Exploiting Nanocrystal Properties to Enhance Metal Halide Perovskite Optoelectronic Devices

Metal halide perovskites (MHPs) are one of the most-researched semiconductors today. They have become the fastest improving solar cell material yet discovered, with efficiencies starting at 3.8% in 2009 and growing to over 25% today. These materials are unique because they are able to combine a low-cost solution-processing capability with excellent optoelectronic properties that are comparable to, and often even surpass, traditional semiconductor single crystals. As such, halide perovskites are being explore for many optoelectrical devices such as LEDs, lasers and photodetectors. However, there is still much work to be done to in order to circumvent the current charge trapping limitations in halide perovskite technologies. The present work will examine the use of nanoparticles (NPs) to provide unique avenues to address these limitations.
In the first part of this work, I leverage the advantageous properties of MHP NPs and use them as a rapid and high-throughput experimental testing platform to conduct a comprehensive examination of over 20 different molecules to passivate the MHP surface. Utilizing this novel screening method, tri¬-n-butylphosphine was identified as an effective molecule to passivate surface charge trap sites. This improvement in charge trap passivation was then translated from the NP model system to MHP thin films and solar cell devices to demonstrate for the first time, that the findings of the NP testing platform can be directly applied to thin film systems.
In the second part of this work, I utilize lead sulfide (PbS) NPs as emission centers embedded in a MHP-based radiation scintillator device. MHPs have a myriad of beneficial properties that make them excellent candidates for radiation scintillators, but they also possess several significant limitations for realizing this potential. Taking advantage of the optoelectronic properties of PbS NPs, I create a hybrid NP-in-MHP scintillator material with the capability to detect and identify radioisotopes. This novel scintillator material leverages the combined optoelectronic and the low-cost solution-processing capabilities of MHPs and NPs to create a scintillator material unlike any other available today thus meeting a significant need in the scintillator market.