E-Thesis 76 views 20 downloads
The Thermodynamic Limit of Indoor Photovoltaics / MAURA FITZSIMONS
Swansea University Author: MAURA FITZSIMONS
Abstract
Indoor Photovoltaic development stands between low-power devices such as the Internet of Things and their potential widespread roll out. Semiconductor material choice, of the active layer, has the potential to enhance indoor photovoltaic performance. To begin the early-stage research of indoor photo...
| Published: |
Swansea, Wales, UK
2023
|
|---|---|
| Institution: | Swansea University |
| Degree level: | Master of Research |
| Degree name: | MSc by Research |
| Supervisor: | Meredith, P; Armin, A |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa65873 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Abstract: |
Indoor Photovoltaic development stands between low-power devices such as the Internet of Things and their potential widespread roll out. Semiconductor material choice, of the active layer, has the potential to enhance indoor photovoltaic performance. To begin the early-stage research of indoor photovoltaic material choice, the thermodynamic compatibility of the material systems with the incident illumination spectrum was evaluated. While organic semiconductors present many advantages in the photovoltaic industry due to their low di-electric constants and cheap processibility over their respective inorganic counterparts, a standout advantage for use of organic semiconductors in indoor photovoltaic applications is their wider effective energy gaps. By adopting the principle of detailed balance and applying Shockley-Queisser limit calculations to pre-existing external quantum efficiency data and two chosen indoor lighting spectra, promising material systems were identified prior to fabrication and optimisation. As a result, predictions of two high-efficiency material systems were made and, in addition to a model system, were characterised in the remainder of this Thesis.In addition to the Shockley-Queisser analysis of existing material systems for characterisation under simulated indoor illumination conditions, theoretical limits, including radiative (Shockley-Queisser) and non-radiative (empirical models produced from the literature), were calculated for the two chosen light emitting diode radiation sources. From this analysis, it was evident that the optimal energy gap for an indoor photovoltaic system under these conditions was much wider than originally calculated for the scenario subject to solar illumination (1.14 eV). The optimal bandgap for the chosen light emitting diode source of 4000 K was equivalent to an effective energy gap of 1.89 eV, significantly higher than the energy gap that devices have been optimised towards historically, potentially capable of approximately 40% power conversion efficiency including non-radiative loss simulations at illuminances as low as 50 lux. Finally leading onto answering one of the aims of this Thesis; what is more important, thermodynamic compatibility or outperforming charge transport properties? Firstly, it can be considered that the EH-IDTBR and BTP-eC9 based devices are thermodynamically compatible and of above average charge transport properties. Therefore, with improvements to the short-circuit current, the thermodynamic compatibility could carry more weight in the optimisation of indoor organic photovoltaic devices.An additional investigation carried out through this Thesis is into the effect of shunt resistance on indoor organic photovoltaics. When observing both EH-IDTBR based systems, their varying shunt resistances (recorded via a dark characterisation process) present themselves significantly in the open-circuit voltage and fill factor dependence on light intensity. By performing these measurements, the incident illuminance at which the devices began to quickly deplete in performance was evaluated, therefore implying their importance.In summary, considering both the radiative and empirical non-radiative limits, the work presented in this Thesis provides valuable insight into the optimal effective energy gap for photovoltaic devices under two chosen model indoor illumination spectra. In addition, important evidence of the significant effect of shunt resistance on indoor photovoltaic device performance at low light intensities is presented, with conclusions that could make device selection more efficient for test under indoor characterisation. Finally, the importance of thermodynamic compatibility was emphasised. In combination, all of the aforementioned conclusions could potentially be used to aid the development of indoor organic photovoltaics. |
|---|---|
| Item Description: |
Part of this thesis has been redacted to protect personal information |
| Keywords: |
Thermodynamics, Photovoltaic, Indoor Photovoltaic, Shockley-Queisser Limit, Semiconductor, Organic Semiconductor, PBDB-T, EH-IDTBR, PM6 |
| College: |
Faculty of Science and Engineering |