Modeling Light propagation within human head to deduce spatial sensitivity distribution (SSD) is important for Near-infrared spectroscopy (NIRS)/imaging (NIRI) and di®use correlation tomography. Lots of head models have been used on this issue, including layered head model, arti¯cial simpli¯ed head model, MRI slices described head model, and visible human head model. Hereinto, visible Chinese human (VCH) head model is considered to be a most faithful presentation of anatomical structure, and has been highlighted to be employed in modeling light propagation. However, it is not practical for all researchers to use VCH head models and actually increasing number of people are using magnet resonance imaging (MRI) head models. Here, all the above head models were simulated and compared, and we focused on the e®ect of using di®erent head models on predictions of SSD. Our results were in line with the previous reports on the e®ect of cerebral cortex folding geometry. Moreover, the in°uence on SSD increases with thē delity of head models. And surprisingly, the SSD percentages in scalp and gray matter (region of interest) in MRI head model were found to be 80% and 125% higher than in VCH head model. MRI head models induced nonignorable discrepancy in SSD estimation when compared with VCH head model. This study, as we believe, is the¯rst to focus on comparison among full serials of head model on estimating SSD, and provided quantitative evidence for MRI head model users to calibrate their SSD estimation.

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Organic photodiodes (OPDs) have been the subject of extensive research due to their inherent advantages of largearea detection, wide range of material selection and low-cost fabrication. Near infrared (NIR) OPDs were realized mainly by using narrow energy-gap materials and doping organic NIR dyes into the active layer. Here we report on realization of NIR OPDs by exploiting the exciplex absorption in heterojunction consisting of neodymium phthalocyanine (NdPc2) and C60. For NIR OPDs based on NdPc2/C60 planar heterojunction with C60 thickness of 50 nm, the optimal NdPc2-layer thickness for specific detectivity is 30 nm, while that for photoresponsivity is smaller than 10 nm. A maximal specific detectivity of ~4.46×10 9 Jones was obtained at the optimized NdPc2 layer thickness of 30 nm. At NdPc2 layer thickness of 10 nm, a maximal photoresponsivity of 60 mA/W and a maximal external quantum efficiency (EQE) of 17% were obtained. The results presented here demonstrate that utilizing exciplex absorption in heterojunction based on NdPc2 and C60 is a prospective route for realizing NIR OPDs.

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