Jun Zhu

The severe nonradiative recombination losses in Cs₂AgBiBr₆ solar cells limit the enhancement of their open circuit voltage (V_OC). Enhancing the built-in electric field (BEF) can help suppress the nonradiative recombination and effectively reduce the V_OC and power conversion efficiency (PCE) losses. In this study, we introduced ferroelectrics diisopropylammonium hydrobromide (DIPAB) as an interfacial layer between the Cs₂AgBi_0.997Fe_0.003Br₆ film and the hole transport layer Spiro-OMeTAD in Cs₂AgBi_0.997Fe_0.003Br₆ solar cells. The ferroelectricity of DIPAB increases the BEF significantly. Additionally, the incorporation of DIPAB effectively passivates the defects and optimizes the energy-level alignment. Ultimately, DIPAB-modified Cs₂AgBi_0.997Fe_0.003Br₆ solar cells achieve a PCE enhancement from 2.81% to 3.43% and yield a V_OC of up to 1.295 V, which is among the highest V_OC documented for Cs₂AgBiBr₆ solar cells to date. Moreover, the unencapsulated DIPAB-modified Cs₂AgBi_0.997Fe_0.003Br₆ solar cells maintain 86% of its initial PCE after aging for 30 days at 25 ± 5 °C and 60 ± 5% relative humidity and 88% after aging for 300 h at 60 °C in a nitrogen glovebox. This study highlights the significance of ferroelectrics in enhancing the performance and stability of Cs₂AgBiBr₆ solar cells.

Dion–Jacobson (DJ) phase halide perovskites have garnered significant attention in photoluminescence applications due to their excellent stability compared to three‐dimensional (3D) perovskites. However, in solution‐processed DJ‐phase perovskite films, the complex crystallization process and the formation of multi‐dispersed quantum well structures significantly impact the optoelectronic properties of the DJ‐phase perovskite. This work presents a quasi‐two‐dimensional (quasi‐2D) mixed‐phase perovskite (MPP) film by introducing Ruddlesden–Popper (RP)‐type aromatic ammonium cations into the DJ‐phase precursor. The resulting MPP _0.2 film, with the chemical formula (PEA ₂ ) _0.2 HDA _0.8 FA ₇ Pb ₈ Br ₂₅ (where HDA = hexamethylenediammonium and PEA = phenylethylammonium), exhibits improved morphology, a more uniform distribution of n phase components, higher crystallinity, and enhanced hydrophobicity compared to the neat DJ‐phase films. Notably, the amplified spontaneous emission (ASE) threshold of the quasi‐2D MPP _0.2 film decreased from 120 to 60 μJ/cm ² . This research shows that quasi‐2D MPP films have great potential as waveguide materials for stable, low‐threshold ASE.

Self-assembled molecules (SAMs) are widely used as hole-selective layers (HSLs) in inverted perovskite solar cells (PSCs). However, its uneven film formation and limited passivation ability for buried interface defects hinder further improvements in device performance. This work introduces sulfadiazine (SD), which contains multifunctional groups, as the interface layer between [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz) and perovskite layers. The SD molecules enhance carrier transport through π-π interactions with the MeO-2PACz. And also, SD also achieves improved energy level alignment, facilitating the transfer of holes at the interface. The N atom on the pyrimidine ring and the O atom in the sulfonamide group of SD can coordinate and bind with Pb²⁺ ions. Additionally, the N atom in the -NH₂ group can form hydrogen bonds (N-H···N) with the FA⁺ ions in the perovskite. The multisite passivation effect significantly reduces nonradiative recombination losses in the device. As a result, devices utilizing SD to modify buried interfaces have achieved a power conversion efficiency (PCE) of 23.27%. Furthermore, the target devices demonstrate excellent thermal stability. This study indicates that using SD as an interface layer is an effective strategy for enhancing the efficiency and stability of PSCs.

Antimony selenosulfide (Sb2(S,Se)3) is a promising quasi-one-dimensional photovoltaic material in the application of solar cell field because of its outstanding optoelectronic properties. It is extremely difficult to achieve the Shockley-Queisser limit due to the presence of various defects and the adverse (hk0) crystal orientation in Sb2(S,Se)3 films. Here, we report an anion-cation synergistic strategy to enhance the quality of Sb2(S,Se)3 films by terbium chloride post-treated process. Both of Tb3+ and Cl- ions are incorporated into the crystal lattice of Sb2(S,Se)3 after post-treatment, which are approved using X-ray photoelectron spectroscopy and X-ray diffraction. This anion-cation synergistic effect promotes the Sb2(S,Se)3 films to have a preferred (hk1) crystal orientation, larger grain size, suppressed deep-level defects and more favorable energy band alignment to facilitate charge carrier transport. Consequently, terbium chloride post-treatment enhances the performance of Sb2(S,Se)3 solar cells, achieving a remarkable of 10.11%. Furthermore, the champion devices exhibit an excellent storage, humidity and thermal stability over 800 h aging test. This work provides a valuable strategy for fabricating high-quality of Sb2(S,Se)3 films and high-efficiency solar cells.

Lewis bases, DMPU, MeIm, and EDA were introduced into the Cs ₂ AgBiBr ₆ precursor solution as solvent additives. MeIm with moderate D _N resulted in dense and uniform Cs ₂ AgBiBr ₆ films and the corresponding solar cells delivered a PCE of 2.61%.

The coupling of superconductivity to unconventional materials may lead to novel quantum states and potential applications. Controlling the quality of the superconductor-normal metal interface is of crucial importance to the understanding and engineering of the superconducting proximity effect. In many cases, conventional lithography-based deposition methods introduce undesirable effects. Using the concept of via contact and dry transfer, we have constructed smooth, van der Waals-like contact between 3D superconducting NbN/Pd and graphene with low contact resistance of approximately 130 Ω μm. Gate-tunable supercurrent, Fraunhofer pattern, and Andreev reflections are observed, the properties of which can be understood using an induced superconducting gap Δ′ in this planar contact geometry. We discuss potential mechanisms impacting the magnitude of Δ′ and suggest ways of further increasing the proximity coupling. This gentle, lithography-free contacting method can be applied to air- and damage-sensitive surfaces to engineer novel superconducting heterostructures.

The crystallization of perovskite films is highly sensitive to environmental conditions and fabrication processes, often leading to defect formation. Precise control over the ordered crystallization of perovskites is crucial for achieving high-performance perovskite solar cells. In this work, we propose a doping strategy using 6-chloropyridine-3-sulfonamide (6-CPS) to modulate perovskite crystallization. The multifunctional 6-CPS molecule, including the sulfonamide group (-SO₂NH₂), pyridine ring (C₅H₅N), and chlorine atom (Cl), enables strong multisite coordination with perovskite components. These unique interactions effectively regulate the perovskite crystallization process, yielding high-quality perovskite films with optimized morphology and reduced defect density. Furthermore, 6-CPS modification improves energy level alignment and enhances the optoelectronic performance of the devices. As a result, the optimized 6-CPS-modified devices achieved a champion power conversion efficiency (PCE) of 24.56%. Notably, the 6-CPS-treated devices exhibit significantly improved stability, retaining 85.44% of their initial PCE after 720 h of accelerated aging under 65 ± 5% relative humidity.

Colloidal nanocrystals (NCs) of fully inorganic perovskites have attracted much attention for their wide optoelectronic applications. Cesium tin halide (CsSnX₃, X= Cl, Br, I) NCs possess the advantage of environmental friendliness. While there have been some reports on the synthesis of CsSnX₃ NCs, the systematic study on turning the size and morphology through reaction temperature and surface ligands is lacking. In this report, CsSnX₃ NCs were synthesized using a hot injection method with three precursors for Cs, Sn and X sources, respectively. We systematically altered the reaction temperature and ligands concentration to investigate their influence on the NC products. Upon decreasing the reaction temperature from 180 °C to 90 °C, the photoluminescence peak underwent a blue shift from 869 nm to 847 nm. Nanorods with a diameter as low as 3 nm were achieved at a lower reaction temperature, while cubic NCs with a size of 15 nm were achieved at the higher reaction temperature. The NCs show an increasing size and a wider distribution with the concentration of oleic acid and oleylamine (OAm) increasing. However, hexagonal Cs₄SnI₆ NCs other than CsSnI₃ NCs will be produced when the OAm concentration is larger than 0.4 M. The study shed a light on the controllable synthesis of Sn-based perovskite NCs.

Alternating cations in the interlayer space (ACI) phase quasi-two-dimensional (quasi-2D) perovskites have garnered significant attention due to their exceptional stability. However, there remains a gap in the power conversion efficiency (PCE) of the corresponding perovskite solar cells (PSCs) when compared to three-dimensional bulk perovskite materials. Herein, an interface passivation strategy involving the spin coating of 1,4-piperazine diethanesulfonic acid salts (PIPES salts) between the ACI phase perovskite (GA)(MA)nPbnI3n+1 (where n = 5, guanidinium = GA, methylammonium = MA) and the self - assembled monolayer (SAM) was presented to passivate the buried bottom interface defects of PSCs. This strategy effectively reduced the surface potential of the SAM, minimized the accumulation of pinholes at the buried bottom interface, and improved the contact between the perovskite layer and the SAM. PIPES salts can interact with perovskite and passivate the crystal defects, thereby reducing non-radiative recombination of carriers. The PSCs passivated by PIPES dipotassium salt achieved a PCE of 15.02%, and their stability was remarkably enhanced. This work underscores the importance of optimizing the buried bottom interface of ACI phase quasi-2D PSCs and offers new insights for the future research.