Thin film solar cells technology based on hydrogenated amorphous silicon (a-Si:H) has undergone a great expansion during recent years. Pulsed radiofrequency glow discharge time-of-flight mass spectrometry (rf-PGD-ToFMS) is able to perform depth profiling analysis of coated materials, providing an excellent tool for rapid and high sensitive chemical characterisation of photovoltaic devices. The hydrogen concentration on a-Si:H thin films is around 10%, which represents a challenge for quantitative depth profile analyses by using GD sources due to the so-called ''hydrogen effect''. It is well-known that when hydrogen is present in the Ar discharge, even in small quantities, significant changes can occur in the ion signal intensities and sputtering rates measured. Therefore, a critical comparison has been carried out by rf-PGD-ToFMS in terms of pulse profiles, spectral interferences and depth resolution for two modes of hydrogen introduction in the discharge, exogenous hydrogen in molecular gaseous form (using the mixture 0.2% H 2 + Ar as discharge gas) or endogenous hydrogen, sputtered as a sample constituent. For this purpose, non-hydrogenated materials (containing B, P and Si) and three types of a-Si:H thin films were investigated. Exogenous hydrogen was found to produce a noteworthy influence on the pulse profiles of the analytes, whereas the effect of the hydrogen sputtered from the samples could be considered less notorious. Moreover, the proper selection of the after-peak region was found to be critical to obtain optimum mass spectra (i.e. high analyte sensitivities free of interferences).

No abstract

No abstract

No 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.