Impact of black silicon on light‐ and elevated temperature‐induced degradation in industrial passivated emitter and rear cells

Abstract

Light and elevated‐temperature induced degradation (LeTID) is currently a severe issue in passivated emitter and rear cells (PERC). In this work, we study the impact of surface texture, especially a black silicon (b‐Si) nanostructure, on LeTID in industrial p‐type mc‐Si PERC. Our results show that during standard LeTID conditions the b‐Si cells with atomic‐layer‐deposited aluminum oxide (AlOx) front surface passivation show no degradation despite the presence of a hydrogen‐rich AlOx/SiNx passivation stack on the rear. Furthermore, b‐Si solar cells passivated with silicon nitride (SiNx) on the front lose only 1.5%rel of their initial power conversion efficiency, while the acidic‐textured equivalents degrade by nearly 4%rel under the same conditions. Correspondingly, clear degradation is visible in the internal quantum efficiency (IQE) of the acidic‐textured cells, especially in the ~850 to 1100‐nm wavelength range confirming that the degradation occurs in the bulk, while the IQE remains nearly unaffected in the b‐Si cells. The observations are supported by spatially resolved photoluminescence (PL) maps, which show a clear contrast in the degradation behavior of b‐Si and acidic‐textured cells, especially in the case of SiNx front surface passivation. The PL maps also suggest that the magnitude of LeTID scales with surface area of the texture, rather than wafer thickness that was recently reported, although the b‐Si cells are slightly thinner (140 vs 165 μm). The results indicate that b‐Si has a positive impact on LeTID, and hence, benefits provided by b‐Si are not limited only to the excellent optical properties, as commonly understood.

Recent Progress of Black Silicon: From Fabrications to Applications

“…In particular, it can be distributed in remote areas, mountains, deserts, islands, and rural areas to save on costly transmission lines. In recent years, black silicon has become one of the materials used to make solar cells [ 72 , 97 , 98 , 99 , 100 , 101 ]. The research hotspot is to change the surface structure of black silicon [ 102 ] and passivate black silicon [ 103 ].…”

Mass Production Test of Solar Cells and Modules Made of 100% UMG Silicon. 20.76% Record Efficiency

“…The combination of B-Si and PDG together with the usage of high-quality silicon purified by metallurgical route, also known as upgraded metallurgical grade silicon (UMG-Si), can contribute to lower production cost of PV ($/kWp). Pasanen et al have also published the positive impact of B-Si on solar cells in terms of Current Induced Degradation, which emphasizes even more the possibilities of UMG-Si [3]. Under an economical assessment, Modanese et al [13] calculated a relative cost reduction of up to 11.7% for a multicrystalline B-Si + PERC solar cell compared with a monocrystalline PERC solar cell, being most of the reduction related to feedstock and ingot growing.…”

Economic Advantages of Dry-Etched Black Silicon in Passivated Emitter Rear Cell (PERC) Photovoltaic Manufacturing

“…Thus, the high performance of the DRIE b-Si successfully etched in lab-scale facilities [45] is not expected to hinder in any way a successful upscaling to full industrial PV lines, and its costs are already included in the mid-and worst-case scenarios (Figure 4). Furthermore, the added benefits of b-Si etched by RIE of mitigating the light-induced degradation [28] and of allowing a much wider angle of acceptance [45] in industrial mc-Si PERC cells confirm that the cell efficiencies considered in this work (22%) are feasible within a reasonably short amount of time necessary for industrial process optimization.…”

“…A relatively new approach to improving solar cells efficiencies further is to shift to nanostructured silicon (so called 'black-Si', b-Si), which has been shown to effectively decrease reflective losses in diamond-sawn mc-Si wafers [25,26], enhance metal gettering [27], and prevent cell power conversion efficiency degradation under light exposure [28]. In addition, black-Si has been shown to decrease reflectance by more than twofold compared to conventional texturized surfaces, for angles of incident light up to 60 • [29].…”