The built-in potential (Vbi) of an organic diode and solar cell is an important parameter that decides the rectification behavior of organic diodes and affects the open circuit voltage and thereby the efficiency of organic solar cells. In this paper, we propose a physics-based model and an experimental method to extract Vbi from current density-voltage(J-V) characteristics.The proposed model is developed by solving the carrier transport and the continuity equations to obtain the analytic equations for charge carrier profile and current density. The proposed method is thoroughly verified using numerical simulation results. Applicability of thismethod on experimental results is further validated for poly(3-hexylthiophene):phenyl-C61- butyric acid methyl ester solar cells. Finally,Vbi is extracted from dark J-V characteristics of fabricated devices. © 2017 IEEE.