Molecule Charge Transfer Doping for p‐Channel Solution‐Processed Copper Oxide Transistors

Abstract The doping of semiconductors plays a critical role in improving the performance of modern electronic devices by precisely controlling the charge carrier density. However, the absence of a stable doping method for p‐type oxide semiconductors has severely restricted the development of metal oxide‐based transparent p–n junctions and complementary circuits. Here, an efficient and stable doping process for p‐type oxide semiconductors by using molecule charge transfer doping with tetrafluoro‐tetracyanoquinodimethane (F 4 TCNQ) is reported. The selections of a suitable dopant and geometry play a crucial role in the charge‐transfer doping effect. The insertion of a F 4 TCNQ thin dopant film (2–7 nm) between a Au source‐drain electrode and solution‐processed p‐type copper oxide (Cu x O) film in bottom‐gate top‐contact thin‐film transistors (TFTs) provides a mobility enhancement of over 20‐fold with the desired threshold voltage adjustment. By combining doped p‐type Cu x O and n‐type indium gallium zinc oxide TFTs, a solution‐processed transparent complementary metal‐oxide semiconductor inverter is demonstrated with a high gain voltage of 50. This novel p‐doping method is expected to accelerate the development of high‐performance and reliable p‐channel oxide transistors and has the potential for widespread applications.