High Mobility Hole Extraction Materials for Colloidal Quantum Dot Solar Cells

Johns Hopkins University, Baltimore MD

Investigators

Abstract

Nontechnical Description: Generating inexpensive electricity from sunlight could transform the way society meets its energy needs. Newer materials for solar cells, such as those based on liquid paints, are inexpensive and can be coated on a variety of surfaces; however, their power output is low compared to heavier conventional technology. The research team seeks to increase the power output of next-generation solar cells by developing new materials that more efficiently conduct electricity. The project has the potential to address broad societal goals in the development of more efficient renewable energy technologies, as alternatives to costly, polluting and unsustainable fossil fuels, by improving the power conversion efficiency of lightweight, cheap, and flexible solar materials. Research activities are integrated with a comprehensive education and outreach plan designed to introduce elementary students, undergraduates, and graduate students to the fields of nanotechnology and sustainable engineering. Research team members serve as mentors for the STEM Achievement in Baltimore Elementary Schools (SABES) program, regularly visiting elementary school classrooms in high-minority, low-income neighborhoods to engage students and teachers in hands-on engineering enrichment projects. Technical Description: The objective of this project is to build new high mobility hole extraction materials for PbS colloidal quantum dot (CQD) solar cells, addressing the efficiency-limiting factor in these devices. The materials routes being explored include new small organic molecule ligands, charge transfer dopants, PbSe-based CQD thin films, and stoichiometry-based doping control. We employ chemical synthesis, solution-processed device fabrication, and electrical and optical characterization. The three main goals of the project are to (1) solve the efficiency-limiting problem of low hole mobility in the hole extraction layer of PbS CQD solar cells using new doping strategies; (2) build proof-of-principle PbS CQD-based single- and multi-junction solar cells using the new hole extraction materials; and (3) answer fundamental questions about doping mechanisms and charge transport in nanoparticle-based thin film materials. This work aims to increase the efficiency of CQD solar cells so that they become competitive with conventional photovoltaic technology, representing a new flexible route for solar energy harvesting. The novel materials have the potential to be used in multijunction solar cells, transparent photovoltaics, flexible and wearable energy harvesting devices, and other photonic and optoelectronic technologies such as light emitting diodes and photosensors. The insights gained serve as foundations for understanding nanoscale charge transport in a wider range of structured materials systems. Research activities are integrated with an education plan that involves the development of new interdisciplinary undergraduate and graduate courses, focused on current research areas in renewable energy and nanomaterials, as well as STEM enrichment in public elementary schools in Baltimore City. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.