Towards ultrathin copper indium gallium diselenide solar cells: proof of concept study by chemical etching and gold back contact engineering

Abstract

An innovative approach combining chemical etching and a “lift‐off” process, which allows back contact processing after CIGSe deposition, permitted to use Au as a highly reflective back contact in ultrathin CIGSe solar cells. The Au back contact does not degrade the other parameters of the cell, as good ohmicity on CIGSe is achieved. An important photocurrent increase compared with regular Mo back contact solar cells is achieved by the enhanced light trapping effect due to the back reflector, leading to an absolute efficiency increase of +2.5% for a CIGSe thickness of 0.4 µm. This approach could be used for further investigations in improving the back side of ultrathin CIGSe solar cells. Copyright © 2012 John Wiley & Sons, Ltd.

Passivation of Interfaces in Thin Film Solar Cells: Understanding the Effects of a Nanostructured Rear Point Contact Layer

“…Only the light absorbed in the CIGS (termed useful absorption) leads to significant photocurrent. [57,58] These optical losses account for the difference shown in Figure 4b between the light absorption of the CIGS layer and that in the complete solar cell stack. [57,58] These optical losses account for the difference shown in Figure 4b between the light absorption of the CIGS layer and that in the complete solar cell stack.…”

Ultra-thin Cu2ZnSnS4 solar cell by pulsed laser deposition

“…Assuming a series resistance of 1 Ω cm 2 (grey dashed curve), the fill factor and efficiency increase to 58% and 6.3%, respectively. times referred to as "ultra-thin" in the literature [36,37]. In general, if the material properties of the absorber were independent of thickness, one would expect only the short circuit current to be reduced in an ultra-thin absorber, due to 1) incomplete light absorption, and 2) lower collection efficiency, as more minority carriers are generated near the back contact where they can recombine.…”

Light absorption enhancement for ultra-thin Cu(In1−xGax)Se2 solar cells using closely packed 2-D SiO2 nanosphere arrays

“…Therefore, light absorption enhancement is crucial to maintaining high efficiencies for ultra-thin (absorber thickness below to 500 nm) CIGSe solar cells. Previously, light absorption enhancement for CIGSe solar cells was achieved by coating an anti-reflection layer of MgF 2 [4,5] or by improving the internal reflection at the CIGSe/Mo interface via inserting a dielectric layer [6] or via transferring the cells from the typical Mo back contact onto Au which has a better reflectivity [7]. Recently, a number of innovative nanoscale lighttrapping structures have shown the potential to better improve the light absorption including plasmonic structures [8][9][10][11], dielectric diffractive nanostructures [12,13] and photonic crystals [14,15].…”