Phototransistor Organic Field-Effect Transistors (POFETs) are a class of optoelectronic devices that are based on organic semiconductor materials and combine the electrical modulation of field-effect transistors with photoresponse functionality. When exposed to light, the organic semiconductor materials absorb the energy, generating photo-generated carriers, which in turn modulate source-drain current. This enables the conversion of optical signals into electrical signals. POFETs offer high sensitivity, flexibility, and low cost, making them suitable for applications in optical sensors, flexible displays, and biomedical sensors, with vast application potential in other fields as well. In this thesis, two models for estimating the photo-generated carrier concentration based on drain current and photocurrent in POFETs are proposed. To validate the accuracy of these models, six types of POFET devices are fabricated, including those based on lead phthalocyanine (PbPc) and erbium phthalocyanine (ErPc₂) single layers, and CuPc/ErPc₂, pentacene/ErPc₂, C₆₀/PbPc, and pentacene/PbPc/C₆₀ planar heterojunctions. The optoelectronic parameters of these devices are measured. Using the two estimation models, the photo-generated carrier concentrations of different POFET devices are calculated, and the results are comparatively analyzed. This study provides an effective approach for estimating the photogenerated carrier concentration in POFETs.