A route towards high-efficiency silicon heterojunction solar cells

In this work, we propose a route to achieve a certified efficiency of up to 24.51% for silicon heterojunction (SHJ) solar cell on a full-size n-type M2 monocrystalline-silicon Cz wafer (total area, 244.53 cm(2)) by mainly improving the design of the hydrogenated intrinsic amorphous silicon (a-Si:H) on the rear side of the solar cell and the back reflector. A dense second intrinsic a-Si:H layer with an optimized thickness can improve the vertical carrier transport, resulting in an improved fill factor (FF). In order to reduce the plasmonic absorption at the back reflector, a low-refractive-index magnesium fluoride (MgF2) is deposited before the Ag layer; this leads to an improved gain of short circuit current density (J(sc)). In total, together with MgF2 double antireflection coating and other fine optimizations during cell fabrication process, similar to 1% absolute efficiency enhancement is finally obtained. A detailed loss analysis based on Quokka3 simulation is presented to confirm the design principles, which also gives an outlook of how to improve the efficiency further.