Do grain boundaries assist S diffusion in polycrystalline CdS/CdTe heterojunctions?

Abstract

We report on a transmission electron microscopy and energy-dispersive x-ray spectroscopy study of S diffusion in polycrystalline CdS/CdTe heterojunctions. We find that grain boundaries significantly assist S diffusion in the CdTe layer when the CdTe is grown without the presence of oxygen, i.e., the S diffuses more easily along the grain boundaries than in the grains. However, grain boundaries do not enhance the S diffusion in CdTe when it is grown in the presence of oxygen. The reason is likely to be the formation of Cd–O bonds at the grain boundaries, which are resistance to the S diffusion.

Fischer‐Tropsch Synthesis Over Co‐Ru/γ‐Al2O3 Catalyst in Supercritical Media

“…1 show that the CO conversions for gas phase FTS are 43 % and 54 %, respectively, and 63 % for supercritical-hexane phase. Huang and Roberts [1] and Yan et al [21] obtained similar results using a Co catalyst with different total pressure, as shown in Tab. 1.…”

“…The different aspects of the various types of reactors have been described in detail [1,[3][4][5], so that the FTS has been studied or commercially operated in fixed, slurry and fluidized-bed reactors [1]. The FTS processes in both the slurry and gas phases have advantages and disadvantages that have been discussed previously by many researchers [1,5,[6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21].…”

Photoluminescence studies of CdTe films and junctions

“…The properties of the band gap states can influence the recombination of carriers through the CdTe junctions, and as a result the efficiency of the CdS/CdTe solar cells. It is reasonable to expect that the recombination levels in CdTe layers and especially in the interface layer of the heterojunctions will be influenced by diffusion of S atoms from the CdS layer during the deposition and annealing processes [2]. In order to establish the influence of the impurity atoms diffused in CdTe, the PL spectra have been obtained from the "free" CdTe surface and from the interface of the heterojunctions, as indicated in the previous section.…”

A comparative study of microstructural stability and sulphur diffusion in CdS/CdTe photovoltaic devices

“…A number of means have been utilised to investigate the diffusion of sulphur from the CdS to the CdTe absorber in solar cells; these include secondary ion mass spectrometry (SIMS) [25,26], photoluminescence spectroscopy (PL) [27][28][29] and transmission electron microscopy (TEM) combined with energy dispersive spectrometry (EDS) [16,30]. Of these methods, SIMS has the highest sensitivity and can detect impurities at a parts per million (ppm) level but suffers from limited depth resolution when investigating the deep CdTe/CdS interface, normally 3-6 μm below the back surface of the sample.…”