Photovoltaics (PV)
Depth Profile Analysis of PV cells by RF GD

Depth Profile Analysis of PV cells by RF GD
Legend: Analysis of a PV solar cell by RF GD-OES

Glow Discharge Instruments rely on the controlled erosion of representative part of a material (2 or 4mm) by a high density (1014/cm3) and low energy RF plasma and provides the elemental distribution as a function of the penetration depth.

When coupled to a high resolution optical system, the resulting technique is called RF GDOES and is well established in the PV domain, when coupled to more sensitive TOF MS detection, it is named Plasma Profiling Time of Flight Mass Spectrometry. Results have been published on thin films cells (CIGS), Si cells and hybrid ones.

Both instruments feature an advanced pulsed RF source allowing the measurements of conductive and non conductive layers without any unwanted diffusion of the species during the GD operation - the TOFMS offering the additional advantage of isotopic depth profiling.

Ultra Fast Techniques (2-3 minutes are needed to profile a complete cell and reach the glass substrate) they nevertheless offer excellent depth resolution down to the nanometre depending on the roughness of the cells and are therefore ideal to detect compositional changes, gradients and interface contaminations.

The capability to simultaneously measure all elements of interest (Na, H, O, Ca, C, Zn, Cd, Te, Cu, In, Ga, Se, Mo, Sn, Al etc – and even compounds in the case of TOFMS detection) and the speed of analysis allow quick check up of each stage of the evaporation, deposition or annealing processes permitting to quickly react to observed variations.   

The unique characteristics of the RF GD plasma have also been used with great benefits to clean cross sections of PV cells before SEM observation or to reach embedded interfaces below encapsulation.

Reading: F. Oliva & al, “Formation Mechanisms of Cu(In,Ga)Se2 Solar Cells Prepared from Electrodeposited Precursors” Thin Solid Films doi: 10.1016/j.tsf.2012.11.106

Contact us to see what RF GD could do for your samples.