Quantum Dot Sensitized Solar Cells with Improved Efficiency Prepared Using Electrophoretic Deposition

Abstract

Quantum dot sensitized solar cells (QDSSC) may benefit from the ability to tune the quantum dot optical properties and band gap through the manipulation of their size and composition. Moreover, the inorganic nanocrystals may provide increased stability compared to organic sensitizers. We report the facile fabrication of QDSSC by electrophoretic deposition of CdSe QDs onto conducting electrodes coated with mesoporous TiO(2). Unlike prior chemical linker-based methods, no pretreatment of the TiO(2) was needed, and deposition times as short as 2 h were sufficient for effective coating. Cross-sectional chemical analysis shows that the Cd content is nearly constant across the entire TiO(2) layer. The dependence of the deposition on size was studied and successfully applied to CdSe dots with diameters between 2.5 and 5.5 nm as well as larger CdSe quantum rods. The photovoltaic characteristics of the devices are greatly improved compared with those achieved for cells prepared with a linker approach, reaching efficiencies as high as 1.7%, under 1 sun illumination conditions, after treating the coated electrodes with ZnS. Notably, the absorbed photon to electron conversion efficiencies did not show a clear size-dependence indicating efficient electron injection even for the larger QD sizes. The electrophoretic deposition method can be easily expanded and applied for preparations of QDSSCs using diverse colloidal quantum dot and quantum rod materials for sensitization.

Colloidal PbS and PbSeS Quantum Dot Sensitized Solar Cells Prepared by Electrophoretic Deposition

“…QDs were deposited on both the cathode and anode electrodes similar to previous reports. 18 Fresh layers at each deposition time were taken from the electrophoretic cell, rinsed several times with toluene to wash off unbound QDs, subsequently rinsed with ethanol, and dried at room temperature. After electrophoretic deposition colloidal QDs were coated with a CdS layer grown by SILAR.…”

Advancing colloidal quantum dot photovoltaic technology

“…Performing ligand exchanges, where the original lengthy ligands are substituted for shorter bifunctional ligands, has improved CQD loading due to the enhanced anchoring of CQDs to the titania electrode [160,161]. Alternative loading methods, including a pressing technique [162] and electrophoretic deposition [163], have led to improved CQD loading and elimination of regions exposed to the redox electrolyte. In recent studies, pH control was demonstrated to increase quantum dot loading as well as reduce interfacial recombination in CQD-SSC devices [164,165].…”

Morphology of Electrophoretically Deposited Films on Electrode Strips

“…Adaptive mesh refinement was utilized over the course of the simulation to increase mesh density near large gradients in volume fraction. The solution to (8) was found using the built-in electrostatics module, while (9) was implemented as a generic PDE. Time stepping was performed using the BDF method with a MUMPS solver.…”