Flexible, Lightweight Quantum Dot Solar Cells Using Plasmonic-Enhanced Light Absorption

During the course of this fellowship I explored several lightweight, solution-processable photovoltaic materials and improved the power conversion efficiency and durability of solar cells fabricated from these novel materials. The emphasis of this work focused on novel materials that could be incorporated into flexible, lightweight solar cells as opposed to the development of the flexible device architectures. My initial exploration of the ZnS-AgInS2 (ZAIS) nanoparticle-based solar cells yielded an improvement in organic P3HT:PCBM photovoltaics through the inclusion of the ZAIS nanoparticles (NPs) in the active layer. We selected ZAIS NPs because of the simple heat-up synthesis and non-toxic chemical composition. By tuning the composition of the NPs, or more specifically by tuning the ratio of ZnS to AgInS2, we were able to tune the bandgap for various optoelectronic applications. Flexible organic solar cells had already been demonstrated in the literature; therefore, I focused on improving the efficiency of the active layer by incorporating NPs that could enhance the charge separation and transport in the polymer solar cells. •Added ZnS-AgInS2 nanoparticles to solution-processable polymer photovoltaic devices to achieve an increase in power conversion efficiency from 2.50% up to 2.89%. This improvement was due to an increase in fill factor from 47% up to 50%. In order to achieve this result, the ZnS-AgInS2 nanoparticle synthesis yield was increased and a pyridine ligand exchange was developed. To the author’s knowledge, this was the first report of a ZnS-AgInS2 nanoparticle and polymer hybrid solar cell. • Fabricated thin film, solution-processable MAPbI3 perovskite solar cells with power conversion efficiencies exceeding 13%. • Benchmarked the operational lifetime of MAPbI3 perovskite solar cells using the standard n-i-p device architecture with ISOS-L1 stability testing protocols (i.e. constant illumination, resistive load, ambient laboratory condition.) • Characterized degradation of MAPbI3 perovskite solar cells and determined that devices with MoOx/Al electrodes are more stable than devices with conventional Au or Ag electrodes. Prior to this study, most reports in the literature had claimed that Au was a stable, inert metal electrode. • Developed a film deposition method for CsPbI3 quantum dots, which yields an airstable, room-temperature stable film of CsPbI3 in the desired cubic perovskite crystallographic phase. • Developed a solution-processed AX-treatment for CsPbI3 quantum dot films that up to doubles the film mobility. Using different AX salts (e.g. FAI, MAI, FABr, MABr, CsI) provides tunability. Solar cells fabricated with the AX-treated CsPbI3 quantum dots observe enhanced short-circuit current, without any losses in fill factor or opencircuit voltage. Page 6 – Revised 04/2017 • Achieved an NREL-certified record quantum dot solar cell efficiency of 13.4%. The previous quantum dot solar cell record efficiency on the NREL PV efficiency chart was