Construction and Analysis of PbSe Quantum Dot Heterojunction Solar Cells.

摘要

PbX (X = S, Se, Te) quantum dot (QD) thin films have the potential to push photovoltaic efficiencies over the Shockley-Queisser limit. The focus of this thesis is the development of a robust and reproducible process for making thin film PbX QD heterojunction solar cells (HSC). Literature already has several examples of methods used to optimize the synthesis and film deposition techniques for PbX QD devices. So experiments here are designed to optimize the sputtering conditions and material selection for the metal oxide window layers. PbSe QDs treated with 1,2-ethanedithiol (EDT) are well suited to be the conductive absorber layer of HSCs. The sputtering conditions and post deposition processing of metal oxide window layers, ZnO and SnO2 thin films, are correlated with HSC performance. Junctions made of 1.4 eV PbSe QDs and ZnO produce HSCs with an average efficiency of 2.9% (+/- 0.1%), while SnO2 is a better match with 1.1 eV PbSe QDs with an average efficiency of 0.9% (+/- 0.1%). Photovoltaic performance is very sensitive to the relative band positions of the metal oxide window layer and PbSe QDs. However, this sensitivity is confined to the interface of the heterojunction. Changing the bulk material of the window layer had no detectable impact on the performance of the PbSe QD HSCs. This demonstrates the need for precise control of material surface properties and interfacial engineering. impact on the performance of the PbSe QD HSCs. This demonstrates the need for precise control of material surface properties and interfacial engineering.