Investigation of co-evaporated polycrystalline Cu(In,Ga)S₂thin film yielding 16.0 % efficiency solar cell

Abstract

The interest for pure sulfide Cu(In,Ga)S2 chalcopyrite thin films is increasing again because their optical properties make them relevant candidates to be applied as top cell absorbers in tandem structures. Nonetheless, their use as so is still hindered by the level of single-junction cells performance achieved so far, which are far below those demonstrated by selenide absorbers. Amongst the reasons at the origin of the limited efficiency of Cu(In,Ga)S2-based solar devices, one can mention the poor tolerance of S-chalcopyrite to Cu deficiency. In fact, Cu-poor Cu(In,Ga)S2 films contain CuIn5S8 thiospinel secondary phase which is harmful for device performance. In the present work, we investigate Cu(In,Ga)S2 thin films grown by a modified three-stage process making use of graded indium and gallium fluxes during the first stage. The resulting absorbers are single phase and made of large grains extended throughout the entire film thickness. We propose that such a morphology is a proof of the recrystallization of the entire film during the synthesis. Devices prepared from those films and buffered with bath deposited CdS demonstrate outstanding efficiency of 16.0%. Replacing CdS by Zn(O,S) buffer layer leads to increased open circuit voltage and short circuit current; however, performance become limited by lowered fill factor.

Mechanism analysis of CuInS2 and Cu(In,Ga)S2 growth via KCN- and H2S-free process and solar-cell application

“…The [Ga]/([Ga] + [In]) ratio was adjusted to 0.21, which are close to that of the highlyefficient cells achieved in past studies. 26) Figure 1 depicts the schematic diagram for the sulfurization process utilizing the solid phase S source. The Cu-In(-Ga) precursors on Mo-coated SLG and S powder with a weight of 100 mg were set into a graphite box and were sulfurized with an IR gold imagefurnace.…”

Improvement of hetero-interface engineering by partial substitution of Zn in Cu2ZnSnS4-based solar cells

“…CIGSSe-based alloy technologies have reached efficiency levels of 23.35%, which is higher than CdTe and a-Si [2,3]. However, the efficiency of pure sulfide CIGS is 16% as presented recently by Barreau et al for a bandgap close to 1.6 eV [4]. The success of CIGS technology still depends on the availability of indium as a key element in the CIGS production line.…”

Characterisation of the interplay between microstructure and opto-electronic properties of Cu(In,Ga)S2 solar cells by using correlative CL-EBSD measurements

“…The electronic properties and excellent stability make wide gap chalcopyrite interesting for application as the top cell in Si-based tandem solar cells. Sulphide chalcopyrite, Cu(In,Ga)S 2 (CIGS), with a bandgap suitable for top cells in tandem applications has achieved efficiencies above 15% [4,5], whereas the low bandgap selenide, Cu(In,Ga)Se 2 (CIGSe), Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.…”