Doping for Speed: Colloidal Nanoparticles for Thin-Film Optoelectronics

Abstract

Solution-processable semiconductor materials ranging from conjugated polymers and small organic molecules to colloidal inorganic nanoparticles are being studied for applications in both low-cost solar cells and photodetectors. High-quality thin films of many inorganic semiconductors can be prepared by techniques such as chemical vapor deposition, molecular beam epitaxy, and atomic layer deposition. In contrast, preparing device-quality films of inorganic materials from colloidal solutions can be more difficult due to the challenge of achieving well-defined doping, controlled trap densities, and reproducible surface chemistry. Nevertheless, solution deposition using colloidal precursors is an attractive goal because of the potential for low-cost, large-area processing. In recent years, a great deal of effort has focused on the colloidal synthesis of wide-band-gap metal oxides such as TiO(2), visible-absorbing II-VI compounds such as CdSe, and small-band-gap materials such as PbSe. Much of the work on visible- and IR-absorbing photodetectors has been done on materials containing metals such as Cd and Pb. A new paper in this issue demonstrates photoconductive detectors made from Cu-containing In(2)S(3) nanoplates. The incorporation of Cu into the In(2)S(3) nanoplates leads to a significant decrease in the lifetime of the photoexcited carriers, resulting in significantly faster response times for the photodetectors processed from colloidal solution.

Design Considerations for Plasmonic Photovoltaics

“…Although the absorption of these quantum confined structures is well matched to the solar spectrum, making efficient photovoltaics has been challenging. CdSe quantum dots blended with conducting polymers have reached efficiencies of 2%, and fully inorganic cells have reached efficiencies of 3% 63. One of the limiting factors is the carrier transport through the quantum dot layer, and the highest efficiency cells to date use elongated nanorods to improve transport 64…”

Towards a universal organogelator: A general mixing approach to fabricate various organic compounds into organogels

“…In order to make hybrid functional materials, inorganic nanoparticles can be either in situ produced or be doped inside the organic soft materials [58][59][60]. In this context, there has been a number of reports focusing on the doping of nanoparticles into polymers, the hybrid materials with improved performance can thus be obtained [61,62]. The gels based on LMOGs are very important soft matters.…”

AFM‐based photocurrent imaging of epitaxial and colloidal QDs

“…Solution-processable QDs belong to a newly emerging family of photoactive materials. Easy processing and their sizetunable excitation properties make these colloidal crystals attractive for integration with photodetectors or photovoltaic devices [2]. They are most often used in combination with an organic charge transporting material and pcAFM can show how photoactive and conductive properties of the film depend on sample morphology and composition.…”