Spray-coated SiO2/PECVD SiNx stack for the passivation of n+ emitter of p-type Si solar cell

Inefficient passivation of phosphorous diffused emitter is one of the limiting factors contributing to lower efficiency in advanced p-type silicon solar cells. Stack of SiO2 and SiNx with the former as an intermediate layer beneath SiNx provides better emitter passivation in comparison to SiNx film alone. Thermal oxide is reported to provide the best passivation, but it is not industrially viable. We demonstrate spray SiO2/SiNx as a viable alternative to thermal SiO2/SiNx stack. A few nanometer thin (∼6.1 nm) spray SiO2 film was first time demonstrated on micrometer sized textured pyramid with full coverage over an entire deposited area. The passivation of symmetrical (n+-p-n+) structure shows iVoc ∼660 mV and passivation uniformity over the entire wafer area for both the stacks. Voc ∼630 mV is achieved on cells with spray and thermal SiO2 as a passivating layer. Similar front passivation is further verified by overlapping IQE in the shorter wavelength range. Therefore, incorporating SiO2 film deposited via an industrially viable spray-coating process as a passivating layer at the front provides overall cell performance similar to the thermally grown SiO2.