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The development of highly efficient blue perovskite light‐emitting diodes (PeLEDs) remains a big challenge, requiring more fundamental investigations. In this work, significant photoluminescence enhancement in mixed halide blue perovskite films is demonstrated by using a molecule, benzylphosphonic acid, which eventually doubles the external quantum efficiency to 6.3% in sky‐blue PeLEDs. The photoluminescence enhancement is achieved by forming an oxide‐bonded perovskite surface at grain boundaries and suppressing electron–phonon interaction, which enhances the radiative recombination rate and reduces the nonradiative recombination rate, respectively. Moreover, severe thermal quenching is observed in the blue perovskite films, which can be explained by a two‐step mechanism involving exciton dissociation and electron–phonon interaction. The results suggest that enhancing the radiative recombination rate and reducing the electron–phonon interaction‐induced nonradiative recombination rate are crucial for achieving blue perovskite films with strong emission at or above room temperature. [ABSTRACT FROM AUTHOR]

The cathode interface plays a critical role in achieving high‐performance fullerene/perovskite planar solar cells. Herein, the simple molecule Isatin and its derivatives are introduced at the back contact [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM)/Al as a cathode modification interlayer. It is revealed that the Isatin interlayers facilitate electron transport/extraction and suppress electron recombination, attributed to the formation of negative dipole potential steps and the passivation of the interfacial trap density. The average power conversion efficiencies of the resulting devices are significantly improved by 11% from 17.68% to 19.74%, with an enhancement in all device parameters including short‐circuit current, open‐circuit voltage, and fill factor. The hysteresis index is found to disappear. In addition, such interlayer enhances device stability under ambient conditions compared to the control devices due to suppression of moisture‐induced degradation of the perovskite films. These findings provide a comprehensive understanding of the engineering of the back contact between PCBM and the metal electrode to improve efficiency and stability of perovskite solar cells. [ABSTRACT FROM AUTHOR]

The cationic compositional engineered perovskites undergo severe degradation under illumination in ultrahigh vacuum (UHV) environment. As shown by Jianxin Tang, Qinye Bao and co‐workers in article number 1800262, UHV environment remarkably accelerates the degradation, which delivers the important message that current hybrid perovskite materials and their optoelectronic devices are not suitable for application in outer space (e.g. satellites and probes). [ABSTRACT FROM AUTHOR]

Organometal halide perovskites exhibit a bright future for applications in solar cells, as efficiency has achieved over 22%. The long‐term stability remains a major obstacle for commercialization. Here, it is found that three cationic compositional engineered perovskites, MAPb(I0.83Br0.17)3, FA0.83MA0.17Pb(I0.83Br0.17)3, and Cs0.1(FA0.83MA0.17)0.9Pb(I0.83Br0.17)3, undergo severe degradation under white‐light illumination in ultrahigh vacuum (UHV) environment, but the rate of degradation is significantly lower for the mixed cation perovskites. This is attributed to the defect‐induced trap states that trigger the strong coupling between the photoexcited carriers and the crystal lattice. The observed behavior supports the view of the mixed cations suppressing the photoinduced degradation. It is further demonstrated that UHV environment remarkably accelerates the degradation of the perovskite films under illumination, which delivers a very important message that the current hybrid perovskite materials and their optoelectronic devices are not suitable for application in outer space. Moreover, the applied UHV environment can be an accelerated test method to estimate the photostability of the perovskites. Photostability of mixed cation perovskite films in extreme environment is unraveled through ultrahigh vacuum (UHV) environment that simulates outer space. UHV remarkably accelerates the degradation of the perovskite films under white illumination, and it can be used as an accelerated test method to estimate the photostability of perovskites. [ABSTRACT FROM AUTHOR]