Solution-Processed Sterically Hindered Donor–Acceptor Small Molecules as Molecular Floating-Gates for High-Efficiency Ambipolar Charge Trapping Memory

The molecular floating-gate transistor memories are fabricated by a simple spinning-coating method using a small-molecule material spiro[fluorene-9,7′-dibenzo[c,h]acridine]-5′-one (SFDBAO) as the trapping element. The molecule with donor–acceptor (D–A) structures contains naphthylamine and quinone-like structures, which can serve as trapping sites for hole and electron integration. Combined with the steric hindrance effect of the molecule itself, the pentacene (PEN)-based transistor memory device with solution-processed SFDBAO shows excellent charge-trapping ability, including high hole trapping efficiency (3.43 × 10¹³ cm⁻² V⁻¹ s⁻¹), fast programming speed (≈1 ms), and ambipolar memory behavior with a large memory window (74.3 V). The optimized device based on the SFDBAO@polystyrene (SFDBAO@PS = 5:1) film exhibits reliable endurance characteristic (>10³ cycles) and good charge retention (>2 × 10⁴ s). These results suggest that the high-performance ambipolar OFET memory can be achieved through a small-molecule material by rational molecular design.