Two-Dimensional Polycyclic Photovoltaic Molecule with Low Trap Density for High-Performance Photocatalytic Hydrogen Evolution.

Typical organic semiconductors show a high trap density of states (10 16 -10 18  cm -3 ), providing a large number of centers for charge-carrier recombination, thus hindering the development of photocatalytic hydrogen evolution. Here, we design and synthesize a two-dimensional polycyclic photovoltaic material, named as TPP, to reduce the trap density to as low as 2.3×10 15  cm -3 , which is 1-3 orders of magnitude lower than those of typical organic semiconductors. Moreover, TPP exhibits a broad and strong absorption, ordered molecular packing with a large crystalline coherence length and enhanced electron mobility. Then, the bulk heterojunction nanoparticles (BHJ-NPs) based on a blend of polymer donor (PM6) and TPP exhibit an average hydrogen evolution rate (HER) of 64.31 mmol h -1  g -1 under AM1.5G sunlight (100 mW cm -2 ), and 72.75 mmol h -1  g -1 under 330-1100 nm illumination (198 mW cm -2 ) higher than that of the control NPs based on typical PM6 : Y6 (62.67 mmol h -1  g -1 ).