Numerical investigation of vacuum surface flashover triggered by inverted potential gradient on solar cells using particle-in-cell method

Spacecraft electrostatic discharge is a type of surface discharge in vacuum which is commonly known as vacuum surface flashover, posing a significant threat to the safe operation of spacecraft solar cells. This numerical study investigates vacuum surface flashover on spacecraft solar cells triggered by an inverted potential gradient (IPG), using particle-in-cell simulations. Incorporating the realistic solar cell structure [room temperature vulcanized (RTV) adhesive, cover glass, and metal interconnector] and dielectric trap effects on secondary electron emission simulations reveal that field-emitted electrons from the cathode triple junction (CTJ) accelerate in the IPG field, collide with dielectrics, and initiate secondary electron emission avalanches (SEEAs). Key findings show that higher anode voltages intensify flashover by promoting electron multiplication, while lower voltages suppress SEEA through negative charge accumulation at the cathode. Dielectric properties critically regulate discharge through thicker RTV adhesive, reduced glass secondary electron yield, and higher trap density inhibit surface charging and SEEA development. Initial surface charge polarity and distribution also alter the SEEA initiation and development, and it is found that negative initial charges near the CTJ uniquely impede avalanche initiation. A non-uniform charge distribution can alter the propagation direction of secondary electron avalanches. These insights provide mechanistic guidance for flashover mitigation in space applications.