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47107-G10
Nanocomposite of Infrared Quantum Dots and Conducting Polymers: Possible Multiple Exciton Dissociation

Xiaomei Jiang, University of South Florida

Narrative of progress-PRF grant 47107-G10

Objectives: The goal of the first grant year (07-08) was to study exciton dissociation process in pure, untreated lead chalcogenide quantum dots (QDs): how photogenerated carriers are evolved and how to characterize them.

Status of effort: The first grant year has seen our multi-tier efforts:

1). Establishment of the technique for studying exciton dissociation

The time this grant arrived, I have just finished installations of major equipments (optical setup and thin film device fabrication apparatus) in my lab. The first three months (Sept. ~Dec. 2007) were mainly contributed in establishing the major technique employed for the above objectives: the continuous wave (cw)-photoinduced absorption spectroscopy.  

2). Secure of the sources of lead chalcogenide quantum dots (QDs)

Evident Technologies, Inc. is the sole commercial supplier for lead sulfide (PbS) quantum dots used in this project. They require a Material Transfer Agreement to be initiated between Evident and our institution (University of South Florida) in order for us to purchase their quantum dots. A negation was successfully done in parallel to effort 1). Since Jan. 2008, an institutional collaboration has been established between Drs. Witannachchi and Mukherjee's group, Dr. Zhang and our group to synthesize another type of lead chalcogenide Qd: lead selenide (PbSe) QDs.

3) development of a spectroscopic measure for photoinduced charge transfer

We have discovered a below-gap state in pure PbS QDs that has confinement dependence, and potentially can be used as an indicator to monitor photoinduced charge transfer process between the QDs and polymers ^[1]. This spectroscopic technique will guide the development of high efficiency hybrid QD/polymer solar cells, which is the ultimate goal of this two-year project.

4). Training of a graduate student on thin film solar cell fabrication

A graduate student (Jason Lewis) has been trained on how to fabricate thin film solar cells. He has been trained in Nanomanufacturing Research Center (NNRC) at USF on photolithography, photomask-fabrication, shadow mask design and fabrication and thin film nanotechnology. He was also trained on how to operate our device fabrication facilities and characterize solar cells. His first paper was submitted to Journal of Renewable and Sustainable Energy one month ago^[2].

Fig.1. Organic solar array based on P3HT/PCBM with 20-minature cells in series for power supply in MEMS device ^[2].

Accomplishments/New findings:

This year's research resulted in two high-profile journal publications ^[1,3] . Two more papers were submitted:

1). Cheng Zhang, Taina Matos, Rui Li, Eric Annih, and Sam-Shajing Sun; J. Zhang and X. Jiang, Synthesis and Characterization of Fully Regioregular Head-to-Tail Poly(3-Dodedyl-2,5-Thienylenevinylene) for Opto-Electronic Applications, submitted, (2008).

2). J. Lewis, J. Zhang and X. Jiang, Fabrication of organic solar array for applications in microelectromechanical systems , submitted, (2008).

Interactions/Transitions:

1) Participation/presentations at meetings, conferences:

Team members participated at APS 2008 March Meeting (New Orleans, Mar. 10~14.), with a poster presentation titled: ‘Optical and Transport Study of Nanocomposite Film of Polymer and PbS Quantum Dots', K1 338.

I also attended an Army Research Office conference in Raileigh, NC this August (Aug. 25-26, 2008) and had productive interaction with ARO program managers. My PRF-sponsored work was presented.

2) Collaboration/consultation:

Our lab has built up a numbers of inter-institutional collaborations with Dr. Sun's research group in Norfolk State University, and Dr. Zhai's group in University of Central Florida. Both groups have expertise in synthesizing novel polymers and have supplied out lab with their materials, which are important for this PRF project. A collaborative paper was submitted to Chem. Mater. couple of months ago ^[3].

Technical impact: The results we have obtained in the first year is of paramount importance for the continuous research effort on possible multiple exciton dissociation in hybrid solar cells, which is ongoing right now. Our findings about photoinduced charge transfer will help understand the essential process of exciton dissociation and give us a guideline to achieve high efficiency of the third generation solar cells, which has immediate impact on the cost-effective utilization of renewable energy.

Broader impact: I am very grateful the ACS-PRF grant I received. Not only has it been the major supporting fund for my beginning years, it has been a tremendous help for my potential grants from other Federal agencies such as NSF, DOE, ARO and DARPA. It enables the sustainability for my regular research activities, my participation in professional development workshops, and my attendance of scientific conferences. And more important, it has covered partial support for my graduate students. It serves as a milestone in my career development, as well as a great contribution to USF's educational programs.

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