Rhodamine 6G and phloxine B as photosensitizers for inkjet-printed indium oxide phototransistors

Indium oxide (In₂O₃) can be employed as an active semiconductor component in phototransistor devices. However, the large bandgap of In₂O₃ restricts its wavelength detection range to blue or UV light. Therefore, methods are required to facilitate detection of longer wavelengths. To this end, this work demonstrates the encapsulation of rhodamine 6G or phloxine B organic dye within a matrix of In₂O₃ semiconductor, to form a composite photosensitizing material that is patterned by the scalable fabrication pathway of inkjet-printing. This composite material is found to enhance the optoelectronic performance of inkjet-printed In₂O₃ thin film transistors in response to green light (565 nm). Specifically, the devices containing a rhodamine 6G/InO_x composite top layer present good electrical performance in the dark with saturation mobility of 6.36 cm² V⁻¹ s⁻¹ and, under green light illumination, photosensitivity of 4.1 × 10⁵, and responsivity of 250 A W⁻¹. Its photoconductive state is returned to the initial condition by applied positive gate voltage pulse. The approach presented in this work could be applied for production of large area optoelectronics to enable applications such as displays, photo-memory, or dosimetry.