The components with soft nature in the metal halide perovskite absorber usually generate lead (Pb)0 and iodine (I)0 defects during device fabrication and operation. These defects serve as not only recombination centers to deteriorate device efficiency but also degradation initiators to hamper device lifetimes. We show that the europium ion pair Eu3+-Eu2+ acts as the “redox shuttle” that selectively oxidized Pb0 and reduced I0 defects simultaneously in a cyclical transition. The resultant device achieves a power conversion efficiency (PCE) of 21.52% (certified 20.52%) with substantially improved long-term durability. The devices retained 92% and 89% of the peak PCE under 1-sun continuous illumination or heating at 85°C for 1500 hours and 91% of the original stable PCE after maximum power point tracking for 500 hours, respectively.

luminescence, and also the recent hologram technique. [1-3] Compared to other conventional techniques, the fluorescence printing patterns supply promising high security to the key information valuable documents due to the tunable emission properties. [4,5] As counterfeiting technology has also been quickly developed, the traditional mono-mode anti-counterfeiting is far from the requirement of practical applications to guarantee a high level of data and information safety. The traditional anti-counterfeiting luminescence is achieved by the mono-mode downshifting (DS) luminescence, which converts the high energy photon into lower energy luminescence. To address such concern, developing more complicated anti-counterfeiting techniques by increasing the luminescent modes becomes the most challenging topic. Presently, the realization of concurrent upconversion (UC) and DS have been successfully utilized in anti-counterfeiting based on the lanthanide-based dopants. [6-9] The Eu-doped down-shift luminescent materials have been applied in the Euro banknotes, which enables the visible photoluminescence (PL) based on UV lamp excitation. Meanwhile, the Bank of China also introduced the Yb/Er-doped UC phosphors in the banknotes as the counterfeiting technique, which emits the Anti-counterfeiting techniques have become a global topic since they is correlated to the information and data safety, in which multimodal luminescence is one of the most desirable candidates for practical applications. However, it is a long-standing challenge to actualize robust multimodal luminescence with high thermal stability and humid resistance. Conventionally, the multimodal luminescence is usually achieved by the combination of upconversion and downshifting luminescence, which only responds to the electromagnetic waves in a limited range. Herein, the Yb 3+ /Er 3+ /Bi 3+ co-doped Cs 2 Ag 0.6 Na 0.4 InCl 6 perovskite material is reported as an efficient multimodal luminescence material. Beyond the excitation of ultraviolet light and nearinfrared laser (980 nm), this work extends multimodal luminescence to the excitation of X-ray. Besides the flexible excitation sources, this material also shows the exceptional luminescence performance, in which the X-ray detection limit reaches the level of nGy s −1 , indicating a great potential for further application as a colorless pigment in the anti-counterfeiting field. More importantly, the obtained double perovskite features high stability against both humidity and temperature up to 400 °C. This integrated multifunctional luminescent material provides a new directional solution for the development of multifunctional optical materials and devices.

The hydrogen evolution reaction (HER) usually has sluggish kinetics in alkaline solution due to the difficulty in forming binding protons.Herein we report an electrocatalyst in which sulfur atoms are doping in the oxygen vacancies (V O )of inverse spinel NiFe 2 O 4 (S-NiFe 2 O 4 )t oc reate active sites with enhanced electron transfer capability.T his electrocatalyst has an ultralowo verpotential of 61 mV at the current density of 10 mA cm À2 and long-term stability of 60 ha t1 .0 Acm À2 in 1.0 MKOH media. In situ Raman spectroscopyrevealed that S sites adsorb hydrogen adatom (H*) and in situ form S-H*, which favor the production of hydrogen and boosts HER in alkaline solution. DFT calculations further verified that S introduction lowered the energy barrier of H 2 Od issociation. Both experimental and theoretical investigations confirmed S atoms are active sites of the S-NiFe 2 O 4 .