Improved opto-electronic properties of silicon heterojunction solar cells with SiO_x/Tungsten-doped indium oxide double anti-reflective coatings

Abstract

Amorphous SiOx was prepared by plasma enhanced chemical vapor deposition (PECVD) to form SiOx/tungsten-doped indium oxide (IWO) double anti-reflective coatings for silicon heterojunction (SHJ) solar cell. The sheet resistance of SiOx/IWO stacks decreases due to plasma treatment during deposition process, which means thinner IWO film would be deposited for better optical response. However, the comparisons of three anti-reflective coating (ARC) structures reveal that SiOx film limits carier transport and the path of IWO–SiOx–Ag structure is non-conductive. The decrease of sheet resistance is defined as pseudo conductivity. IWO film capping with SiOx allows observably reduced reflectance and better response in 300–400 and 600–1200 nm wavelength ranges. Compared with IWO single ARC, the average reflection is reduced by 1.65% with 70 nm SiOx/80 nm IWO double anti-reflective coatings (DARCs) in 500–1200 nm wavelength range, leading to growing external quantum efficiency response, short circuit current density (Jsc), and efficiency. After well optimization of SiOx/IWO stacks, an impressive efficiency of 23.08% is obtained with high Jsc and without compromising open circuit voltage (Voc) and fill factor. SiOx/IWO DARCs provide better anti-reflective properties over a broad range of wavelength, showing promising application for SHJ solar cells.

ITO-Free Silicon Heterojunction Solar Cells With ZnO:Al/SiO2 Front Electrodes Reaching a Conversion Efficiency of 23%

“…The ITO cells show better values for Rsh and c than the ZnO:Al samples probably due to the better conductivity and better contacts to both silver and n layer leading to a slightly better FF. Remarkable is the Rsh improve of the ZnO:Al sample after the SiO2 cap deposition which might be attributed to the TCO conductivity variation due to the hydrogen incorporation during the PECVD SiO2 deposition, as seen previously by Yu et al [10].…”

“…Supported by optical simulations, we demonstrate an optical improvement of the SHJ finished cells when introducing an additional plasma-enhanced chemical vapor deposited (PECVD) silicon dioxide (a-SiO2) antireflection (AR) layer on top of the ZnO:Al. This double AR stack concept has been used in the past by other groups using different materials (ITO, IWO as TCO and MgF2 or SiO2 as AR coating) showing also a clear optical improvement due to the double layer [8][9][10][11][12][13][14][15]. However, little or none of this AR benefit will remain in an encapsulated module due to the refractive index of the polymer encapsulation foil having the same value of about 1.5 as the a-SiO2.…”

Electronic structure of indium-tungsten-oxide alloys and their energy band alignment at the heterojunction to crystalline silicon

“…These layers are among the doped indium oxide layers with the highest mobility 11 . Furthermore WO x doped InO x films (1 wt%) have been applied in silicon heterojunction solar cells as double anti reflective coating leading to up to 23 % efficiency 29 .…”

Toward Efficiency Limits of Crystalline Silicon Solar Cells: Recent Progress in High‐Efficiency Silicon Heterojunction Solar Cells

“…In 2019, a number of groups demonstrated that SiN x /TCO composite layers at the front surface for rear-emitter SHJ solar cells can enhance the optical performance without damaging the lateral transport of carriers and the passivation. [93,97,98] In this architecture the parasitic absorption of the TCO can be reduced by designing a thinner TCO layer than the single-layer anti-reflective optimum (≈80 nm). In this case, a second anti-reflecting coating such as SiN has to be deposited on top of the TCO to minimize reflection losses.…”