Unencapsulated Self-Hydroadaptive Organic Heterojunctions for Underwater Physiological Monitoring.
basic_science · Level V
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- Record sourced from PubMed, PMID 42728558.
- Also identified by DOI 10.1002/adma.74922.
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Abstract
Water exposure is generally considered detrimental to organic semiconductor films, causing irreversible defects, dielectric perturbation, and device failure. Here, n-type giant-molecule-type organic semiconductors GSY-C4 and GSY-C10 with tailored alkyl chains were developed for waterproof organic photodetectors (OPDs). D18:GSY-C4 and D18:GSY-C10 bulk heterojunctions enabled stable underwater photoplethysmography sensing, with peak responsivities of ∼1.31 and ∼0.7 A W<sup>-1</sup>, respectively. Short-term water exposure did not cause obvious irreversible degradation, but induced water-triggered adaptive structural reorganization, supported by reduced lamellar d-spacing, increased lamellar coherence length, and preserved π-π stacking. After 4 h water immersion, unencapsulated D18:GSY-C4 arrays (n = 49) showed a ∼9% reduction in dark-current density and nearly unchanged responsivity (R<sub>λ</sub>) and specific detectivity (D*). Moreover, key current parameters could be recovered through ethanol rinsing and mild annealing at 100°C for 20 min. D18:GSY-C10 OPDs maintained underwater functionality for 9 days with <10% variation in dark- and photocurrent densities, highlighting alkyl-chain engineering as an effective strategy for aqueous-stable organic optoelectronics.