High‐Miscibility n‐Dopant for Organic Semiconductors Enabling Highly Stable Organic Transistors

Abstract Doping plays a crucial role in tuning the electrical properties of organic semiconductors (OSCs), yet n‐doping presents more challenges than p‐doping. A significant limitation is the poor miscibility between n‐dopants and OSCs, which hinders the practical application of n‐doping in high‐performance devices. Herein, a novel n‐dopant, 2,8,9‐Trimethyl‐2,5,8,9‐tetraaza‐1‐phosphabicyclo‐[3.3.3]undecane (TMP) is introduced, which exhibits exceptional miscibility with OSCs while maintaining excellent doping performance comparable to the benchmark n‐dopant 4‐(2,3‐Dihydro‐1,3‐dimethyl‐1H‐benzimidazol‐2‐yl)‐N, N‐dimethylbenzylamine (N‐DMBI). TMP effectively dopes gNDI‐BT, poly[[N, N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)] (N2200) and [6,6]‐phenyl‐C 61 ‐butyric acid methyl ester (PC 61 BM), enabling significant enhancements in electrical conductivity without compromising film morphology, even at high doping concentrations. The high miscibility and doping efficiency of TMP make it promising for application in organic thermoelectric devices. Moreover, TMP‐doped gNDI‐BT films demonstrate superior performance as source‐drain electrodes in n‐channel N2200 organic transistors, resulting in devices that exhibit dramatically enhanced stability in bias‐stress, operational, and storage conditions compared to conventional metal electrodes. These findings highlight TMP as a transformative n‐dopant, paving the way for the development of high‐performance and stable organic electronic devices.