Unraveling the Proton-Induced Degradation Mechanism in Quantum-Dots Light-Emitting Diode for Space Applications

Semiconductor materials capable of operating in extreme space environments are increasingly important. Colloidal quantum dots (QDs) are widely utilized in optoelectronic applications, but their radiation stability at the device level remains largely unexplored. Here, we investigate the origin of proton-induced degradation in CdSe/ZnS quantum dots light-emitting diodes (QLEDs) with fluences from 10¹³ to 10¹⁵ p/cm². While negligible degradation or slight improvement in diode behavior are observed at low fluence, severe deterioration occurs above 10¹⁴ p/cm², leading to complete luminance loss at 10¹⁵ p/cm². Electrical analysis reveals a substantial increase in trap density, particularly at the QD/ZnO interface. Depth-resolved ToF-SIMS and XPS results indicate that proton irradiation induces detachment of organic ligands such as oleic acid and trioctylphosphine from the ZnS shell. The ligand-depleted ZnS surface is likely to couple electronically with defect-associated states at the ZnO surface through local charge redistribution, generating high-density interfacial trapping states that hinder charge injection into the emissive QD layer. This interfacial degradation accelerates non-radiative recombination and device failure, highlighting the critical need for robust ligand passivation strategies for space applications.