Getting the Best of Nanomaterials: Intercalated Graphene/Quantum Dot Hybrid Photodetector: Nano Seminar Series

Seminar | September 28 | 2-3 p.m. | 390 Hearst Memorial Mining Building | Note change in date

 Prof. Oscar Vazquez Mena, UC San Diego, NanoEngineering

 Berkeley Nanosciences and Nanoengineering Institute

Recently, hybrid graphene quantum dot (Gr/QD) systems have emerged as high responsivity photodetectors, taking advantage of the high charge carrier mobility of graphene and the high light absorption of PbS quantum dots. However the performance of this hybrid system is still limited by the charge carrier diffusion length of quantum dots, which remains the main bottle neck for quantum dot based photovoltaics.

In this talk, we will present a novel configuration that overcomes the short carrier diffusion length in QDs by using multiple intercalated graphene collectors, instead of a single junction, for more efficient photogenerated charge collection. The key factor in our design is spacing the Gr layers at a distance shorter than the diffusion length, allowing to efficiently collect the photocarriers before they recombine. This strategy overcomes the known limitation in photodetection and photovoltaics that light absorbing layers cannot be thicker than the minority carrier diffusion length.

Our intercalated devices deliver 10x higher photoresponse than non-intercalated devices (10E7 to 10E8 A/W) with a broad spectrum photoresponse. The main outcome of this work is showing that nanoscale materials can be combined and integrated into a single structure, allowing to combine and tune their physical properties to optimize device performance.

Furthermore, we will discuss potential applications such as multicolor pixels, and high-efficiency intercalated graphene/quantum dot photovoltaic devices.