# Luminescence Materials for Dye-Sensitized Solar Cells: Advances and Directions
## 4 Luminescent Materials in DSSCs
### Energy Transfer  
Energy transfer from luminescent materials to dye molecules can occur through mechanisms such as Forster resonance energy transfer (FRET). This process enhances the excitation of dye molecules, boosting the efficiency of the DSSC. The FRET may be used in DSSCs to connect two or more materials in order to enhance strong absorption across a wide range of the solar spectrum and improve device performance [87, 88]. Luminescent nanoparticles and organic dyes are particularly effective in facilitating these energy transfer processes. Figure 8 depicts the energy level diagram of the energy transfer from the luminescent material to the dye molecules. Energy from the emission transition of the luminescent material is transferred to the dye molecules. The photon absorption of the dye molecules produces excited electrons from its highest occupied molecular orbital (HOMO) in the ground state to the lowest unoccupied molecular orbital (LUMO) in the excited state. The excited electrons are rapidly injected into the conduction band of the TiO\({}_{2}\), which lies below the excited state of the dye, where they diffuse through the nano-porous structure to the FTO back contact and eventually flow through the external circuit. In the quest to enhance the efficiency of dye-sensitized solar cells (DSSCs), the concept of energy transfer from luminescent materials to dye molecules has gained significant attention. This process can improve light harvesting and facilitate better utilization of the solar spectrum, particularly by extending the absorption range from the visible to the UV and NIR regions where the device has weak spectral responsivity, thereby enhancing the photon absorption of the dye molecules and increasing charge carrier generation. This section explains the mechanisms of energy transfer, the types of luminescent materials involved and their impact on DSSC performance. \begin{table}
\begin{tabular}{l l l l l} \hline \hline
**Luminescent Materials** & \(\mathbf{V_{ac}}\)**(mV)** & \(\mathbf{J_{ac}}\)**(mA/cm\({}^{2}\))** & **FF (\%)** & \(\mathbf{\eta}\) (\%)** & **Reference** \\ \hline GQD\({}_{2}\) & 653 & 22.62 & 53 & 7.82 & [81] \\ BP/RTQDs & 718 & 16.3 & 68.5 & 8.02 & [82] \\ C\({}_{100}\)-CQDs & 404 & 0.306 & 44 & 0.0544 & [83] \\ TIC\({}_{4}\)+N719+GQDs & 660 & 4.11 & 73 & 2.00 & [84] \\ PANI-GQDs & 440 & 9.3 & 39.1 & 1.6 & [85] \\ NCQD DSSC \({}^{\star}\) & 710 & 18.13 & 63.7 & 8.75 & [86] \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Photovoltaic parameters of best DSSCs with different types of quantum dots materials. \begin{table}
\begin{tabular}{l l l l l l} \hline \hline
**Luminescent Materials** & \(\mathbf{V_{ac}}\)**(mV)** & \(\mathbf{J_{ac}}\)**(mA/cm\({}^{2}\))** & **FF (\%)** & \(\mathbf{\eta}\) (\%)** & **Reference** \\ \hline Y\({}_{2}\)CaZnO\({}_{3}\):Er\({}^{3+}\)/Yb\({}^{3+}\) & 710 & 13.28 & 64 & 6.01 & [63] \\ BaCdF\({}_{3}\):Er\({}^{3+}\)/Yb\({}^{3+}\) & 730 & 16.0 & 65.82 & 7.72 & [64] \\ LiYF\({}_{4}\):Er\({}^{3+}\)/Yb\({}^{3+}\) * & 660 & 22.16 & 72 & 10.53 & [65] \\ Lu\({}_{0}\)O\({}_{3}\):Tm\({}^{3+}\), Yb\({}^{3+}\) & 757 & 13.41 & 65.3 & 6.63 & [66] \\ CaCe(MoO\({}_{4}\)):Er\({}^{3+}\)/Yb\({}^{3+}\) & 670 & 28.9 & 41 & 7.78 & [67] \\ Y\({}_{2}\)O\({}_{3}\):Er\({}^{3+}\), Yb\({}^{3+}\) & 760 & 13.68 & 64.32 & 6.68 & [68] \\ Y\({}_{2}\)O\({}_{3}\):Ho\({}^{3+}\)/Yb\({}^{3+}\) & 710 & 21.9 & 51.29 & 7.59 & [69] \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Photovoltaic parameters of best DSSCs with different types of up-conversion materials.