Low Operating Voltage Solution Processed (Li₂ZnO₂) Dielectric and (SnO₂) Channel-Based Medium Wave UV-B Phototransistor for Application in Phototherapy

Abstract

UV lamps used for phototherapy for the treatment of several skin diseases do not have uniform output. This makes the treatment difficult and less responsive. A Ultraviolet B (UV-B) sensitive thin-film phototransistor has been fabricated and characterized to monitor the intensity of UV radiation in phototherapy of skin diseases like psoriasis, vitiligo, and atopic dermatitis. Phototherapy with UV-B ranges from 280 to 320 nm, safe and very effective for skin disease treatment. Hence, to make it portable and affordable for medical technologies, we have demonstrated the fabrication process of a low-operational (≤2V), low-cost solution-processed Li2ZnO2 (dielectric)/SnO2 (channel)-based phototransistor that shows very high photosensitivity at around ~300 nm of UV-B region. The working principle depends on the passage of UV-B light through a window followed by striking a micrometer-scale semiconductor phototransistor. The responsivity and external quantum efficiency (EQE) of the fabricated phototransistor was found to be about 0.12 A/W and 40.12% at 300 nm, respectively, at a notably low operating voltage (≤2 V). High sensitivity (>200%) with fast response time (7 s) was also achieved with UV-B irradiation of 650 $\mu \text{W}$ /cm2. For in-depth performance analysis of the fabricated device, modeling has also been done, and the outcome matched well with the experimental results.