Supplementary information files for "CdTe absorber layers grown under Cd-rich conditions by MOCVD: Impact on surface morphology and structure"

Supplementary files for article "CdTe absorber layers grown under Cd-rich conditions by MOCVD: Impact on surface morphology and structure"The analyses of surface morphology and microstructural properties of CdTe thin film absorber layers, deposited by metal organic chemical vapour deposition (MOCVD) on CdS/CdZnS/FTO-coated glass substrates as a function of different growth conditions (non–saturated or Cd–saturated growth condition and post–growth CdCl2 heat treatment) are presented. Scanning electron microscopy (SEM) images showed that the CdTe absorber surface morphology was relatively smoother with Cd-saturated growth compared to non-saturated conditions, while using a similar II/VI precursor partial pressure ratio. Microstructural characterisation using electron back scatter diffraction (EBSD) measurements indicate a strong influence of the II/VI ratios on the crystalline structure and degree of recrystallisation in Cd–saturated deposited CdTe absorber layers. CdTe absorber layers from a low II/VI ratio of 2 showed a strong Te(A1) Raman spectra band, characteristic of a Te rich composition, whilst a Cd–saturated composition was confirmed in the case of II/VI ratio of 4, as Te(A1) band was significantly suppressed. Cd–saturated grown CdTe:As (II/VI = 4), combined with a CdCl2 activation process at 440 °C, yielded optimum, highly randomized textured absorber with large grains. Reduced [111] oriented grains and suppression of Te(A1) mode was found to lead to higher VOC in devices. A high efficiency CdTe:As solar cell with a high VOC of 825 mV was measured based on the optimum growth condition for the absorber layers.© The Author(s), CC BY 4.0