Comparative secondary ion mass spectroscopy analysis of solar cell structures grown by pulsed laser ablation and ion sputtering

Abstract

We performed a complex secondary ion mass spectroscopy (SIMS) 3D analysis of solar cell structures based on II-VI semiconductors. The chemical composition analysis, as well as the depth distribution of the main elements and contamination were done for AuCu/CdTe/CdS/conducting glass structures. A structure where the II-VI compounds were grown by pulsed laser ablation (PLA) was compared with another structure grown by ion sputtering deposition (ISD). In both cases contamination due to O, C and H was found at high concentrations, particularly at the boundaries between crystallites. In addition to the SIMS depth profiling, the surface roughness (SR) was analysed by atomic force microscopy (AFM). Poor SIMS depth resolution was correlated to high surface roughness. The root-mean-square of the surface roughness (R rms ) was found to be higher for ISD than for PLA structures. In addition, the lateral distribution of the main components and contamination were observed in the microscope mode with a resolution of about 1 µm. A larger lateral contamination was correlated to a larger R rms of the analysed surface. Experimental 'diffusion' tails of Cu and Au from the ohmic contacts on the CdTe layer are also explained by a high R rms for this layer.

CdTe solar cell degradation studies with the use of CdS as the window material

“…The best efficiencies are obtained for the devices with CdS obtained from bath with S/Cd ratio 5:1 and [10], probably as a consequence of the formation of oxide in the metallic back contacts, such as copper, and tellurium oxide, or cadmium tellurate. In our preliminary SIMS studies we have found that oxygen diffuses at high concentrations to the CdTe and CdS layers of solar cells processed by sputtering and laser ablation techniques [11], thus at longer periods of time certainly the PV operations will be affected. Moreover, the photochemical reactions between the gas pollutants in the Mexico City (O 3 , CO, NO 2 , SO 2 , Pb and the suspended particles) and the materials of the solar cells exposed at outdoor conditions can produce oxidation and deterioration of the metal contacts and semiconductors in the solar cell, for example SO, CdO, TeO and CuO.…”

Effect of CdCl2 activation on the impurity distribution in CdTe/CdS solar cell structures

“…More recently, Godines at al. [15] reported a quantitative SIMS investigation of CdTe/CdS/SnO 2 :F structures grown by pulsed laser ablation and ion sputtering deposition. This study used either HgCdTe relative sensitivity factors (RSFs) or a model for the quantification of the results, and was limited to light element impurities such as H, C and O-these were mainly introduced by adsorption from the residual gas atmosphere during the growth.…”

SIMS depth profiling analysis of halogens in CdTe/CdS/TSO solar cells using Cs2M+ cluster ions

“…Previous chemical studies of such structures, grown on F-doped SnO 2 and In 2 O 3 substrates, have demonstrated [2][3][4] a great amount of inter-diffusion of halogens; metals: Au, Cu; non-metal elements: O, S, Cu and Te through the solar cell structure.…”