Hierarchical Nanoarchitectonics of Ultrathin 2D Organic Nanosheets for Aqueous Processed Electroluminescent Devices

Ultrathin 2D organic nanosheets (2DONs) with high mobility have received tremendous attention due to thickness of few molecular layers. However, ultrathin 2DONs with high luminescence efficiency and flexibility simultaneously are rarely reported. Here, the ultrathin 2DONs (thickness: 19 nm) through the modulation of tighter molecular packing (distance: ≈3.31 Å) achievable from the incorporation of methoxyl and dipenylamine (DPA) groups into 3D spirofluorenexanthene (SFX) building blocks is successfully prepared. Even with closer molecular stacking, ultrathin 2DONs still enable the suppression of aggregation quenching to exhibit higher quantum yields of blue emission (Φ_F  = 48%) than that on amorphous film (Φ_F  = 20%), and show amplified spontaneous emission (ASE) with a mediate threshold (332 mW cm^-2 ). Further, through drop-casting method, the ultrathin 2DONs are self-organized into large-scale flexible 2DONs films (1.5 × 1.5 cm) with the low hardness (H: 0.008 Gpa) and low Young's modulus (E_r : 0.63 Gpa). Impressively, the large-scale 2DONs film can realize electroluminescence performances with a maximum luminance (445 cd m^-2 ) and low turn on voltage (3.7 V). These ultrathin 2DONs provide a new avenue for the realization of flexible electrically pumping lasers and intelligent quantum tunneling systems.