Interface-guided twisted stacking of two-dimensional organic molecular crystals for polarization-reoriented emission

Abstract

The controlled vertical assembly of organic molecular crystals remains challenging because weak intermolecular interactions often lead to random nucleation and unpredictable stacking orientations. Here we report an interface-guided vapor-phase assembly strategy for constructing stacked two-dimensional organic molecular crystals with controlled stacking geometry and layer thickness. This approach enables two distinct stacking modes: lattice-matched parallel heterostacking in DPQ-DPFQ crystals (P-OCs) and energetically favored 80° twisted homostacking in DPFQ bilayers (T-OCs), with T-OCs accounting for 54.3 ± 3.8% of the counted crystals across six independent substrates under optimized growth conditions. The fixed-angle twisted stacking couples misaligned optical axes from adjacent layers, producing lateral and vertical waveguide resonance coupling and thickness-programmed polarization reorientation. By increasing the upper layer thickness from 530 to 935 nm, the output polarization angle is continuously shifted from 45° to 74°. This work establishes molecular interface-guided twisting as a structural strategy for encoding passive polarization outputs in organic crystalline photonic materials.