Introduction of helical photonic crystal insulator in organic phototransistor for enhancing selective color absorption

Organic phototransistors, with their electrically adjustable photo-sensing characteristics and mechanical flexibility, are promising components of multifunctional optoelectronics. For practical applications of the optoelectronics, it is essential to develop organic phototransistors with high photo-sensing performances and wavelength selectivity. Although, several studies have been conducted on improving the photo-sensing performances of organic phototransistors through the molecular engineering of organic materials, achieving improved light absorption and stable electrical performance remains a challenge. Here, we propose a new organic phototransistor structure that improves photo-sensing performances and wavelength selectivity by introducing helical photonic crystal (HPC) insulators. To realize the HPC film acting as a reliable insulator and an effective blue-wavelength reflector, a numerical analysis is performed. In the developed device, the blue light transmitting the semiconductor medium is effectively reflected by the HPC insulator, thereby improving the absorption of blue light in the channel region. Our device exhibits higher photo-sensing performances than the reference device without HPC film in terms of photosensitivity, photoresponsivity, and blue-wavelength selectivity. This novel concept of improving the wavelength selectivity of organic phototransistors will become an effective part of the development of practical photodetectors related to next-generation light and image sensors.