The Effect of the CdCl2 Heat Treatment on CdSexTe1-x Solar Cells

In this paper we report results on CdSe
_x
Te
_1-x
based solar cells, fabricated by inter-diffusing CdTe/CdSe bilayers. The effect of the CdCl
₂
heat treatment (HT) carried out at various temperatures on bilayers with different CdSe thicknesses has been investigated. The CdCl
₂
HT temperature has been found to be critical for intermixing; to-date it has been shown that higher temperature leads to enhanced inter-diffusion, which also leads to higher short circuit current (J
_SC
) due to a decrease in the band gap of the absorber. Large CdSe thicknesses (> 300 A) lead to lower open circuit voltage (V
_oC
) and fill factor (FF). Optimization of the annealing temperature and CdSe thickness has yielded cells with V
_oC
= 850 mV, J
_SC
= 26.3 mA/c m
²
, FF= 73 % and efficiency 16.3%.