Influence of the textured pyramid size on the performance of silicon heterojunction solar cell

By adjusting the KOH/H2O texturing condition intendedly, different random pyramidal textures with the average pyramid size of 8 μm (large), 4 μm (medium) and 1.5 μm (small) were prepared on N type M2 monocrystalline silicon substrates for the fabrication of silicon heterojunction (SHJ) solar cell. It was evidenced that the pyramid morphology not only impacted the reflection of incident light and the heterojunction interface passivation quality but also affected the interface contact property between transparent conductive oxide (TCO) layer and Ag electrode. The texture with small pyramids presented the best anti-reflective and passivation performance due to the pyramidal size distribution uniformity, which brought the SHJ solar cell the highest short-circuit current density (JSC) and open-circuit voltage (VOC). However, the texture with small pyramids also led to the worst fill factor (FF). As a result, there was no obvious difference on the conversion efficiency for the textures with different pyramidal size. By characterizing the TCO/Ag contact, the FF reduction induced by the small pyramid texture could be attributed to the increased specific contact resistance of the TCO/Ag contact, which resulted from the fact that there were lots of voids between the TCO layer and Ag electrode, since Ag particles with a larger size than the small pyramids could not fill into the limited space between the adjacent pyramids. As a result, in order to realize the potential to enhance the SHJ solar cell conversion efficiency by adopting the texture with small pyramids, new Ag paste with smaller Ag particles should be adopted.