Doped III-V Quantum Dots for Enhanced Light Harvesting

As demand for value added chemicals ever increases with population growth, new methods must be established to perform the complex chemical reactions required to create said products. Photocatalysis is a potential avenue to perform these reactions, using photoexcited materials to serve as a source of high energy electrons involved in more complex processes. However, creating efficient photosenitizers is a non-trivial task and must be painstakingly designed for high efficiency.<br/>Shelled semiconducting nanocrystals (also known as shelled quantum dots) have two the main characteristics required for efficient light harvesting/photosensitization. These qualities are high absorption coefficients (up to 10⁵ cm^-1 M^-1) and robust photostability. However, the shell that imparts the increased absorption coefficient and photostability also traps charge carriers in the core. This leads to charge carriers with high overlap, leading to short excited-state lifetimes on the scale of tens of nanoseconds. This disadvantage can be mitigated by the introduction of a dopant such as Ag⁺or Cu⁺ which causes the excited state lifetime to increase to hundreds of nanoseconds. We can measure electron transfer from these quantum dots to molecular acceptors via photoluminescence and transient absorption spectroscopies. In doing so, we see that the doped quantum dots exhibit enhanced electron transfer by up to a factor of 10. Finally, we use examine the electronic structure of these materials <i>in silico</i> to determine why the charge transfer is so greatly increased upon doping.