Cu(InGa)Se₂ solar cells on a flexible polymer web

Abstract

CuInGaSe 2 films on 6-inch wide Mo coated polyimide web substrate in a roll-to-roll vapor deposition system from elemental sources is described. Material transport from the sources to the moving web substrate has been modeled by combining an evaporative effusion model and the gas flow kinetics and by experimentally determining the flux intensity profile. The model gives a reasonably good approximation of the Ga profile in the films. Poor adhesion of the selenide film to molybdenum has been resolved by depositing a thin layer of b-(Ga 0Á8 In 0Á2 ) 2 Se 3 precursor layer. Two-dimensional compositional mapping by energy dispersive spectroscopy of 5feet-long web gave 0Á88 AE 1Á9% and 0Á28 AE 2Á5% respectively for Cu/(Ga þ In) and Ga/(Ga þ In) ratios, indicating highly uniform film composition. This compositional uniformity translated to the uniformity in the devices fabricated on the web. The open-circuit voltages of the devices from the centerline of the 5-feet web were measured to be 0Á529 AE 0Á86%. A two-dimensional device efficiency survey gave 9Á2 AE 1%. The process was able to produce high-quality material, as defined by the best device efficiency, for a wide range of Cu/(Ga þ In) ratios. The best efficiency achieved so far was 12Á1% with MgF 2 anti-reflection coating.

Pathways to improved performance and processing of CdTe and CuInSe<inf>2</inf> based modules

“…The challenge with elemental multi-source evaporation is the high source temperatures required to obtain high film growth rates coupled with the Se environment [21). This is particularly true for the Cu source which operates at -1600 o C. Also, in in-line processing, where the substrate or web moves over a sequential array Cu, Ga, and In source, there is an inherent through film non-uniform Ga and In distribution incorporated in the film [22,23). Design and control of the system, particularly when depositing on a continuous web requires in situ process control and diagnostics [24] that have been implemented by several companies.…”

Design Strategy for Scale-Up of Physical Vapor Deposition of Cu(InGa) Se2 on Flexible Substrates

“…The particular manufacturing technique adopted at the University of Delaware's Institute of Energy Conversion (IEC) is the PVD of Cu(InGa)Se2 thin-films onto a 6-inch flexible polyimide substrate using a roll-to-roll processing scheme [4]. The film is deposited from a series of linear elemental sources located sequentially in a vacuum chamber.…”

Development of a Low Cost Insulated Foil Substrate for Cu(InGaSe)2 Photovoltaics

“…In this case, in addition to the device performances, the composition of the absorbers has been measured (Table IV). It should be pointed out that Cu(InGa)Se 2 films deposited in the stationary system have uniform depth composition while the ones deposited in the in-line system always show a gradient in Ga and In through the depth (3,4,6) . As such compositions measured by energy More precise characterization of the chemistry and of the interdiffusion of trace amounts of impurities from SLG and SS/SBR substrates were characterized by the secondary ion mass spectroscopy (SIMS) at NREL.…”

“…Initially the NaF evaporation from a powdered source was evaluated in a bell-jar vacuum system. Using the vapor pressure data from literature (5) and the film deposition modeling previously developed in our laboratories (6) the amount of NaF impinging on the substrate was estimated as shown in Figure 11. The red line in the figure gives the amount of Cu impinging at the same location.…”