Solar Cells

Cadmium telluride (CdTe) is the predominant active material in thin-film solar cells. We have significantly advanced the fabrication of CdTe solar cells with solution-based colloidal NCs. By careful control of surface chemistry, grain growth, and interfacial layers, solar cells with power conversion efficiencies of up to 12% have been achieved. We have also shown that inorganic ligands such as CdCl3 can both stabilize the NCs and promote grain-growth. Several roll-to-roll friendly deposition techniques such as doctor-blading and spray-coating were also investigated. With material characterizations and optoelectronic tests, our findings support the viability of solution-processed CdTe solar cells with high performance. Through this model system, we demonstrate that the unique chemical and physical properties of colloidal NCs can be harnessed effectively in real-world application.

(Left) Cross-sectional SEM of a solution-processed CdTe solar cell with the following structure: glass/ITO/CdTe/ZnO/Al (false color added for clarity).

(Right) Current density-voltage (J-V) curve showing a high power conversion efficiency of 12.3%.

(Top) Ligand exchange with CdCl3 , which promotes colloidal stability while acting as a sintering agent.

(Bottom) Several solution-deposition techniques investigated for low-cost and scalable fabrication.

Quantum Dot Light-Emitting Diodes (QLEDs)

Our research focuses on QLEDS where a quantum dot layer acts as an emission layers in light-emitting diodes. QLEDs are generally composed of a cathode, electron transport layer, quantum dot emission layer, hole transport layer and anode. The charge transport layers facilitate charge injection from electrodes to the emission layers by reducing energy barrier between them. Our research aims to realize patternable QLEDs based on our novel ligand systems.

A typical device structure of quantum dot light-emitting diodes (left) and an energy level diagram (right).