Compact Modeling of Near-Infrared Heterojunction Organic Phototransistors Based on Tin Phthalocyanine

Rapid progress has been achieved in experimental research of heterojunction organic phototransistors (HJ-OPTs); however, a model that captures essential physical phenomena occurring in HJ-OPTs is still lacking. Herein, we developed a compact model for HJ-OPTs by associating the excitonic photocarrier generation, the approach of equivalent the effect of light illumination as an additional gate voltage, and the power law dependence of photocarrier sheet density on light intensity with the generic 1-D charge drift theory for organic field-effect transistors (OFETs). The model can describe the output and transfer characteristics of HJ-OPTs both in the dark and under illumination. We fabricated and characterized an HJ-OPT based on C60/tin phthalocyanine (SnPc), and calculated its output and transfer characteristics, as well as photoresponsivity with the developed model. Excellent agreements between experiment and model fitting were obtained with the exception of the dark output curves in the case of high drain and gate voltages. Extending the model by incorporating the short-channel effect (SCE) and contact resistance effect, the imperfectness could be completely eliminated. The validation results showed that this model can be effectively applied to HJ-OPTs, which is of great significance for optimizing their performance in the future.