Interface engineering in inorganic-absorber nanostructured solar cells
- The focus of this work is variants on the dye-sensitized solar cell (DSSC) that employ inorganic materials as the light absorber, replacing the organic dye molecules used in DSSCs. Such DSSC-inspired devices are emerging technologies in the broader class of thin film solar cells, and include quantum-dot sensitized solar cells (QDSSCs) and perovskites solar cells (PSCs). Quantum-dot sensitized solar cells employ semiconductor nanocrystals, or quantum dots, as the light absorber. The band gap of quantum dots varies with size, allowing for a tunable absorption onset in these devices, among other benefits. PSCs, in which the absorber is CH3NH3PbI3, or variants thereof, with the perovskites crystal structure, first attracted attention in 2012 and have shown an unprecedented rise in efficiency to current record values of 20.1%. QDSSCs and PSCs can be fabricated completely from solution processed materials that can be low-purity, contrasting favorably with the industrial standard, silicon solar cells, which require expensively-processed, high-purity silicon. This tolerance to defects is partially due to the nanostructured design of some PSCs and all QDSSCs, in which a nanostructured bulk heterojunction is formed between the electron-transport material, the absorber, and the hole-transport material. However, the high interfacial areas involved in such designs leads to high rates of interfacial recombination, causing losses in photocurrent, and limiting device efficiency. In this work, I will present methods to reduce interfacial recombination in these inorganic-absorber nanostructured solar cells though surface modifications. In QDSSCs, these include growing ultra-thin insulating metal oxide films by atomic layer deposition (ALD) at the interface and controlling of the nucleation and growth of the inorganic absorber. These studies provide insight into the working mechanisms of QDSSCs, through a combination of the highly-controlled nature of ALD, where films can be grown a single atomic layer at a time and an interface can be atomically engineered, X-ray absorption measurements of interfacial geometric and electronic structure, and detailed studies of the resulting solar cell performance. I will also detail the use of ALD to grow entire material layers in perovskites solar cells, both ALD TiO2 as the electron-transport material, and ALD NiOx as the hole-transport material. Despite their high efficiencies, PSCs are unstable and rapidly degrade when exposed to moisture or excessive heat. The use of ultra-conformal inorganic layers grown by ALD to cap the perovskites absorber, instead of the currently-employed organic layers, has the potential to improve the stability, and thus efficiency, of perovskites solar cells.
|Type of resource
|electronic; electronic resource; remote
|1 online resource.
|Roelofs, Katherine Elizabeth
|Stanford University, Department of Materials Science and Engineering.
|Prinz, F. B
|Prinz, F. B
|Statement of responsibility
|Katherine Elizabeth Roelofs.
|Submitted to the Department of Materials Science and Engineering.
|Thesis (Ph.D.)--Stanford University, 2015.
- © 2015 by Katherine Elizabeth Roelofs
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
Also listed in
Loading usage metrics...