Lift-Off Process for Flexible Cu(In,Ga)Se₂ Solar Cells

Abstract

A lift-off process for flexible Cu(In,Ga)Se2 (CIGS) solar cells was developed. After the growth of a CIGS thin film on a Mo/glass substrate at 550 °C, the CIGS film was transferred to polyimide and poly(tetrafluoroethylene) films. Process temperatures for the device fabrication after the transfer were less than 100 °C. The conversion efficiencies of the lift-off CIGS solar cells were similar and were almost one-half that of a CIGS solar cell prepared by a standard process. The difference was mainly due to the low fill factor caused by a poor back-contact property and the low short-circuit current caused by an inappropriate band gap profile in the CIGS layer. There still remain problems related to the improvement in efficiency; however, this is the first report on flexible CIGS solar cells on a low-thermal-tolerance substrate. We demonstrated the possibility of freedom of substrate material choice in CIGS solar cells.

Thermomechanical Lift-Off and Recontacting of CdTe Solar Cells

“…The decrease in J sc observed here is a drastic improvement from our previous work in which J sc dropped by almost 50% following lift-off due to device cracking . Similar decreases in performance due to device cracking have also been identified in the early work (2010) of the Minemoto group . In more recent work (2018), they have been able to largely eliminate this issue and achieve similar results of 10.2% lifted off CIGS .…”

Photonic Lift-off Process to Fabricate Ultrathin Flexible Solar Cells

“…Overall, these results demonstrate that the PLO process can aid in fabricating lightweight, ultrathin (<20 μm) solar cells that could be attractive for space and stratospheric applications. Further, this process, as demonstrated, also enables monolithic device fabrication on the top of polymeric films, not requiring transferring the completed devices to foreign substrates after lift-off, which is a typical step in other lift-off mechanisms. − …”

“…In a lift-off process, active device structures are fabricated on a rigid carrier substrate and then removed using either physical, chemical, or thermal methods. Physical methods of cleavage rely on the exertion of significant mechanical forces, which can crack the devices and make achieving process uniformity a challenge. − Chemically aided lift-off involves the dissolution of sacrificial layers between the device and the substrate, often relying on corrosive etchants that can damage device components. − This demands new materials and device designs to avoid a loss of essential device function. Lift-off methods using localized heating with a laser have become attractive .…”

A facile chemical-mechanical polishing lift-off transfer process toward large scale Cu(In,Ga)Se2thin-film solar cells on arbitrary substrates

“…For CIGS-based devices, mechanical lift-off utilizing various adhesive coated transfer substrates has been demonstrated, although crack formation during the lift-off process still poses numerous issues. 17,18 A GaSe release layer between the interface of the Mo/CIGS has been developed making the detachment of the CIGS film easier while decreasing the crack formation density, 19 whilst Tiwari et al have demonstrated a transfer method that utilises a sacrificial NaCl layer for removal of the polymer substrate CIGS solar cells fabricated on glass. Although the device performance demonstrated is good, the use of a polymer substrate with a glass transition temperature of 400 °C poses limitations of the selenization temperature that can be applied.…”