Achievement of 25.54% power conversion efficiency by optimization of current losses at the front side of silicon heterojunction solar cells

Abstract

Parasitic absorption in the front window layers of transparent conductive oxide (TCO) films and carrier selective collection layers and the optical shading losses from the metallic finger grid mainly limit the current generation in silicon heterojunction (SHJ) solar cells. In this work, we demonstrate an improved short-circuit current density (J sc ) of 40.24 mA/cm 2 through a combination of novel window layers composed of transition metal doped indium oxide (IMO) and hydrogenated nanocrystalline silicon oxide (nc-SiO x :H) films and Cu plating for SHJ solar cells. By introducing water vapor during direct current (DC) magnetron sputtering deposition process, IMO films show a large optical band gap (E g ) of about 3.88 eV and high mobility up to 83.2 cm 2 /VÁs, while maintaining a low carrier concentration, which leads to high transparency and low near-infrared (NIR) free carrier absorption (FCA). In addition to its high deposition rate and crystalline volume fraction, we found that nc-SiO x :H films deposited by very high frequency (VHF) excited plasma-enhanced chemical vapor deposition (PECVD) show an excellent surface passivation quality, which not only improves the open circuit voltage (V oc ) of SHJ cells but also increases the J sc through improved carrier selective collection. The quantified J sc breakdown analysis was performed to identify the room for improvement, and it showed that the front shading loss (about 1.32 mA/cm 2 ) is the largest portion. By combining the benefits of these window layer enhancements with the further use of fine line width and conductivity of Cu plating, SHJ solar cells, with a J sc improvement of 0.57 mA/cm 2 and a certified efficiency of 25.54%, were achieved on a total area of 274.5 cm 2 using in-house pilot production line equipment.

Buried‐Interface Engineering of Conformal 2D/3D Perovskite Heterojunction for Efficient Perovskite/Silicon Tandem Solar Cells on Industrially Textured Silicon

“…Transparent conductive oxide (TCO) films were prepared by co-sputtering of ITO (In 2 O 3 :SnO 2 = 97:3 wt%) and indium oxide doped with transition metal (IMO). [63] Tandem Solar Cell Fabrication: Before the fabrication of perovskite top cells, 15 nm ITO was sputtered on the front side as the recombination junction. Next, the perovskite top cells were fabricated using a similar hybrid two-step sequential method as the single-junction device except for the top electrode.…”

“…Transparent conductive oxide (TCO) films were prepared by co‐sputtering of ITO (In 2 O 3 :SnO 2 = 97:3 wt%) and indium oxide doped with transition metal (IMO). [ 63 ]…”

Multifunctional Titanium Oxide Layers in Silicon Heterojunction Solar Cells Formed via Selective Anodization

“…Strategies must be found to reduce or replace these elements so that the SHJ technology can increase its share in the photovoltaic market, which will soon grow into the terawatt range of annual production. [1] Regarding silver reduction, several copper electroplating approaches were evaluated in the last decade, [2,3] for example, using an organic resist masking as published by Maxwell/Sundrive [4] or Centre Suisse d'Electronique et de Microtechnique. [5] Another option is the NOBLE (native oxide barrier layer for selective electroplating) process sequence, [6] developed at Fraunhofer ISE, which allows to replace silver screen printing by copper electroplating without using costly organic masking, as shown in Figure 1a.…”

Atomic Force Microscopy Analysis of Aluminum Layer Properties and Correlation to Masking Functionality in Copper Plating Metallization for Solar Cells

“…As summarized in the review articles, several institutes and companies such as Kaneka, CSEM, INES, GS Solar, Hevel, and Sundrive (reduced ITO as seed instead of PVD layer) have reached remarkable cell performance with this approach, lately above 26% conversion efficiency on industrial size SHJ solar cells. [16,18,20,21] However, it seems that the use of a thick organic mask (e.g., photoresist), which produces waste water polluted with organics, is not considered viable for mass production in the PV industry.…”