Detachable Top Electrode-Organic Photodetector for Repeated Nondestructive Evaluation of Device Performance and Surface Analysis of the Active Layer

Organic photodetectors (OPDs) are key devices for monitoring vital signs, such as heart rate and blood oxygen level. For realizing the long-term measurement of biosignals, stable operation is essential. To improve the stability of OPDs, it is important to analyze each layer to understand the degradation mechanism. We developed detachable top electrode (DTE)-OPDs to enable both surface analysis of the active layer and device characterization to be performed nondestructively and repeatedly within a single device. The substrate of the top electrode is a 2 μm thick elastomer sheet reinforced with polyurethane nanofibers. The DTE-OPDs showed a Dsh* of 1.4 × 1012 Jones by attaching the top electrodes to the bottom stack without external pressure. The DTE-OPDs showed no degradation after 1000 attaching/detaching cycles of the top electrodes. Using the DTE-OPDs, we successfully observed the relationship between dark current increase and oxidization of the active layer.