A path towards a better characterisation of silicon thin‐film solar cells: depth profile analysis by pulsed radiofrequency glow discharge optical emission spectrometry

Abstract

The analytical potential of radiofrequency pulsed glow discharge optical emission spectrometry (rf-PGD-OES) is investigated for quantitative depth profiling analysis of thin-film solar cells (TFSC) based on hydrogenated amorphous silicon (a-Si:H). This method does not require sampling at ultra-high-vacuum conditions, and so it facilitates higher sample throughput than do reference techniques. In this paper, the determination of compositional depth profiles of a-Si:H TFSC was performed by resorting to a multi-matrix calibration procedure. For this purpose, certified reference materials, as well as laboratory standards based on individual layers of doped a-Si:H, were simultaneously employed to build the analytical calibration curves. Results show that rf-PGD-OES allows us to discriminate the different layers of photovoltaic devices: the front contact composed by ZnO:Al 2 O 3 (AZO), the a-Si:H layer (the B-doped, intrinsic a-Si:H and P-doped films), the AZO/ Al back contact and substrate. A good agreement with the nominal values for element concentrations (e.g. 0.4% of H, 1.5% of B and 3.7% of P) and layer thicknesses (in the range of 950 nm for the front contact and 13 nm for the P-doped a-Si:H layer) was obtained, demonstrating the ability of rf-PGD-OES for a direct, sensitive and high-depth-resolution analysis of photovoltaic devices. Moreover, diffusion processes between the coating layers, which could have an important influence on the final efficiency of TFSC, can be identified as well. Hence, the findings support the use of rf-PGD-OES as an analysis method in the development of photovoltaic thin films.

Atomic spectrometry update. Review of advances in the analysis of metals, chemicals and functional materials

“…A multi-matrix calibration procedure was adopted involving the use of CRMs without hydrogen and laboratory-prepared standards with hydrogen (doped layers of a-SiH). The GD-OES method 184 provided results in agreement with notional values for B-doped, intrinsic a-SiH, and P-doped layers (1.5%, 0.4% and 3.7% respectively). The OES technique was also able to provide layer thicknesses as low as 13 nm for the P-doped a-Si-H layer and it was suggested that it was possible to identify diffusion processes.…”

“…The sensitivity and accuracy of the technique used to measure doping and trace elements is, therefore, critical. Thus, Sanz-Medel and co-workers investigated the quantitative depth proling of hydrogenated amorphous silicon (a-SiH) used in solar cells using a pulsed rf GD source with both OES 184 and MS 185 detection. A multi-matrix calibration procedure was adopted involving the use of CRMs without hydrogen and laboratory-prepared standards with hydrogen (doped layers of a-SiH).…”

Nanometer‐Scale Depth‐Resolved Atomic Layer Deposited SiO2 Thin Films Analyzed by Glow Discharge Optical Emission Spectroscopy

“…Radio‐frequency glow discharge optical emission spectroscopy (rf‐GDOES) has been applied for diverse thin film analyzes, both on insulating and conducting layers. It has been used for example, for the analysis of PECVD SiO 2 layers, PVD Cu(In,Ga)Se 2 thin film and atomic layer deposition (ALD) ZnO . Most of the work has focused on the elemental concentration profiles and the development of the novel instrumental setups.…”

Rapid quantitative analysis of elemental composition and depth profile of Cu(In,Ga)Se2 thin solar cell film using laser-induced breakdown spectroscopy

“…Whereas depthwise elemental grading is known to be important for high efficiency CIGS solar cell [3], XRF can provide average composition only with a limitation in detecting light trace elements such as Na. Recently, glow discharge optical emission spectroscopy (GD-OES) was introduced as an alternative fast quantitative analysis method (a few tens of second) [4]. However, GD-OES measurement requires a relatively large sample size (a few cm 2 ) for vacuum holding, which is a disadvantage for repetitive measurement for product assessment due to increased loss of cell area.…”