Dear Sajid, many thanks for asking this very interesting and important technical question. To my knowledge, mainly manganese (Mn) and cobalt (Co) have been used as dopants in quantum dot sensitized solar cells (QDSSCs). According to the article cited below, transition metal dopants are applied to improve the current density and energy conversion of QDSSCs:

The Influence of Dopant Concentration on Optical-Electrical Features of Quantum Dot-Sensitized Solar Cell

This article has been published Open Access and is freely available as public full text (see attached pdf file)

For the use of manganese as dopant, please also have a look at the following potentially useful research articles:

Giant photocurrent enhancement by transition metal doping in quantum dot sensitized solar cells

Article Giant photocurrent enhancement by transition metal doping in...

and

Mn-Doped Quantum Dot Sensitized Solar Cells: A Strategy to Boost

Efficiency over 5%

Article Mn-Doped Quantum Dot Sensitized Solar Cells: A Strategy to B...

Here it is stated e.g. that "the transition metal dopants in QDs have the potential to introduce impurity states in the band gap and enhance absorption."

The first paper has been posted by the authors as public full text on RG so that you can freely download it as pdf file. Unfortunately this is not true for the second paper. However, both authors have RG profiles so that there is a good chance that you can request the full text directly from the authors via RG.

I hope that these references are useful for you. Good luck with your research and best wishes, Frank Edelmann

Both manganese (Mn) and cobalt (Co) are used as dopants in quantum dot sensitized solar cells. The transition metal dopants are applied to improve the current density and energy conversion.

Thank you very much Prof.Hadi Jabbar Alagealy.