Cesium lead halide perovskite nanocrystals (PNCs) have aroused tremendous research attention because of their excellent optoelectronic properties. Herein, we developed a facile and green low-temperature strategy free of organic solvents, in which only pure water was adopted as the solvent, to synthesize CsPbBr₃ NCs. Intriguingly, although formed with the assistance of water, the obtained CsPbBr₃ NCs present a cubic crystal structure, photoluminescence quantum yield (PLQY) of 75%, and narrow emission line width for bright green emission. Furthermore, both electroluminescence (EL) and photoluminescence (PL)-based light-emitting diodes (LEDs) present intrinsic green emission originating from the as-prepared CsPbBr₃ NCs. Hence, this work offered a novel eco-friendly avenue for the preparation of perovskite NCs for their practical applications in LEDs.

Exploring bifunctional electrocatalysts with high efficiency, inexpensive, and easy integration is still the daunt challenge for the production of hydrogen on a large scale by means of water electrolysis. In this work, a novel free-standing Co ₃ S ₄ /CoMo ₂ S ₄ heterostructure on nickel foam by a facial hydrothermal method is demonstrated to be an effective bifunctional electrocatalyst for overall water splitting (OWS). The synthesized Co ₃ S ₄ /CoMo ₂ S ₄ electrocatalyst achieves ultralow overpotentials of 143 mV@10 mA cm ⁻² for hydrogen evolution reaction (HER) and 221 mV@25 mA cm ⁻² for oxygen evolution reaction (OER), respectively, in 1 M KOH. Moreover, it presents a greatly improved durability and stability under operando electrochemical conditions. When used as catalysts for OWS, the Co ₃ S ₄ /CoMo ₂ S ₄ -3//Co ₃ S ₄ /CoMo ₂ S ₄ -3 electrodes just need 1.514 V to make it to the current density of 10 mA cm ⁻² . It is supposed that the introduction of heterogeneous interface between Co ₃ S ₄ and CoMo ₂ S ₄ could give rise to plentiful active sites and enhanced conductivity, and thus boost excellent catalytic performances. Moreover, the porous feature of free-standing nanosheets on nickel foam could benefits catalytic performances by accelerating charge transport and releasing bubbles rapidly. This work proposes a bifunctional catalyst system with the heterogeneous interface, which could be used in a sustainable green energy system.

Using small size GO as hole injection materials, the fabricated green OLED with Ir(ppy)₃ as emitter achieves the maximum current efficiency, power efficiency, and EQE reaching 73.14 cd A⁻¹, 53.95 lm W⁻¹, and 20.63%, respectively.

We have studied four 2D layered perovskites, including OA ₂ PbI ₄ (RP phase), ODAPbI ₄ and BDAPbI ₄ (DJ phase), (GA)MAPbI ₄ (ACI phase), where OA is [(C _m H _{2 m +1} )NH ₃ ]( m = 8), ODA is [NH ₃ (CH ₂ ) _m NH ₃ ]( m = 8), BDA is [NH ₃ (CH ₂ ) _m NH ₃ ]( m = 4), and GA is [C(NH ₂ ) ₃ ]; RP, DJ, and ACI means Ruddlesden–Popper, Dion–Jacobson and alternating cations in the interlayer, respectively. The temperature dependence of absorption and photoluminescence (PL) spectra have been measured. From which the average phonon energy (electron‐phonon interaction strength) is analyzed as around 34 (80), 47 (184), 50 (402), and 63 (758) with the unit of meV for OA ₂ PbI ₄ , ODAPbI _4, BDAPbI ₄ , and (GA)MAPbI ₄ , respectively. Larger phonon energy indicates the involvement of more phonons in organic spacer layer, with the corresponding stronger electron‐phonon interaction. Furthermore, ultrafast transient absorption spectroscopy proves that, when the excitation photon energy is serval hundred meV higher than bandgap, the excitons still are the major photoexcitations in OA ₂ PbI ₄ , but polarons are major one in ODAPbI ₄ , BDAPbI ₄ , and (GA)MAPbI ₄ films, no matter the excitonic transitions dominate the absorption at their band edges. This work proves the organic spacers can regulate electron–phonon interaction then optoelectronic properties in 2D perovskites profoundly, which have implications toward future rational design for relevant devices.