Investigation of High Nitrogen Composition $\text{SiN}_{\mathrm{x}}$ for Textured Front Surface Passivation of n-Type Silicon Solar Cells in Terms of Light Stability of Injected Negative Charge and Cell Performance

In this paper, we explored the potential of passivating the B-doped emitter with ${SiN}_{{x}}$ film(s) with an externally injected negative charge by using our plasma charge injection technology to replace the more costly Al 2 O 3 passivation technology, by addressing some issues and challenges in the light stability for light exposure. At first, we investigated the stability of injected negative charge and passivation quality of single layer ${SiN}_{{x}}$ films with low and ${high}-{x} {x}\sim {1.01}$ and 1.30) as well as ${dual}-{x} ({x}\sim {1.30}/{1.01})\ {SiN}_{{x}}$ films on B doped emitter. About $-{1}{E}{13}\ {cm}^{-{2}}$ negative charge was injected into single- and ${dual}-{x}\ {SiN}_{{x}}$ layers by a plasma charge injection system. It was found that a single ${SiN}_{{x}}$ film with ${x}\sim {1.01}$ could not hold injected negative charges after several hours of exposure to simulated visible sunlight. However, excellent charge stability was confirmed in an 80 nm thick single ${SiN}_{{x}}$ layer with high ${x}\sim {1.30}$ , which was able to retain more than $\sim {2}{E}{12}\ \ {cm}^{-{2}}$ negative charge density after the extrapolated 50K hours $(\sim {25}$ years) exposure to sunlight. For the ${dual}-{x}\ {SiN}_{{x}}$ stacks with a total thickness of $\sim {80}\ {nm}$ , the charge stability got even better with the increasing thickness of the ${high}-{x} {SiN}_{{x}}$ . In parallel, we investigated the passivation quality of the single layer ${SiN}_{{x}}$ and dual-x ${SiN}_{{x}}$ stacks on the B emitter before charge injection. The uncharged ${low}-{x}$ single ${SiN}_{{x}}$ layer showed very good passivation both before and after metallization with ${iV}_{{oc}}\sim {680}{mV}$ . However, the uncharged single layer ${SiN}_{{x}}$ with high-x showed inferior passivation quality before metallization and significant degradation after metallization with ${iV}_{{oc}}\sim {590}{mV}$ . In contrast, the ${dual}-{x}\ {SiN}_{{x}}$ stacks showed comparable passivation quality to the single layer ${low}-{x} {SiN}_{{x}}\ ({x}\sim {1.01})$ . Passivation properties of the charged ${SiN}_{{x}}$ films are being studied now and will be reported in the paper with cell performance.