Novel paradigms for resonance energy transfer mediated hybrid photovoltaic devices

This work focuses on the utilisation of quantum dots (QDs) and resonance energy transfer to enhance the properties of existing photovoltaic technologies. Time-resolved spectroscopy is used to demonstrate that lead sulphide (PbS) QDs could be used to enhance the absorptivity of silicon solar cells. In this scheme, QDs deposited on the solar cell act as absorber, while the photogenerated excitons are transferred to the underlying silicon to contribute to the photocurrent. QD hybridization is also demonstrated in InGaP solar cells. In this case, the QDs are used to mitigate the poor utilisation of the energy absorbed in the AlInP window layer. Excitons generated in this layer are non-radiatively transferred to the QDs, which emit photons below the AlInP band-gap to generate carriers close to the depletion region of the p-n junction. The overall performance of the solar cell is found to be significantly improved after hybridization, with a large 14.6% relative and 2% absolute enhancement of the photon conversion efficiency. Finally, the integration of QDs into thin film Cu(In,Ga)Se2 (CIGS) solar cells is investigated. The deposition of a non-uniform layer of QD aggregates in close proximity to the heterojunction is found to provide a 10.9% relative enhancement of the photon conversion efficiency. Enhancements of the external quantum efficiency in both the blue and near-IR ranges are attributed respectively to radiative luminescent down-shifting from the QDs and to scattering on QD aggregates. Throughout this thesis, evidence is provided that placing efficient nanocrystaline emitters near (&lt

Size- and temperature-dependent carrier dynamics in oleic acid capped PbS quantum dots

In this work, we investigate the temperature dependence of the photoluminescence decay and integrated photoluminescence of oleic acid capped PbS quantum dots with diameters ranging from 2.3 to 3.5 nm over a broad temperature range (6–290 K). All the investigated samples exhibit similar behavior, consisting of three different temperature regimes. The low-temperature regime (<180 K) is characterized by an increase in the average decay rate and a decrease in integrated photoluminescence. The intermediate regime (∼180–250 K) is described by an enhancement in the photoluminescence intensity and a decrease in the average decay rate. The high-temperature regime (>250 K) is governed by quenched photoluminescence intensity and acceleration in the average lifetimes. We propose a three-level system, composed of bright, dark, and surface states, which describes the observed photoluminescence dynamics of oleic acid capped PbS QDs

Hybrid photonic crystal LED renders 123% color conversion effective quantum yield - Raw data

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Efficient light harvesting in hybrid quantum dot-interdigitated back contact solar cells via resonant energy transfer and luminescent downshifting

In this paper, we propose a hybrid quantum dot (QD)/solar cell configuration to improve performance of interdigitated back contact (IBC) silicon solar cells, resulting in 39.5% relative boost in the short-circuit current (JSC) through efficient utilisation of resonant energy transfer (RET) and luminescent downshifting (LDS). A uniform layer of CdSe1−xSx/ZnS quantum dots is deposited onto the AlOx surface passivation layer of the IBC solar cell. QD hybridization is found to cause a broadband improvement in the solar cell external quantum efficiency. Enhancement over the QD absorption wavelength range is shown to result from LDS. This is confirmed by significant boosts in the solar cell internal quantum efficiency (IQE) due to the presence of QDs. Enhancement over the red and near-infrared spectral range is shown to result from the anti-reflection properties of the QD layer coating. A study on the effect of QD layer thickness on solar cell performance was performed and an optimised QD layer thickness was determined. Time-resolved photoluminescence (TRPL) spectroscopy was used to investigate the photoluminescence dynamics of the QD layer as a function of AlOx spacer layer thickness. RET can be evoked between the QD and Si layers for very thin AlOx spacer layers, with RET efficiencies of up to 15%. In the conventional LDS architecture, down-converters are deposited on the surface of an optimised anti-reflection layer, providing relatively narrowband enhancement, whereas the QDs in our hybrid architecture provide optical enhancement over the broadband wavelength range, by simultaneously utilising LDS, RET-mediated carrier injection, and antireflection effects, resulting in up to 40% improvement in the power conversion efficiency (PCE). Low-cost synthesis of QDs and simple device integration provide a cost-effective solution for boosting solar cell performance