Structurally Flexible 2D Spacer for Suppressing the Electron-Phonon Coupling Induced Non-Radiative Decay in Perovskite Solar Cells

This study presents experimental evidence of the dependence of non-radiative recombination processes on the electron-phonon coupling of perovskite in perovskite solar cells(PSCs).Via A-site cation engineering,a weaker electron-phonon coupling in perovskite has been achieved by introducing the structurally soft cyclohexane methylamine(CMA^(+))cation,which could serve as a damper to alleviate the mechanical stress caused by lattice oscillations,compared to the rigid phenethyl methylamine(PEA^(+))analog.It demonstrates a significantly lower non-radiative recombination rate,even though the two types of bulky cations have similar chemical passivation effects on perovskite,which might be explained by the suppressed carrier capture process and improved lattice geometry relaxation.The resulting PSCs achieve an exceptional power conversion efficiency(PCE)of 25.5%with a record-high opencircuit voltage(V_(OC))of 1.20 V for narrow bandgap perovskite(FAPbI_(3)).The established correlations between electron-phonon coupling and non-radiative decay provide design and screening criteria for more effective passivators for highly efficient PSCs approaching the Shockley-Queisser limit.

Two-photon 3D printed spring-based Fabry-Pérot cavity resonator for acoustic wave detection and imaging

Optical fiber microresonators have attracted considerable interest for acoustic detection because of their compact size and high optical quality.Here,we have proposed,designed,and fabricated a spring-based Fabry-Pérot cavity microresonator for highly sensitive acoustic detection.We observed two resonator vibration modes:one relating to the spring vibration state and the other determined by the point-clamped circular plate vibration mode.We found that the vibration modes can be coupled and optimized by changing the structure size.The proposed resonator is directly 3D printed on an optical fiber tip through two-photon polymerization and is used for acoustic detection and imaging.The experiments show that the device exhibits a high sensitivity and low noise equivalent acoustic signal level of 2.39 mPa∕Hz^(1∕2)at 75 kHz that can detect weak acoustic waves,which can be used for underwater object imaging.The results demonstrate that the proposed work has great potential in acoustic detection and biomedical imaging applications.