Effects of Self-Assembly and Molecular Arrangement in Organic Semiconductor Device Applications

Organic photomemory offers a promising pathway for next-generation multifunctional optoelectronics. This research systematically investigates the correlation between molecular arrangement boundaries and macroscopic memory performances. The first work demonstrates a multi-level, nonvolatile organic photomemory featuring optical rewritability engineered by utilizing oriented rod-like organic molecules, specifically C8-PDI. By manipulating the side-chain-induced self-assembly and molecular packing, we establish a robust structural baseline for efficient charge trapping and localized carrier storage. Building upon this, the second work advances from spontaneous self-assembly to engineered lamellar heterojunctions by introducing functional interlayers. We construct multi-layer architectures incorporating electron-transporting (PDIN) and hole-blocking (BCP) layers into the C8-PDI matrix. Biexponential transient photocurrent analysis reveals that while PDIN accelerates interfacial charge extraction via interfacial dipoles, the deep HOMO level of BCP acts as a profound hole-blocking boundary. This engineered interface effectively reshapes the trap density of states, reallocating photogenerated carriers into deep traps. Consequently, the multi-layer C8-PDI/BCP architecture achieves exceptional long-term memory retention without sacrificing the threshold voltage. Together, these works elucidate a comprehensive "structural boundary engineering" strategy—from intrinsic morphological control to artificial interfacial energy modulation—paving the way for high-performance, optically programmable nonvolatile logic circuits.