Investigating the energy level influence on the stability of phototransistor memory using the poly(siloxane-imide)/perovskite floating gate

Abstract

Perovskite (PVSK) materials have emerged as promising photo-responsive elements in memory devices due to their strong light absorption, simple structure, and non-contact optical programmability. In this study, pentacene was employed as the charge transport layer, MAPbBr₃ nanocrystals as the photoactive memory layer, and siloxane-based polyimides (PIs) as floating-gate dielectrics to modulate energy-level alignment and interfacial properties. Compared with polyamic acid (PAA), which is prone to hydrolysis and thermal degradation, PIs exhibit higher aromatic stability and defect passivation through imide groups, promoting stable PVSK crystal growth. Among the four PI variants, 6FDA-derived PIs contain bulky –CF₃ groups that interrupt conjugation, elevate HOMO energy levels, and increase the bandgap. Shorter siloxane segments further reduce surface energy and enhance interfacial contact, enabling optimal charge storage. The optimized 6FDA-1/PVSK device exhibited excellent photomemory performance under visible illumination (455–656 nm) at an ultralow operating voltage of −1 V, delivering an ON/OFF current ratio of ∼10⁴, a photocurrent ratio of ∼10⁵, stable cycling, and retention exceeding 10⁴ s. The ultralow operating voltage not only reduces power consumption but also offers potential advantages for biological and wearable applications, including enhanced safety, reduced thermal effects, and compatibility with flexible substrates. These results highlight that the low-voltage operation is a key advantage of this design. The findings indicate that molecular engineering of siloxane-based PIs not only stabilizes interfaces but also enables low-power, robust photomemory operation, offering potential for portable and flexible optoelectronic applications.