State filling effects on photoluminescence and photovoltaic characteristic of aluminium-doped CdTe colloidal quantum dots stabilized in aqueous medium

CdTe and aluminium (Al)-doped CdTe (Al:CdTe QDs) colloidal quantum dots (QDs) were synthesized through an aqueous route. CdTe and Al:CdTe QDs colloidal quantum dots of different size were obtained by collecting the samples at different refluxing time. The size of the synthesized QDs collected after 6 h of refluxing time was measured to 3.3 and 4.8 nm for Al:CdTe QDs and CdTe QDs, respectively. The size shrinkages of Al:CdTe QDs were due to chlorine ions from AlCl3 precursor, which controls the growth kinetics of QDs and stabilizes the QDs in the aqueous phase. The size shrinkages of Al:CdTe QDs result in an increase of bandgap from 2.13 to 2.3 eV and congruently blue-shifted absorbance and emission spectra were discerned. The state filling effect, gradual filling of energy state, observed clearly in photoluminescence spectra of Al:CdTe QDs for samples collected after 30 min of refluxing time. We also fabricated Gratzel-type QDs-sensitized solar cells by loading CdTe and Al:CdTe QDs on mesoporous TiO2 photoanode. Photovoltaic efficiency is marginally increased (13%) from 0.45 to 0.51% for Al-doped CdTe QDs as compared to CdTe QDs.

Automated summary

CdTe and Al-doped CdTe colloidal quantum dots were synthesized through an aqueous route, with different sizes obtained by varying refluxing time. The Al-doping led to smaller size and increased bandgap, resulting in blue-shifted absorbance and emission spectra. Fabrication of Gratzel-type QDs-sensitized solar cells showed a marginal increase in photovoltaic efficiency for Al-doped CdTe QDs compared to CdTe QDs.