Solar cell with double quantum dot structure

  • Amin Habbeb Al-Khursan Nassiriya Nanotechnology Research Laboratory (NNRL), Science College, Thi-Qar University, Nassiriya, Iraq
  • Suha Hadi Nassiriya Nanotechnology Research Laboratory (NNRL), Science College, Thi-Qar University, Nassiriya, Iraq
Keywords: double quantum dot solar cell, electron-hole model, excitonic model, recombination rate, band-to-band, quantum efficiency


In this work, a double quantum dot (QD) structure is introduced as an intermediate band for highperformance
solar cells (SCs). Coupling the dynamical (density matrix) equations with the continuitycurrent
equation and solving them numerically to obtain the quantum efficiency (QE). which allowed to
address the interaction between all the states and band of SC which is not possible elsewhere and better
than the rate equation modeling. Throughout this modeling, the momentum matrix elements of QD-QD,
QD-wetting layer (WL), and WL-barrier transitions are calculated and the orthogonalized plane wave is
assumed for WL-QD transitions. Results are simulated both the excitonic and non-excitonic (electronhole
eh) cases and exhibit the importance of adding the QD layer.
The valence band (VB) DQD states have similar occupations while the conduction band (CB) is
not. The WL occupations are the smallest in both CB and VB as it works like a reservoir. These results
confirm both the importance of adding the intermediate band (QD layer) and the carrier scenarios. The
band-to-band recombination rates in the DQD structure are modulated with the energy difference. The
VB relaxation rates between states are of the same order and lower than the corresponding CB rates related
to their occupation. The occupations in the excitonic model do not much differ from the eh model. A few
increments in the excitonic model in the CB and VB barrier-WL relaxation while a reduction in the VB
WL-QD and QD-QD relaxation appears. The band-to-band recombination rates in the excitonic model
are reduced compared to the eh model. The photo-generation rates have the highest rate at QDs. The
quantum efficiency (QE) in the eh model is increased at semi-linear relation with VB relaxation rates
while it is increased exponentially with CB rates. Longer relaxation times for WL-QD check it pleas
transitions are attained with a wider energy difference. For the DQD structure, the longer relaxations and
band-to-band recombinations are accessed depending on the wider energy difference


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