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Low-temperature activation of oxide semiconductor materials such as In-Ga-Zn-O (IGZO) is a key approach for their utilization in flexible devices. We previously reported that the activation temperature can be reduced to 150 °C by hydrogen-doped IGZO (IGZO:H), demonstrating a strong potential of this approach. In this paper, we investigated the mechanism for reducing the activation temperature of the IGZO:H films. In situ Hall measurements revealed that oxygen diffusion from annealing ambient into the conventional Ar/O2-sputtered IGZO film was observed at >240 °C. Moreover, the temperature at which the oxygen diffusion starts into the film significantly decreased to 100 °C for the IGZO:H film deposited at hydrogen gas flow ratio (R[H2]) of 8%. Hard X-ray photoelectron spectroscopy indicated that the near Fermi level (EF) defects in the IGZO:H film after the 150 °C annealing decreased in comparison to that in the conventional IGZO film after 300 °C annealing. The oxygen diffusion into the film during annealing plays an important role for reducing oxygen vacancies and subgap states especially for near EF. X-ray reflectometry analysis revealed that the film density of the IGZO:H decreased with an increase in R[H2] which would be the possible cause for facilitating the O diffusion at low temperature.

Tandem solar cells offer a pathway beyond the Shockley–Queisser limit of single‐junction devices. Among these, all‐perovskite tandems are especially appealing for their low cost and facile fabrication. However, non‐radiative recombination at the interfaces between perovskite absorbers and charge‐transport layers continues to impede their translation from theoretical potential to experimental realization. Here, we develop a molecular‐design strategy for dual interface engineering of the perovskite photoactive layer, addressing the vertical inhomogeneity inherent to solution‐processed films. We demonstrate that the efficacy of surface modification hinges on matching the alkyl‐chain length of diammonium cations to the local lattice dimensions of each sub‐cell. By applying tailored alkyl diammonium salts to both the top and bottom interfaces, we achieve dramatic reductions in non‐radiative loss, lowered interfacial energy barriers, and suppressed vacancy formation. As a result, the power conversion efficiencies (PCEs) of single‐junction cells improved from 16.7% to 20.5% for the high‐bandgap sub‐cell and from 18.9% to 22.4% for the low‐bandgap sub‐cell. Integration into a monolithic tandem architecture yields a PCE of 27.5%, and the device retains 90% of its initial performance under maximum‐power‐point operation (AM 1.5G, 100 mW cm−2) at room temperature in ambient air for over 500 h. This work establishes a clear, structure‐guided paradigm for interface passivation in perovskite tandems, unlocking both high efficiency and operational durability. Perovskite films were found to require different‐sized passivation molecules at the top and bottom surfaces because crystal spacing varies through the film thickness. With this two‐sided passivation applied to both the high‐ and low‐bandgap layers in an all‐perovskite tandem solar cell, 27.5% efficiency was achieved. The device also demonstrated durability, retaining 90% of its initial power after 500 h of continuous one‐sun operation in air.

Methoxy‐functionalized triphenylamine‐imidazole derivatives that can simultaneously work as hole transport materials (HTMs) and interface‐modifiers are designed for high‐performance and stable perovskite solar cells (PSCs). Satisfying the fundamental electrical and optical properties as HTMs of p‐i‐n planar PSCs, their energy levels can be further tuned by the number of methoxy units for better alignment with those of perovskite, leading to efficient hole extraction. Moreover, when they are introduced between perovskite photoabsorber and low‐temperature solution‐processed NiO x interlayer, widely featured as an inorganic HTM but known to be vulnerable to interfacial defect generation and poor contact formation with perovskite, nitrogen and oxygen atoms in those organic molecules are found to work as Lewis bases that can passivate undercoordinated ion‐induced defects in the perovskite and NiO x layers inducing carrier recombination, and the improved interfaces are also beneficial to enhance the crystallinity of perovskite. The formation of Lewis adducts is directly observed by IR, Raman, and X‐ray photoelectron spectroscopy, and improved charge extraction and reduced recombination kinetics are confirmed by time‐resolved photoluminescence and transient photovoltage experiments. Moreover, UV‐blocking ability of the organic HTMs, the ameliorated interfacial property, and the improved crystallinity of perovskite significantly enhance the stability of PSCs under constant UV illumination in air without encapsulation.

Perovskite solar cells have made significant strides in recent years. However, there are still challenges in terms of photoelectric conversion efficiency and long-term stability associated with perovskite solar cells. The presence of defects in perovskite materials is one of the important influencing factors leading to subpar film quality. Adopting additives to passivate defects within perovskite materials is an effective approach. Therefore, we first discuss the types of defects that occur in perovskite materials and the mechanisms of their effect on performance. Then, several types of additives used in perovskite solar cells are discussed, including ionic compounds, organic molecules, polymers, etc. This review provides guidance for the future development of more sustainable and effective additives to improve the performance of solar cells.

In contrast to conventional ( n – i – p ) perovskite solar cells (PSCs), inverted ( p – i – n ) PSCs offer enhanced stability and integrability with tandem solar cell architectures, which have garnered increasing interest. However, p – i – n cells suffer from energy level misalignment with transport layers, imbalanced transport of photo-generated electrons and holes, and significant defects with the perovskite films. Here we introduce tris(2,4,6-trimethyl-3-(pyridin-3-yl)phenyl)borane (3TPYMB), a nonionic n -type molecule that, through hydrogen bonding and Lewis acid–base reactions with perovskite surfaces or grain boundaries, enables in situ modulation of perovskite energetics, effectively mitigating the key challenges of p – i – n PSCs. The p – i – n PSCs incorporating 3TPYMB achieve a certified quasi-steady-state power conversion efficiency of 24.55 ± 0.33%, with a reverse scan efficiency of 25.58%. They also exhibit exceptional stability, with unencapsulated devices retaining 97.8% of their initial efficiency after 1,800 h of continuous operation at maximum power point under N 2 atmosphere, 1 sun illumination and 60 °C conditions. The introduction of 3TPYMB, an n -type molecule into inverted perovskite solar cells, enables a power conversion efficiency of 25.6%, with devices maintaining up to 98% of the initial efficiency after 1,800 h of operation.

Understanding and preventing oxidative degradation of MXene suspensions is essential for fostering fundamental academic studies and facilitating widespread industrial applications. Owing to their outstanding electrical, electrochemical, optoelectronic, and mechanical properties, MXenes, an emerging class of two-dimensional (2D) nanomaterials, show promising state-of-the-art performances in various applications including electromagnetic interference (EMI) shielding, terahertz shielding, electrochemical energy storage, triboelectric nanogenerators, thermal heaters, light-emitting diodes (LEDs), optoelectronics, and sensors. However, MXene synthesis using harsh chemical etching causes many defects or vacancies on the surface of the synthesized MXene flakes. Defective sites are vulnerable to oxidative degradation reactions with water and/or oxygen, which deteriorate the intrinsic properties of MXenes. In this review, we demonstrate the nature of oxidative degradation of MXenes and highlight the recent advancements in controlling the oxidation kinetics of MXenes with several promising strategic approaches, including careful control of the quality of the parent MAX phase, chemical etching conditions, defect passivation, dispersion medium, storage conditions, and polymer composites.

HighlightsAn effective buried interface stabilization strategy based on synergistic effect of fluorine and sulfonyl functional groups is proposed.The correlations between molecular structures, defect passivation, interfacial energy band alignment, perovskite crystallization and device performance are established.The device with KFSI achieves an impressive efficiency of 24.17%.The interfacial defects and energy barrier are main reasons for interfacial nonradiative recombination. In addition, poor perovskite crystallization and incomplete conversion of PbI2 to perovskite restrict further enhancement of the photovoltaic performance of the devices using sequential deposition. Herein, a buried interface stabilization strategy that relies on the synergy of fluorine (F) and sulfonyl (S=O) functional groups is proposed. A series of potassium salts containing halide and non-halogen anions are employed to modify SnO2/perovskite buried interface. Multiple chemical bonds including hydrogen bond, coordination bond and ionic bond are realized, which strengthens interfacial contact and defect passivation effect. The chemical interaction between modification molecules and perovskite along with SnO2 heightens incessantly as the number of S=O and F augments. The chemical interaction strength between modifiers and perovskite as well as SnO2 gradually increases with the increase in the number of S=O and F. The defect passivation effect is positively correlated with the chemical interaction strength. The crystallization kinetics is regulated through the compromise between chemical interaction strength and wettability of substrates. Compared with Cl−, all non-halogen anions perform better in crystallization optimization, energy band regulation and defect passivation. The device with potassium bis (fluorosulfonyl) imide achieves a tempting efficiency of 24.17%.

All-perovskite tandem solar cells are promising for achieving photovoltaics with power conversion efficiencies above the detailed balance limit of single-junction cells, while retaining the low cost, light weight and other advantages associated with metal halide perovskite photovoltaics. However, the efficiency and stability of all-perovskite tandem cells are limited by the Sn–Pb-based narrow-bandgap perovskite cells. Here we show that the formation of quasi-two-dimensional (quasi-2D) structure (PEA) 2 GAPb 2 I 7 from additives based on mixed bulky organic cations phenethylammonium (PEA + ) and guanidinium (GA + ) provides critical defect control to substantially improve the structural and optoelectronic properties of the narrow-bandgap (1.25 eV) Sn–Pb perovskite thin films. This 2D additive engineering results in Sn–Pb-based absorbers with low dark carrier density (~1.3 × 10 14  cm −3 ), long bulk carrier lifetime (~9.2 μs) and low surface recombination velocity (~1.4 cm s −1 ), leading to 22.1%-efficient single-junction Sn–Pb perovskite cells and 25.5%-efficient all-perovskite two-terminal tandems with high photovoltage and long operational stability. Tong et al. form a 2D perovskite layer with two large organic cations to improve the structural and optoelectronic properties of Sn–Pb perovskites, and eventually the performance of single-junction and tandem solar cells.

Stability and scalability are essential and urgent requirements for the commercialization of perovskite solar cells (PSCs), which are retarded by the non‐ideal interface leading to non‐radiative recombination and degradation. Extensive efforts are devoted to reducing the defects at the perovskite surface. However, the effects of the buried interface on the degradation and non‐radiative recombination need to be further investigated. Herein, an omnibearing strategy to modify buried and top surfaces of perovskite film to reduce interfacial defects, by incorporating aluminum oxide (Al2O3) as a dielectric layer and growth scaffolds (buried surface) and phenethylammonium bromide as a passivation layer (buried and top surfaces), is demonstrated. Consequently, the open‐circuit voltage is extensively boosted from 1.02 to 1.14 V with the incorporation of Al2O3 filling the voids between grains, resulting in dense morphology of buried interface and reduced recombination centers. Finally, the impressive efficiencies of 23.1% (0.1 cm2) and 22.4% (1 cm2) are achieved with superior stability, which remain 96% (0.1 cm2) and 89% (1 cm2) of its initial performance after 1200 (0.1 cm2) and 2500 h (1 cm2) illumination, respectively. The dual modification provides a universal method to reduce interfacial defects, revealing a promising prospect in developing high‐performance PSCs and modules. The aluminum oxide (Al2O3) nanoparticles are imbedded into the buried interface, which fills the voids and grain boundaries of perovskite, leading to compact morphology and reduced dangling bonds and defects. The suppressed trap‐assisted recombination, better energy alignment, and decreased J–V hysteresis in the modified device with Al2O3 nanoparticles and phenethylammonium bromide contribute to a significant increase in voltage and stability.