Explore the vast range of titles available.

All-perovskite tandem solar cells provide high power conversion efficiency at a low cost 1 – 4 . Rapid efficiency improvement in small-area (<0.1 cm 2 ) tandem solar cells has been primarily driven by advances in low-bandgap (approximately 1.25 eV) perovskite bottom subcells 5 – 7 . However, unsolved issues remain for wide-bandgap (> 1.75 eV) perovskite top subcells 8 , which at present have large voltage and fill factor losses, particularly for large-area (>1 cm 2 ) tandem solar cells. Here we develop a self-assembled monolayer of (4-(7 H -dibenzo[ c,g ]carbazol-7-yl)butyl)phosphonic acid as a hole-selective layer for wide-bandgap perovskite solar cells, which facilitates subsequent growth of high-quality wide-bandgap perovskite over a large area with suppressed interfacial non-radiative recombination, enabling efficient hole extraction. By integrating (4-(7 H -dibenzo[ c,g ]carbazol-7-yl)butyl)phosphonic acid in devices, we demonstrate a high open-circuit voltage ( V OC ) of 1.31 V in a 1.77-eV perovskite solar cell, corresponding to a very low V OC deficit of 0.46 V (with respect to the bandgap). With these wide-bandgap perovskite subcells, we report 27.0% (26.4% certified stabilized) monolithic all-perovskite tandem solar cells with an aperture area of 1.044 cm 2 . The certified tandem cell shows an outstanding combination of a high V OC of 2.12 V and a fill factor of 82.6%. Our demonstration of the large-area tandem solar cells with high certified efficiency is a key step towards scaling up all-perovskite tandem photovoltaic technology. A self-assembled monolayer of (4-(7 H -dibenzo[ c,g ]carbazol-7-yl)butyl)phosphonic acid is integrated in wide-bandgap perovskite solar cells, which enables a high power conversion efficiency and low open-circuit voltage deficiency, as well as efficient centimetre-scale all-perovskite tandem solar cells.

Self-assembled monolayers (SAMs) have displayed unpredictable potential in efficient perovskite solar cells (PSCs). Yet most of SAMs are largely suitable for pure Pb-based devices, precisely developing promising hole-selective contacts (HSCs) for Sn-based PSCs and exploring the underlying general mechanism are fundamentally desired. Here, based on the prototypical donor-acceptor SAM MPA-BT-BA (BT), oligoether side chains with different length (i.e., methoxy, 2-methoxyethoxy, 2-(2-methoxyethoxy)ethoxy group) were custom-introduced on the benzothiadiazole unit to produce the target SAMs with acronyms MPA-MBT-BA (MBT), MPA-EBT-BA (EBT), and MPA-MEBT-BA (MEBT), respectively, and acting as HSCs for efficient Sn-Pb PSCs and all-perovskite tandems. The introduction of oligoether side chains enables HSCs effectively accelerate hole extraction, regulate the crystal growth and passivate surface defects of Sn-Pb perovskites. In particular, benefiting from the enhanced Sn-Pb perovskite film quality and the suppressed interfacial non-radiative recombination losses, EBT-tailored LBG devices yield a champion efficiency of 23.54%, enabling 28.61% efficient monolithic all-perovskite tandems with an impressive V OC of 2.155 V and excellent operational stability as well as 28.22%-efficiency 4-T tandems. The development of hole-selective contacts for Sn-based perovskite solar cells is highly desirable. Here, the authors report self-assembled monolayers with oligoether side chains on the benzothiadiazole unit and achieve an efficiency of 28.61% for operationally stable all-perovskite tandems.

The broad bandgap tunability of organic–inorganic metal halide perovskites enables the fabrication of multi-junction all-perovskite tandem solar cells with ultra-high power conversion efficiencies (PCEs). Controllable crystallization plays a crucial role in the formation of high-quality perovskites. Here we report a universal close-space annealing strategy that increases grain size, enhances crystallinity and prolongs carrier lifetimes in low-bandgap (low- E g ) and wide-bandgap (wide- E g ) perovskite films. By placing the intermediate-phase perovskite films with their faces towards solvent-permeable covers during the annealing process, high-quality perovskite absorber layers are obtained with a slowed solvent releasing process, enabling fabrication of efficient single-junction perovskite solar cells (PVSCs) and all-perovskite tandem solar cells. As a result, the best PCEs of 21.51% and 18.58% for single-junction low- E g and wide- E g PVSCs are achieved and thus ensure the fabrication of 25.15% efficiency 4-terminal and 25.05% efficiency 2-terminal all-perovskite tandem solar cells. Controlling the crystallization of perovskites is not trivial. Here Wang et al. develop a close-space annealing to improve the structural and optoelectronic quality of perovskite films with different chemical compositions, leading to over 25% efficiency in all-perovskite tandem solar cells.

The efficiency of all-perovskite tandem solar cells has surpassed that of single-junction perovskite solar cells, yet they still suffer from interfacial non-radiative recombination losses. Charge-selective materials that can reduce such losses as well as fabrication cost “applicable” to both subcells should be developed. Here we design a donor–acceptor-type molecule, MPA2FPh-BT-BA (2F), as a hole-selective contact suitable to both wide-bandgap (WBG) and low-bandgap (LBG) subcells for high-performance all-perovskite tandem solar cells. In the WBG cell, 2F enables efficient hole extraction and minimizes interfacial non-radiative recombination losses by passivating interfacial defects. In the LBG cell, 2F suppresses interfacial losses, regulates the crystal growth and enhances Sn–Pb perovskite film quality. As a result, 2F-treated WBG and LBG devices yield efficiencies of 19.33% (certified 19.09%) and 23.24%, respectively, enabling monolithic all-perovskite tandem solar cells with an efficiency of 27.22% (certified 26.3%) and improved operational stability. Zhu et al. develop a low-cost donor–acceptor-type hole-selective layer that minimizes interfacial non-radiative charge recombination losses in single-junction and tandem solar cells based on metal halide perovskites with different bandgaps.

Multi-junction all-perovskite tandem solar cells are a promising choice for next-generation solar cells with high efficiency and low fabrication cost. However, the lack of high-quality low-bandgap perovskite absorber layers seriously hampers the development of efficient and stable two-terminal monolithic all-perovskite tandem solar cells. Here, we report a bulk-passivation strategy via incorporation of chlorine, to enlarge grains and reduce electronic disorder in mixed tin–lead low-bandgap (~1.25 eV) perovskite absorber layers. This enables the fabrication of efficient low-bandgap perovskite solar cells using thick absorber layers (~750 nm), which is a requisite for efficient tandem solar cells. Such improvement enables the fabrication of two-terminal all-perovskite tandem solar cells with a champion power conversion efficiency of 21% and steady-state efficiency of 20.7%. The efficiency is retained to 85% of its initial performance after 80 h of operation under continuous illumination. Two-terminal monolithic all-perovskite tandem solar cells are attractive due to their flexible nature and low-cost fabrication. Here the authors develop a process to obtain high-quality Sn–Pb perovskite thin films by incorporating chlorine. Such layers are employed to fabricate 20.7%-efficient tandem cells with 80 h operational stability.

Low-bandgap (LBG) mixed tin-lead (Sn−Pb) perovskite solar cells (PSCs) suffer from inferior performance due to their high defect density. Conventionally, ethylenediammonium diiodide (EDADI) is used as a surface passivator to reduce defects and improve device photovoltaic performance, but it introduces severe hysteresis caused by excessive mobilized ions at the top interface. Here, we report a mobile ion suppressing strategy of using hydrazine monohydrochloride (HM) as a bulk passivator to anchor the free ions in LBG perovskites. The protonated hydrazine (N 2 H 5 + ) of HM formed hydrogen bonds with iodine (I – ) ions, while the chloride (Cl – ) ions occupied the I – vacancies, collectively impeding the migration of I – and thus mitigating the ion movement-induced hysteresis that arose from EDADI usage. The synergistic strategy of HM doping and EDADI post-treatment significantly suppresses the oxidation of Sn 2+ , decreases trap density, and inhibits rapid crystallization of perovskite. Consequently, we achieved a champion efficiency of 23.21% for LBG PSCs. Integrating these cells with wide-bandgap PSCs into all-perovskite tandem solar cells yields a high efficiency of 28.55% (certified 28.31%) with negligible hysteresis. The introduction of ethylenediammonium diiodide reduces defects but also leads to severe hysteresis caused by excessive mobilized ions. Here, authors employ hydrazine monohydrochloride as a bulk passivator to mitigate such hysteresis, achieving maximum efficiency of 28.55% for tandem solar cells.

Surface post‐treatment using ammonium halides effectively reduces large open‐circuit voltage (VOC) losses in bromine‐rich wide‐bandgap (WBG) perovskite solar cells (PSCs). However, the underlying mechanism still remains unclear and the device efficiency lags largely behind. Here, a facile strategy of precisely tailoring the phase purity of 2D perovskites on top of 3D WBG perovskite and realizing high device efficiency is reported. The transient absorption spectra, cross‐sectional confocal photoluminescence mapping, and cross‐sectional Kelvin probe force microscopy are combined to demonstrate optimal defect passivation effect and surface electric‐field of pure n = 1 2D perovskites formed atop 3D WBG perovskites via low‐temperature annealing. As a result, the inverted champion device with 1.77‐eV perovskite absorber achieves a high VOC of 1.284 V and a power conversion efficiency (PCE) of 17.72%, delivering the smallest VOC deficit of 0.486 V among WBG PSCs with a bandgap higher than 1.75 eV. This enables one to achieve a four‐terminal all‐perovskite tandem solar cell with a PCE exceeding 25% by combining with a 1.25‐eV low‐bandgap PSC. Tailoring n = 1 pure 2D perovskites on 3D perovskite surface via low‐temperature phenethylammonium bromide (PEABr) post‐treatment strongly suppresses the defects at the grain boundaries of 3D perovskites, which enables a high open‐circuit voltage of 1.284 V and a low open‐circuit voltage loss of 0.486 V for highly efficient inverted 1.77‐eV wide‐bandgap perovskite solar cells.

A wave energy converter features the ability to convert wave energy into the electrical energy required by unmanned devices, and its energy-conversion efficiency is an essential aspect in practical applications. This paper proposes a novel point-absorption wave energy converter with passive morphing blades to meet the demand for improved energy-conversion efficiency. We first introduce its concept and design, with its blades forming their shape by adaptive changes with the direction of the water flow. Next, the three-dimensional geometrical-morphing model, energy-conversion model, and energy-conversion-efficiency model of the wave energy converter were established. Then, the CFD model was built to optimize the design parameters, and the simulation results revealed that the maximum conversion efficiency can be obtained at 90% solidity with 10 blades, a 40–60% load, and 20~25 degrees for the external deflection angle. The simulations also showed that the passive morphing-blade group provides ~40% higher torque and ~60% higher hydraulic efficiency than the flat-blade group.

Mixed‐dimensional perovskites possess unique photoelectric properties and are widely used in perovskite solar cells (PSCs) to improve their efficiency and stability. However, there is a pressing need for a deeper understanding of the physical mechanisms and design principles of mixed‐dimensional PSCs, as such knowledge gaps impose restrictions on unlocking the full potential of this kind of PSC. Herein, a 2D/3D PSC is employed as an example to clarify the working mechanism of mixed‐dimensional PSCs from the perspective of device physics and elaborate on the design rules of high‐efficiency mixed‐dimensional PSCs. Detailed simulation results indicate that the insertion of a layer of 2D perovskite between the 3D perovskite and the hole transport layer (HTL) can significantly reduce the recombination at the HTL/perovskite interface, and PSCs with a 2D/3D perovskite structure exhibit higher tolerance to material selectivity compared with their 3D counterparts. Additionally, the 2D/3D perovskite design can slow down ion migration and accumulation processes, thereby easing the hysteresis behavior of 2D/3D PSCs. Moreover, it is also found that the 2D/3D perovskite structure has a more pronounced effect on improving the efficiency of wide‐bandgap PSCs. Overall, this work sheds new light on mixed‐dimensional PSCs, enabling better guidance for designing high‐efficiency PSCs.

Carbon-based perovskite solar cells (C-PSCs) have the impressive characteristics of good stability and potential commercialization. The insulating layers play crucial roles in charge modulation at the buried perovskite interface in mesoporous C-PSCs. In this work, the effects of three different tunnel oxide layers on the performance of air-processed C-PSCs are scrutinized to unveil the passivating quality. Devices with ZrO2-passivated TiO2 electron contacts exhibit higher power conversion efficiencies (PCEs) than their Al2O3 and SiO2 counterparts. The porous feature and robust chemical properties of ZrO2 ensure the high quality of the perovskite absorber, thus ensuring the high repeatability of our devices. An efficiency level of 14.96% puts our device among the state-of-the-art hole-conductor-free C-PSCs, and our unencapsulated device maintains 88.9% of its initial performance after 11,520 h (480 days) of ambient storage. These results demonstrate that the function of tunnel oxides at the perovskite/electron contact interface is important to manipulate the charge transfer dynamics that critically affect the performance and stability of C-PSCs.