Refined Signal Organic Photodetectors via Transfer Lamination of pH-Controlled PEDOT:PSS for Durable In Situ Stress Monitoring

This paper presents a strategy for noise suppression and stability enhancement of organic photodetectors (OPDs) by introducing pH-neutralized and transfer-laminated poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the hole-transporting layer (HTL). Although PEDOT:PSS is widely used as an HTL material, its intrinsic acidity and structural instability hinder the performance of the OPD. Here, imidazole-induced neutralization promotes a linear entangled structure, while transfer lamination enables controlled PSS domain distribution. These structural modifications lead to a favorable energy level alignment for hole transport and improved HTL stability. Enhanced interfacial contact between the photoactive layer and HTL facilitates photocurrent flow and reduces internal noise, yielding high specific detectivity and shot-noise-limited detectivity without bias and under -0.5 V reverse bias. The optimized OPD device also exhibits increased shunt resistance, reduced trap density, and fast response to frequency-specific optical signals with high signal-to-noise and wide frequency bandwidth. An in situ stress monitoring system demonstrates the device's capability for real-time bio signal detection, maintaining stable operation after 360 h of ambient storage. These results confirm the potential use of pH-controlled, transfer-laminated PEDOT:PSS for high-performance, long-term stable OPDs in practical sensing applications.