Flexible Phototransistors Integrated with Chiral Liquid Crystal Encapsulating Film for Improving Color Selectivity and Stability

Organic phototransistors (OPTs), which have optical signal detection, signal amplification, and mechanical flexibility, are fundamental building blocks of flexible and wearable optoelectronics. For the practical application of the OPTs, color selectivity for accurate optical signal processing is essential. Additionally, a high electrical stability should be guaranteed against environmental factors. Here, we propose a flexible OPT that achieves both color selectivity and environmental stability through a single encapsulating layer made of a chiral liquid crystal (CLC) polymer. This CLC polymer has a unique optical property called selective wavelength reflection, which can be precisely tailored to the color selectivity of the OPTs. Additionally, the CLC film demonstrates moisture resistance, allowing the proposed device to operate stably under ambient conditions. This multifunctional encapsulating layer is integrated on the OPT through a simple transfer process. The straightforward yet effective concept of integrating CLC films into OPTs is expected to provide a platform for the development of next-generation flexible optoelectronic devices.