Lift-off process reducing crack formation and its Cu(In,Ga)Se2 thin film solar cell applications

Origin of Crossover in Current Density–Voltage Characteristics of Cu(In,Ga)Se2 Thin Film Solar Cell Fabricated Using Lift-Off Process

“…Our lift-off solar cell achieves the highest conversion efficiency compared with previous reports of CIGS lift-off solar cells. [5][6][7]9) The conversion efficiency of this lift-off solar cell is, however, still lower than that of the standard cell from Table I. On the other hand, the crossover is observed between the photo and dark J-V characteristics for only the lift-off solar cell from Figs.…”

“…6) Since solar cell performance is generally characterized by current density-voltage (J-V ) measurements [air mass (AM) 1.5G, 100 mW/cm 2 , 25 C], correct interpretation of J-V characteristics is required to improve the conversion efficiency. In fact although the J-V characteristics of the lift-off solar cell show a particular shape, such as the crossover phenomenon, 7) the cause of this has not been clarified yet. In this study, we focus on the behavior of the photocurrent of the lift-off solar cell to interpret these J-V characteristics.…”

“…The solar cells were fabricated using the lift-off process as follows. 7) First, a 0.8-m-thick Mo layer was deposited on an SLG substrate without intentional substrate heating by the RF magnetron sputtering method. Then, a 2.5-m-thick CIGS layer was deposited on a Mo/SLG substrate by a three-stage evaporation process at the highest substrate temperature of approximately 550 C. 8) After CIGS surface cleaning by a KCN solution, 0.2-m-thick Au/1.6-m-thick Mo stacked layers were deposited as a back electrode.…”

“…Then, a 2.5-m-thick CIGS layer was deposited on a Mo/SLG substrate by a three-stage evaporation process at the highest substrate temperature of approximately 550 C. 8) After CIGS surface cleaning by a KCN solution, 0.2-m-thick Au/1.6-m-thick Mo stacked layers were deposited as a back electrode. 7) After the samples were annealed at 250 C for 30 min in nitrogen ambient, an alternative SLG substrate was bonded onto the Mo/Au/CIGS/Mo/SLG structure with conductive epoxy glue. Then, alternative-SLG/epoxy/Mo/Au/CIGS stacked layers were detached from the primary Mo/SLG substrate by applying tensile strain.…”

Effect of rear-surface buffer layer on performance of lift-off Cu(In,Ga)Se2 solar cells

“…8) To avoid this problem, the lift-off process has been developed. [9][10][11][12][13][14] This process allows absorber layers to be separated from primary substrates using a sacrificial layer and subsequent transfer onto an alternative substrate. In CIGS solar cells, a sacrificial layer is a MoSe 2 thin layer formed between CIGS and Mo.…”