Thuc-Quyen Nguyen

Solution-Processed Organic Solar Cells: Current Progress and Challenges  

Organic solar cells potentially can offer low cost, large area, flexible, light-weight, clean, and quiet alternative energy sources for indoor and outdoor applications. In this talk, I will give an overview of the current progress and challenges in organic solar cells. Then, I will discuss recent progress at UCSB on the development of molecular donor materials for application in solution processed bulk heterojunction solar cells. Molecular donors offer potential advantages over conjugated polymer systems in terms of their ease of synthesis and purification; making them more affordable to produce on large scales. Additionally, small molecules do not suffer from molecular weight dependence and polydispersity, and thus large batch-to-batch variation as their polymer counterparts. The molecular design is based on donor/acceptor/donor or acceptor/donor/acceptor using common building blocks such as oligothiophenes, dithieno silole (DTS), pyridal thiadiazole (PT), diketopyrrolopyrrole (DPP), etc. Chemical structure and processing conditions be used to tune the energy level, bandgap, solubility, molecular packing, film morphology, exciton diffusion, charge mobility, charge recombination, and therefore, the device performance. A series of compounds has been synthesized to establish structure-function-property relationships. A combination of techniques is employed to characterize material properties including steady-state and time-resolved spectroscopy, atomic force microscopy (AFM), photoconductive AFM, TEM, XRD, UPS, and GIWAXS. The results from these studies provide design guidelines for new generation of molecular-based materials for applications in organic solar cells.