Layered Graphene/Quantum Dots for Photovoltaic Devices

摘要

To meet the increasing demand of clean energy the harvesting of electricity from solar incident photons with high efficiency at economically viable cost is needed. Quantum dot (QD) based solar cells are poised to play a leading role in this revolution owing to their potential in exceeding the Shock-ley-Queissar limit, their size-tuned optical response, and their efficient multiple carrier generation. A major challenge in developing high-performance QD solar cells is the effective separation of photogenerated electron-hole pairs and the transfer of the electrons to the electrode. Strategies that have been tried include the introduction of nanomaterials with a suitable band energy as efficient acceptors. Carbon, an environmentally friendly and inexpensive material, exists in a variety of nanostructures ranging from insulator/semiconducting diamond to metallic/semimetallic graphite, conducting/semiconducting fullerenes, and single-walled carbon nanotubes (SWNTs), and recently has been widely used in QD solar cells. Particularly, SWNTs and stacked-cup carbon nanotubes have been used as efficient acceptors to enhance photoinduced charge transfer for improved performance because of their unique one-dimensional nanostruc-ture and appropriate band energy. However, the efficiency of carbon nanomaterial based QD solar cells reported so far is still low (incident photon-to-charge-carrier conversion efficiency (IPCE) <5% and photocurrent response < 0.4 mA cm~(-2) under light illumination of 100 mWcm~(-2)), which is still some distance from the requirement for the next generation of solar cells.