In-Depth Study of Ambipolar Charge-Transport Regime through External Triggers and Gas Sensing

Ambipolar devices are a hot topic in research tables due to their unique advantage in reducing the size of the electrical system and enhancing its efficiency. Here, we report a bilayer heterojunction device constructed using octafluoro-vanadyl-phthalocyanine (VOF₈Pc) and lutetium bisphthalocyanine (LuPc₂), which exhibits both p- and n-type behaviors under oxidizing (NO₂ and O₃) and reducing gas (NH₃) species depending on the humidity level and temperature variations. The initial polarity of the device is identified as n-type by measuring a current decrease under oxygen exposure. Most interestingly, we were capable of observing the zero state (no response) where both opposite charge carriers fight for the majority to dominate the electrical properties of the device when it goes from n- to p-type or vice versa. The inversion in the nature of the majority charge carriers in this ambipolar device was achieved by optimizing the external trigger. The unique property of controllable polarity inversion in a VOF₈Pc/LuPc₂-based bilayer heterojunction device makes it the most effective ambipolar device for real-world applications.