<p>The wide range of materials, fabrication processes and structures complicates the development of a compact model for organic thin-film transistors (OTFTs). Experimental comparisons indicate that enhanced modelling is required to predict and explain the behaviour of organic semiconductors, particularly concerning electrostatics and structural interactions. The research suggests compact DC models are essential for modelling and improving organic devices. Various analytical models are used since a single model cannot include all materials and processes. A charge drift model generates reliable current-voltage (I-V) characteristics, then transforms into a symmetrical compact DC model incorporating sub-threshold behaviour, contact resistance, and channel length modulation to enhance electrical performance and get realistic behaviour. Further, the variation of biomolecule immobilization in the cavity of the proposed biosensor is analyzed along with drain voltage, gate voltage, contact resistance (R_c), mobility enhancement factor (γ), linear-to-saturation factor (m), etc. The proposed biosensor has a drain current sensitivity of 26.93 and a transconductance sensitivity of 15.068 for k = 12, respectively. The findings are validated through small-molecule OFET measurements, offering valuable perspectives for upcoming OTFT modelling endeavours, particularly in health sector applications, the medical field, and environmental monitoring.</p>