Trace-level oxygen doping in organic semiconductors: mechanistic insights and precise modulations
Organic semiconductors (OSCs) are pivotal for large-area wearable devices, optoelectronic displays, logic circuits, and next-generation optoelectronics, yet their commercialization is impeded by extrinsic impurities, particularly ubiquitous oxygen. Oxygen's high electronegativity drives redox interactions within OSCs, traditionally viewed as detrimental charge-carrier traps that degrade performance and stability. Recent evidence reveals a paradoxical effect: at trace levels, oxygen doping can enhance device performance and stability by pre-emptying donor-like traps. This perspective delineates the mechanistic underpinnings of trace oxygen doping, discussing state-of-the-art modulation strategies to optimize device mobility and stability. Through systematic analysis of structure-property relationships, we examine oxygen-induced modifications in charge transport dynamics and operational reliability. We propose a development framework for oxygen element doping engineering and outline emergent challenges in interfacial stabilization protocols. The analysis synthesizes findings from recent literature, including observations that prolonged air exposure leads to oxygen adsorption and penetration into the organic semiconductor channel, forming traps. By reconciling contradictory roles of oxygen, this work provides a roadmap for precise oxygen modulation, aiming to overcome stability bottlenecks in organic field-effect transistors (OFETs), organic light-emitting diodes (OLEDs), organic photovoltaic cells (OPVs), and sensing devices. The perspective underscores the need for targeted strategies to control oxygen incorporation at trace levels, balancing trap passivation and doping effects to achieve optimized optoelectronic performance and operational longevity.