Efficient Non-Volatile WORM Memory Devices from Ferrocene Functionalized Quinoxaline Systems

The impact of introducing a redox-active system to the molecular framework of an organic small molecule on the resistive switching memory behaviour is studied using a series of novel quinoxaline-ferrocene systems. The quinoxaline acceptor part has been modified with different substitutions, impacting the overall electronic properties and leading to diverse device performances. The devices exemplified appreciable non-volatile WORM memory behaviour with an ON/OFF ratio exceeding 10⁴ and the lowest recorded threshold voltage of -0.69 V with substantially good endurance (100 cycles) and retention (10⁴ s) characteristics. The photophysical studies revealed good intramolecular charge transfer between the ferrocene and quinoxaline units. The electrochemical investigation demonstrated a weak redox activity of the ferrocene unit when attached to strong electron-withdrawing quinoxaline units, resulting in a decrease in the intensity of the reduction peak. Furthermore, an optimum band gap was found for all the compounds, which ranged between 2.74 to 2.97 eV. The resistive switching mechanism was validated by molecular simulations, and charge transfer and charge trapping processes, along with the redox activity of the ferrocene center, contributed to the observed memory behaviour in these devices.