Nanosecond laser scribing of CIGS thin film solar cell based on ITO bottom contact

Abstract

Cu(In,Ga)Se2 (CIGS) thin films, a promising photovoltaic architecture, have mainly relied on Molybdenum for the bottom contact. However, the opaque nature of Molybdenum (Mo) poses limitations in module level fabrication by laser scribing as a preferred method for interconnect. We examined the P1, P2, and P3 laser scribing processes on CIGS photovoltaic architecture on the indium tin oxide (ITO) bottom contact with a cost-effective nanosecond pulsed laser of 532 nm wavelength. Laser illuminated from the substrate side, enabled by the transparent bottom contact, facilitated selective laser energy deposition onto relevant interfaces towards high-quality scribing. Parametric tuning procedures are described in conjunction with experimental and numerical investigation of relevant mechanisms, and preliminary mini-module fabrication results are also presented.

Effect of Nanosecond Laser Beam Shaping on Cu(In,Ga)Se2 Thin Film Solar Cell Scribing

“…However, we proceed with a fixed ITO film thickness of ∼200 nm as a harsh condition in a fundamental sense and also for the practical purpose of keeping material cost low. Although the current study is devoted to P2 laser scribing, the results can be effectively applied to the P3 laser scribing process as very similar scribing width and threshold were confirmed in the previous works by authors because laser-induced temperature and stress profiles are not affected much by the existence of an additional top contact (AZO; Al-doped zinc oxide) when a nanosecond laser beam of 532 nm wavelength is illuminated from the SLG substrate side …”

“…Then, CIGS absorber layer of ∼2 μm thickness was first deposited on ITO by the coevaporator method, followed by deposition of CdS and i-ZnO (∼60 nm thick CdS by dip coating, ∼50 nm thick i-ZnO by sputtering). As authors previously reported, use of a thicker ITO film (∼400 nm) could efficiently suppress the ITO damage via a heat spreading effect during the P2 laser scribing process. However, we proceed with a fixed ITO film thickness of ∼200 nm as a harsh condition in a fundamental sense and also for the practical purpose of keeping material cost low.…”

“…In earlier stage, the architecture of TCO bottom contacts has been tested for CIGS thin film PV mainly at the cell level, , and indium tin oxide (ITO) has been accepted as a promising TCO to this end, allowing ohmic contact with CIGS . Recently, the authors demonstrated all the P1, P2, and P3 laser scribing processes to fabricate a mini-module on the thin film CIGS architecture with an ITO bottom contact, using a cost-effective nanosecond laser beam illuminated from the transparent glass substrate side . In subsequent efforts, we have attempted to reduce the P2 and P3 scribing widths, i.e.…”

Laser Processing Methods for Perovskite Solar Cells and Modules

“…have reviewed the use of lasers for the manufacturing of chalcogenide PV thin film PV modules. [ 9 ] Lasers have become the technology of choice for the production thin film based PV modules including: CIGS [ 10,11 ] a‐Si, [ 12 ] and organic photovoltaics. [ 13 ] The combined advantages of very high process speed, reliability, precision, fine geometries, and the relative cleanliness of the process being the basis for the choice of lasers in automated production lines.…”

“…[7] The history of the use of lasers in semiconductor thin film photovoltaics including scribing, film treatments, performance diagnostics, and thin film characterization from 1986 to 2010 was reviewed by Bartlome et al [8] Simonds et al have reviewed the use of lasers for the manufacturing of chalcogenide PV thin film PV modules. [9] Lasers have become the technology of choice for the production thin film based PV modules including: CIGS [10,11] a-Si, [12] and organic photovoltaics. [13] The combined advantages of very high process speed, reliability, precision, fine geometries, and the relative cleanliness of the process being the basis for the choice of lasers in automated production lines.…”