanorod arrays along the [001] orientation are known to transfer photogenerated carriers rapidly due to the strongly anisotropic one-dimensional crystal structure. With advanced light-trapping structures, the Sb2 Se3 nanorod array-based solar cells have excellent broad spectral response properties, and higher short-circuit current density than the conventional planar structured thin film solar cells. However, the interface engineering for the Sb2 Se3 nanorod array-based solar cell is more crucial to increase the performance, because it is challenging to coat a compact buffer layer with perfect coverage to form a uniform heterojunction interface due to its large surface area and length-diameter ratio. In this work, an intermeshing In2 S3 nanosheet-CdS composite as the buffer layer, compactly coating on the Sb2 Se3 nanorod surface is constructed. The application of In2 S3 -CdS composite buffers build a gradient conduction band energy configuration in the Sb2 Se3 /buffer heterojunction interface, which reduces the interface recombination and enhances the transfer and collection of photogenerated electrons. The energy-level regulation minimizes the open-circuit voltage deficit at the interfaces of buffer/Sb2 Se3 and buffer/ZnO layers in the Sb2 Se3 solar cells. Consequently, the Sb2 Se3 nanorod array solar cell based on In2 S3 -CdS composite buffers achieves an efficiency of as high as 9.19% with a VOC of 461 mV.

Temperature-Assisted Crystal Growth of Photovoltaic α-Phase FAPbI3 Thin Films by Sequential Blade Coating.

Formamidinium lead triiodide (FAPbI3) exhibits the smallest band gap among lead halide perovskites, which is more desirable for solar cell applications compared to methylammonium-based counterparts. However, it remains a big challenge to prepare phase-pure α-FAPbI3 in addition to controlling the crystal morphology during film formation. Herein, we developed a temperature-assisted crystal growth to prepare high-quality thin films of α-FAPbI3 by sequential blade coating. It is found that depositing organic cation FAI at elevated temperatures facilitates the growth of α-FAPbI3, which otherwise yields mainly a yellow δ-phase at room temperature. In parallel, the crystal morphology of the perovskite films can be effectively manipulated by taking advantage of the porous structure of PbI2. Solar cells prepared with the blade-coated α-FAPbI3 yield a champion efficiency of 18.41%, which is among the highest values for FAPbI3-only solar devices. These results suggest that two-step sequential blade deposition offers a viable approach to fabricate high-quality α-FAPbI3 films for optoelectronic applications.