Harnessing the Piezo-Phototronic Effect in Flexible Chiral Organic Single Crystals for Light-Responsive Tactile...

The piezo-phototronic effect arises from the interaction between mechanical stress, driven by the piezoelectric effect, and light, which induces the phototronic effect, ultimately influencing the electronic properties of a material. When the piezoelectric and phototronic effects combine, the resulting piezo-phototronic effect imparts enhanced or tunable properties to optoelectronic devices that respond to both light and mechanical strain. While inorganic materials are widely studied for piezo-phototronic properties, organic materials present more attractive alternatives due to their modular properties, and cost-effectiveness. Flexible organic single crystals are well-suited for optoelectronic device fabrication due to their defect-free structure and well-ordered packing, which enhances device performance. Despite these advantages, the simultaneous integration of photoexcitation, semiconductor functionality, and piezoelectricity, the foundation of the piezo-phototronic effect, remains unexplored in flexible organic single crystals. Here, we report the discovery of a mechanically flexible single crystal exhibiting the piezo-phototronic effect. The molecular design strategy played a crucial role, wherein the incorporation of chiral and light-absorbing moieties imparts piezo- and phototronic properties, respectively. The flexible crystals are further used to fabricate a piezo-phototronic device, which demonstrates exceptional strain-dependent photocurrent modulation and a high detection sensitivity of ∼158%. Furthermore, the piezo-phototronic device could distinguish between light and dark conditions and respond to mechanical stress, thereby highlighting its multipurpose sensing capabilities. The enhanced response under light exposure also suggests promising applications in wearable technology for human-machine interfaces and health monitoring, where the simultaneous sensing of light and mechanical deformation is crucial for improved functionality and performance.