<p>Solar photovoltaics (PV), the technology that converts sunlight into electricity, has
immense potential to become a significant electricity source. Nevertheless, the laws
of economics dictate that to grow from the current 2% of U.S. electricity generation
and to achieve large scale adoption of solar PV, the cost needs to be reduced to the
point where it achieves grid parity. For silicon solar cells, which form 90% of the
PV market, a significant and slowly declining component of the cost is due to the
high-temperature (> 900 °C) processing required to form p-n junctions. In this thesis,
the replacement of the high-temperature p-n junction with a low-temperature amorphous
titanium dioxide (TiO<sub>2</sub>)/silicon heterojunction is investigated. The TiO<sub>2</sub>/Si
heterojunction forms an electron-selective, hole-blocking contact. A chemical vapor
deposition method using only one precursor is utilized, leading to a maximum deposition
condition of 100 °C. High-quality passivation of the TiO<sub>2</sub>/Si interface is achieved,
with a minimum surface recombination velocity of 28 cm/s. This passivated TiO<sub>2</sub> is
used in a double-sided PEDOT/n-Si/TiO<sub>2</sub> solar cell, demonstrating an open-circuit
voltage increase of 45 mV. Further, a heterojunction bipolar transistor (HBT) method
is developed to investigate the current mechanisms across the TiO<sub>2</sub>/p-Si heterojunction,
leading to the determination that 4nm of TiO<sub>2</sub> provides the optimal thickness.
And finally, an analytical model is developed to explain the current mechanisms observed
across the TiO<sub>2</sub>/Si interface. From this model, it is determined that once
ΔE<sub>V</sub> (TiO<sub>2</sub>/Si) is large enough (400 meV), the two key parameters are the Schottky
barrier height (resulting in band-bending in silicon) and the recombination velocity
at the TiO<sub>2</sub>/Si interface. Data corroborates this, indicating the hole-blocking mechanism
is due to band-bending induced by the unpinning of the Al/Si interface and
TiO<sub>2</sub> charge, as opposed to due to the TiO<sub>2</sub> valence band edge.
| Identifer | oai:union.ndltd.org:PROQUEST/oai:pqdtoai.proquest.com:10823434 |
| Date | 21 June 2018 |
| Creators | Jhaveri, Janam |
| Publisher | Princeton University |
| Source Sets | ProQuest.com |
| Language | English |
| Detected Language | English |
| Type | thesis |
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