Within light sensing optoelectronic devices, multijunction organic and hybrid photodetectors show a large potential. In particular, organic and hybrid phototransistors hold promises for high-sensitivity thanks to their inherent signal-amplification characteristics. However, often a trade-off between a large sensing area, a fast response, and a high specific detectivity is difficult to be achieved. Here we propose an alternative phototransistor concept, that relies on a geometrically engineered large area tri-channel architecture, applied to a multilayer hybrid phototransistor composed of an inorganic In2O3/ZnO n-type field-effect channel, and a top organic bulk-heterojunction or hybrid perovskite light-sensing layer. Up-scalable solution-processing of both the field-effect channel and the light-sensing layers are implemented. Different photoactive layers are used to corroborate and validate the proposed concept. The resulting phototransistor combines the characteristics of easy solution processing, a maximum responsivity of 10^5 A/W thanks to the large electron mobility of the In2O3/ZnO heterointerface, and a maximum specific detectivity of 10^15Jones (at a low gate voltage of 5V and under a low light illumination of 10 nW/cm2), thanks to the large sensing area which is fully exploited in the tri-channel architecture. The improved photoresponse characteristics are accompanied by a fast response (risetime <10ms down to the uW/cm2 of illumination), which is comparable to the time-response of analogous phototransistors in the conventional architecture. The experimental data are supported by device modelling, which helps highlighting the peculiar advantages of the proposed large area, tri-channel and multi-junction phototransistor architecture.
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