Ultrafast Photoexcitation Induced Passivation for Quasi-2D Perovskite Photodetectors.

Quasi-2D perovskites exhibit great potential in photodetectors due to their exceptional optoelectronic responsivity and stability, compared to their 3D counterparts. However, the defects are detrimental to the responsivity, response speed, and stability of perovskite photodetectors. Herein, an ultrafast photoexcitation-induced passivation technique is proposed to synergistically reduce the dimensionality at the surface and induce oxygen doping in the bulk, via tuning the photoexcitation intensity. At the optimal photoexcitation level, the excited electrons and holes generate stretching force on the Pb─I bonds at the interlayered [PbI6]-, resulting in low dimensional perovskite formation, and the absorptive oxygen is combined with I vacancies at the same time. These two induced processes synergistically boost the carrier transport and interface contact performance. The most outstanding device exhibits a fast response speed with rise/decay time of 201/627 ns, with a peak responsivity/detectivity of 163 mA W-1/4.52 × 1010 Jones at 325 nm and the enhanced cycling stability. This work suggests the possibility of a new passivation technique for high performance 2D perovskite optoelectronics.

Photoexcitation-induced passivation of SnO2 thin film for efficient perovskite solar cells.

A high-quality tin oxide electron transport layer (ETL) is a key common factor to achieve high-performance perovskite solar cells (PSCs). However, the conventional annealing technique to prepare high-quality ETLs by continuous heating under near-equilibrium conditions requires high temperatures and a long fabrication time. Alternatively, we present a non-equilibrium, photoexcitation-induced passivation technique that uses multiple ultrashort laser pulses. The ultrafast photoexcitation and following electron-electron and electron-phonon scattering processes induce ultrafast annealing to efficiently passivate surface and bulk defects, and improve the crystallinity of SnO2, resulting in suppressing the carrier recombination and facilitating the charge transport between the ETL and perovskite interface. By rapidly scanning the laser beam, the annealing time is reduced to several minutes, which is much more efficient compared with conventional thermal annealing. To demonstrate the university and scalability of this technique, typical antisolvent and antisolvent-free processed hybrid organic-inorganic metal halide PSCs have been fabricated and achieved the power conversion efficiency (PCE) of 24.14% and 22.75% respectively, and a 12-square-centimeter module antisolvent-free processed perovskite solar module achieves a PCE of 20.26%, with significantly enhanced performance both in PCE and stability. This study establishes a new approach towards the commercialization of efficient low-temperature manufacturing of PSCs.

Passive Deicing CFRP Surfaces Enabled by Super-Hydrophobic Multi-Scale Micro-Nano Structures Fabricated via Femtosecond Laser Direct Writing.

Carbon fiber reinforced plastic (CFRP) is the main material of aircraft skin. Preparing superhydrophobic anti-icing/deicing surface on the CFRP is of great importance for aircraft flight safety. In this work, a variety of multi-scale micro-nano structures were imprinted on CFRP by femtosecond laser processing, and a transition from hydrophilic to superhydrophobic CFRP was realized. After being optimized by different geometries and laser conditions, the water contact angle, which is tested at 24.3 °C and 34% humidity, increased from 88 ± 2° (pristine) to 149 ± 3° (100 µm groove) and 153 ± 3° (80 µm grid). A further anti-icing test at -10 °C (measured on the cooling platform) and 28% humidity showed that the freezing time was increased from 78 ± 10 s (pristine) to 282 ± 25 s (80 µm grid). Most importantly, the tensile tests showed that the femtosecond laser processing method did not deteriorate the mechanical properties of CFRP. This work provides great significance for aircraft passive deicing technology.