Enhanced Mechanical Stability of CIGS Solar Module with Glass/Polyimide/Indium Tin Oxide for Potentially Flexible Applications

Abstract

Cu(In,Ga)Se 2 (CIGS) is a promising candidate for flexible photovoltaics because of its outstanding efficiency and flexibility. Despite its advantages, achieving high-efficiency CIGS solar cells on a flexible polyimide (PI) substrate is challenging as it requires a low-temperature process and relaxation of the thermal expansion. This limitation is critical in CIGS modules, particularly for monolithic interconnection processes by laser scribing. Furthermore, Mo back-contact (BC)-based PI cells are sensitive to each laser processing step. Laser scribing is one of the important processes in thin-film module manufacturing. In this study, for the first time, we applied indium tin oxide (ITO) instead of Mo as a BC layer on the spin-coated PI on soda-lime glass to obtain mechanically durable CIGS modules. The ITO BC-based module not only provides a crack-free CIGS layer but also offers superior device performance owing to the excellent laser scribing quality. Additionally, electrical properties related to respective scribing steps are analyzed in correlation with observed morphologies to evaluate parasitic resistance and optimize the laser scribing conditions. Consequently, a CIGS monolithic-integrated module with 15.03% efficiency at 40.14 cm 2 (16.3% at 0.480 cm 2 ) is fabricated on a novel "soda-lime glass/coated-PI/ITO structure". We propose ITO BC-based cells as promising candidates for achieving highefficiency and flexible CIGS solar modules.

Performance Improvement of Hybrid-Perovskite Solar Cells with Double Active Layer Design Using Extensive Simulation

“…ZnO and Spiro-OMeTAD are selected as the ETL and the HTL, respectively, from the earlier works, which resulted in obtaining higher efficiency. The front contact electrode, i.e., ITO is used in CIGS-based SCs, and hence, it validates the feasibility of ITO with CIGS materials. − The working principle of SC (CIGS/CsSnI 3 ) is represented in Figure b. The absorption coefficient (α) is illustrated from SCAPS-1D software where we utilized the term α = A α ( h ν – E g ) 1/2 .…”

Laser Scribing for Perovskite Solar Modules of Long‐Term Stability

“…Under high-power and high-overlap conditions, substantial FF loss and 75% increase in dead zone were observed in CIGS solar cells. [39] Thus, it is important to minimize the P3-scribing width as part of the dead zone. A two-step P3-scribing mechanism is used for a single laser shot, which is schematically depicted in Figure 2a.…”

“…[47,48] Figure 2b schematically summarizes the possible issues involved with the single-shot P3-scribing process. Figure 2b shows that 1) the Au electrode delamination near the scribing edge depends on the adhesion of the Au electrode with the underlying layers as a source of the increased dead zone; 2) the diode is damaged by the laser-induced heating damage caused to the nip junction; [39,49] and 3) intermetallic diffusion between laser-heated layers and/or reactions with the ambient air environment (e.g., oxidation-induced material decomposition). A higher laser power (i.e., higher pulse energy) results in a larger scribing size laterally, and an increased scribing depth (removing more thickness/layers) is required for the given laser beam size (see Figure 2c).…”

“…[31] Note that previously we investigated laser scribing using a similar approach not only for perovskites but also for CIGS. [39] For P2 scribing, excessive overlap led to damage in the bottom electrode of the lower layer and the flexible substrate. If the overlap is too small, material removal is not properly achieved, so low-overlap conditions within an appropriate range are suitable for P2 scribing.…”

Roll‐to‐Roll Patterning of Indium‐Tin‐Oxide Electrodes Using a Low‐Cost Laser‐Marking Machine

“…Researchers have long been studying ITO electrode patterning using infrared lasers owing to their ease in patterning. [ 17–19 ] Our research team investigated a cost‐effective method for patterning ITO on flexible substrates and attempted to pattern ITO electrodes using a 3D printer‐based laser. Although the process works at a suitable speed when directly forming an electrode of materials such as copper, etching with a laser to create electrode patterns necessitates multiple scans, requiring a faster laser‐scanning machine than that based on a 3D printer.…”