|Title||Towards highly efficient and cheap third generation solar cells based on type-II colloidal quantum dots|
Colloidal quantum dots (CQD) have size-dependant spectral response and thus they have promising future for many applications, including third generation solar cells. Multiple exciton generation (MEG) is a process of producing more than one exciton by absorbing one energetic photon in CQDs, increasing the efficiency of photovoltaics considerably. Electrons and holes are confined in different volumes of type-II CQDs whereas, both carriers localise in the same volume of type-I CQDs. The growth of different core sizes and shell thicknesses in type-II CQDs will control carrier wavefunction overlap and hence the sign and magnitude of multi-exciton intearction energies in this type of structures. In this study, ultrafast transient absorption spectroscopy was used to study both CdSe/CdTe/CdS and CdTe/CdSe/CdS core/shell/shell CQD. Analysis of the transient absorption spectra of various samples yielded large attractive interaction energies of 30-50 meV which is completely opposite to the previously attained repulsive results. In addition MEG efficiency in these samples were also measured. It was found that MEG efficiency in these structures was about three times higher than the previously reported results. The results show that CQD engineering can be used to significantly enhance the solar cell efficiency.
Musa Çadırcı earned his BSc in Physics from Fırat University, Turkey, in 2007 and his MSc and PhD in Photon Physics from the University of Manchester, UK, in 2010 and 2014, respectively. His research interest is picosecond carrier dynamics of colloidal quantum dots. In particular, he investigates multiple exciton generation and exciton-exciton interaction in type-II quantum dots. The methods he uses are femtosecond transient absorption, time-resolved photoluminescence and steady-state absorption and photoluminescence spectroscopies.