Effects of plasmonic nanostructures on the electrical properties of organic solar cells

Professor Choy, Wallace Chik Ho   (Principal Investigator (PI))

Professor Hou Jianhui   (Co-Investigator)

Professor Chew Weng Cho   (Co-Investigator)

36

2013-01-01

700000

Effects of plasmonic nanostructures on the electrical properties of organic solar cells

electrical properties, metallic nanostructures, organic/polymer semiconductors, plasmonic nanostructures, thin-film solar cells

Photonics

Engineering (E)

HKU 711612E

General Research Fund (GRF)

2012

Completed

1) Building models for physically understanding electrical properties of plasmonic OSCs An electrical model will be developed by solving 2D and 3D semiconductor equations with the consideration of metallic/organic interface effects and properties of polymer blends including exciton dissociation, bimolecular recombination, etc. Then, by integrating the optical model (developed under grant#HKU712010E) and electrical model, the multiphysics model for OSCs incorporating with arbitrary 2D and 3D metallic nanostructures will be developed. 2) Studying interface recombination/injection between metal and polymer The important mechanism of interface recombination/injection between metal and polymer can be investigated experimentally and theoretically through incorporating metallic NPs into a polymer active layer. By appropriately designing device structures, the dark current which strongly depends on the metallic/organic interface will be studied. According to the recombination/injection model by Scott and Malliaras, the dark current will be affected by the barrier height (between polymer and metallic NPs) and built-in electric field. The roles of barrier height and built-in electric field on the interface recombination/injection mechanism will be studied by changing functional groups and concentration of metallic NPs. The measured dark current-density (J)- voltage (V) characteristics will be analyzed with theoretical results for understanding the physics and evaluating the characteristic parameters of the model. 3) Investigating the effects of non-uniform exciton generation in plasmonic nanostructures With the understanding of PR mechanism in active layer and the spectral overlap engineering between PR and polymer absorption-band from our work (grant#HKU712010E), the guideline to maximize PR enhanced exciton generation (due to the enhanced absorption) will be explored. Since PR produces regionally-concentrated near-field in the active layer, a non-uniform exciton generation will occur. The recombination loss will change due to the non-uniform exciton generation and thus will be theoretically and experimentally investigated. Meanwhile, it is possible that SCLC will be present due to the PR-induced non-uniform carrier formation and unbalance carrier mobilities of typical polymers. SCLC effects can be characterized by the slope of J-V curve and light-intensity dependent short-circuit current. We will first study localized PR (LPR) devices through incorporating metallic NPs into OSCs. We will investigate how recombination loss and SCLC affect the electrical properties of OSCs with different parameters (e.g. active layer thickness, polymer mobility, and metallic NP location in device structures). In the meantime, we will study the change of OSC electrical properties due to surface PRs (SPRs) through metallic grating nanostructures with different grating parameters (including grating period and depth), metals and device architectures. 4) Optimizing the electrical and optical properties of plasmonic OSCs With our knowledge on the optical properties (grant#HKU712010E), we will optimize the electrical and optical properties through combining the metallic NPs and nanogratings for ""double"" plasmonic nanostructures (including both LPR and SPR) in single-unit OSCs. We will study the metallic nanostructure material (Ag, Au, etc), concentration, location and surface functional group of metallic NPs, metallic nanograting geometry, as well as thickness and carrier mobility of polymers in active layer for realizing practical plasmonic OSCs. Besides commercially available materials, we will investigate various polymers from Prof. Jianhui Hou (Co-I of this proposal) for optimizing device performances. 5) *** Note: In order to show our capability to manage the project, we have already started to work on Objective 1 and obtained some preliminary results as discussed in ""Research Plan and Methodology"".