P–N junctions exist in many solid‐state organic devices, such as light‐emitting diodes, solar cells, and thermoelectric devices. Creating P–N junctions by bulk chemical doping in a single organic material (like silicon doped by boron and phosphorus) may capitalize the vast scientific and technological groundwork established in the inorganic semiconducting field. However, high‐performance single‐organic‐material P–N junctions are seldom reported, because the diffusion of the dopant counterions often leads to transient rectification properties. Herein, a new type of lateral fully organic diodes created in single donor–acceptor (D–A) copolymer films with only one P‐type dopant is reported. The achieved lateral devices exhibit high current densities of ≈3.83 A cm−2 and a high rectification ratio of ≈2100, which are beyond the requirements for high‐frequency identification tags. The P‐ to N‐type polarity switching mechanism is proposed after spectroscopic and structural tests. Decent stability of the organic diode is obtained, which is due to the long channel length and low diffusion speed of the large size of dopants. This work opens the opportunities to create P–N junctions in ways of silicon‐based inorganic semiconductors and promises new opportunities for integrating organic materials for flexible and printable organic devices.