High operation stability and different sensing mechanisms in graphene oxide gel photodetectors utilizing a thin polymeric layer

We report a significant improvement in the operational stability and photosensitivity of an interdigitated photodetector using a hybrid sensing material based on a reduced graphene oxide gel (femtogel) and poly methyl methacrylate (PMMA). By coating the reduced graphene oxide photodetector with a protective layer of PMMA, a noticeable current stability is achieved, either during a sweep or fixed voltage, compared to an unprotected photodetector. A bolometric-effect sensing mechanism was observed in the unprotected photodetector, whereas the hybrid PMMA/femtogel photodetector displayed a photovoltaic-effect sensing mechanism. This change in the sensing mechanism of the graphene-based device, as a result of encapsulating the sensing area using a polymeric thin layer, is reported for the first time. Moreover, a higher and reliable sensitivity to the low-power illumination source was observed in the hybrid PMMA/femtogel photodetector. This study provides an avenue for engineering the performance and reliability of graphene oxide photodetectors that operate in an ambient environment in order to solve the current bottleneck issue, resulting from the lack of reliability, in commercializing these materials.