Colloidal Quantum Dot Photovoltaics
Clean, renewable sources of energy are of utmost importance to meet the increasing worldwide demand. In particular, solar energy is a remarkably abundant source: the amount of sunlight hitting the earth’s surface in one hour is enough to satisfy humanity’s annual energy needs many times over. However, solar currently represents a minute portion of the current energy mix; reductions in materials and installation costs are required to accelerate adoption.
Colloidal quantum dots (CQDs) are nanometre-scale semiconductor particles synthesized in and processed from solution. This allows the use of CQD inks to be painted onto flexible substrates for rapid, low-cost fabrication of solar cells. Additionally, CQDs exhibit quantum size effect tunability. This allows the absorption range of CQD films to be tuned, based simply on nanocrystal size, across the entire solar spectrum. Since half of the available solar energy lies in the infrared range, CQDs are able to access photons unusable by other photovoltaic materials. Our group reported the first infrared-sensitive CQD solar cell in 2005, and has been a leader in the field since then.
Our interdisciplinary research on CQD solar cells spans theoretical modeling, materials design, and device engineering. Through these, we aim to advance the efficiency of low-cost CQD solar cells and have certified the first CQD cell with efficiency over 10%. Our continuing research includes investigating the role of surface ligands on CQD surfaces in determining electrical properties and device stability. We are also developing methods to make coating solar cells faster and cheaper, including by spraying CQDs on flexible substrates. By exploiting the infrared sensitivity of CQDs, we are exploring methods of augmenting other photovoltaic materials by absorbing otherwise wasted long-wavelength light.