Halide perovskite solar cells, with rapid efficiency improvements from ~10% to ~23% in 6 years, have attracted significant attention due to their remarkable performance, low processing cost and their potential to become a strong alternative candidate to silicon solar cells. Significant development has also been achieved in halide perovskite-based LEDs with EQE improved from below 1% to ~20% in less than 4 years. This remarkable progress can mainly be attributed to the optimisation of halide perovskite properties. This dissertation focuses on the correlation between optical and electrical properties of halide perovskites and their remarkable performance. Bandgap tunabilities of halide perovskites in blue to green regions through mixing Br-and Cl-and in near infra-red region by substituting Pb2+ with Sn2+ are demonstrated. The absorption and PL spectra are consistent with each other supporting the bandgap tunability. Corresponding EL spectra, which are consistent with their PL spectra, are also demonstrated for blue to green regions. Terahertz measurements coupled with PLQE and transient PL results reveal that the high carrier mobilities are the main reason behind the high efficiency of tin-rich samples. A novel perovskite-polymer-bulk heterostructure is introduced and studied comprehensively. Correlations between their optoelectronic properties and remarkable performance on timescales ranging from femtosecond to microsecond are presented. Transient optical spectroscopy reveals the energy transfer from 2D regions to 3D regions happens in 1 ps. The 20% EQE of the LEDs based in this structure is consistent with conventional thin-film optical models giving internal quantum efficiency of ~100%. This in agreement with near-unity PLQE value of the pristine emissive layer material and the dominant bimolecular recombination process observed in nanosecond-scale transient PL measurements. Two typical interfacial engineering methods to improve the quality of halide perovskite and device performance are then presented. Optimised NiOx is adopted to improve the anode interface. From transient photovoltaic measurements, we find the charge collection ability of NiOx is superior to that of PEDOT:PSS. This is also the main reason behind their better photovoltaic device performance. A unique anti-solvent treatment with additive modifies both the bulk and surfaces of halide perovskites and improves the device performance significantly. Transient PL and PLQE measurements demonstrate that non-radiative recombination pathways are significantly reduced.

Zinc oxide (ZnO) is a promising photoanode material which has been used in quantum dot-based depleted heterojunction solar cells. The specific influence of the defect chemistry of ZnO on its n-type conductivity remains a focus for research. This thesis presents results from a series of near-ambient pressure (NAP) XPS experiments (at The University of Manchester, UK), used to characterise surface adsorption of O2 and H2O on ZnO(10-10) surfaces in high pressure environments. Water dosing is shown to lead to surface hydroxylation and a change in the surface band bending consistent with an increase in the surface conductivity. Oxygen dosing is also observed to lead to the formation of surface species on the ZnO surface, revealing that ZnO is prone to hydroxylation even in oxygen-rich environments. The role of surface OH on influencing the transient surface photovoltage (SPV) of the ZnO(10-10) surface is probed through a series of time-resolved, pump-probe XPS experiments (at SOLEIL synchrotron, France). It is shown that increasing the degree of surface hydroxylation leads to a decrease in surface band bending, leading to longer-lived transient SPV. Other factors influencing the SPV dynamics are explored, such as the role of the oxygen vacancy concentration. The transient SPV decay lifetime is shown to increase with increasing oxygen vacancy concentration, consistent with the presence of persistent photoconductivity (PPC) in ZnO, mediated by oxygen vacancy-related hole traps. The influence of the concentration of thermally excited carriers in ZnO on the surface band bending is also described, showing that the equilibrium band bending and the surface photovoltage are both reduced at low temperature. It is shown that thermal excitation of carriers from the valence band of ZnO and from neutral oxygen vacancies have negligible influence on the magnitude of equilibrium band bending at the surface. The energy regime consistent with the observed temperature dependence is also consistent with a perturbed-host state 0.2 eV below the conduction band minimum. This meta-stable state is associated with doubly-ionised oxygen vacancies, that mediate the PPC in ZnO. However this does not rule out the contribution from other shallow donor levels such as those associated with hydrogen impurities. The influence of hydrogen on the SPV dynamics in ZnO is explored, through angle-resolved photoemission spectroscopy (ARPES) after implanting hydrogen atoms into the ZnO surface. H implantation is shown to lead to the formation of a 2D electron gas (2DEG) at the surface, consistent with an increase in conductivity at the surface large enough to change the nature of the space-charge region at the ZnO surface from depletion to accumulation.

abstract: In order to meet climate targets, the solar photovoltaic industry must increase photovoltaic (PV) deployment and cost competitiveness over its business-as-usual trajectory. This requires more efficient PV modules that use less expensive materials, and longer operational lifetime. The work presented here approaches this challenge with a novel metallization method for solar PV and electronic devices. This document outlines work completed to this end. Chapter 1 introduces the areas for cost reductions and improvements in efficiency to drive down the cost per watt of solar modules. Next, in Chapter 2, conventional and advanced metallization methods are reviewed, and our proposed solution of dispense printed reactive inks is introduced. Chapter 3 details a proof of concept study for reactive silver ink as front metallization for solar cells. Furthermore, Chapter 3 details characterization of the optical and electrical properties of reactive silver ink metallization, which is important to understanding the origins of problems related to metallization, enabling approaches to minimize power losses in full devices. Chapter 4 describes adhesion and specific contact resistance of reactive ink metallizations on silicon heterojunction solar cells. Chapter 5 compares performance of silicon heterojunction solar cells with front grids formed from reactive ink metallization and conventional, commercially available metallization. Performance and degradation throughout 1000 h of accelerated environmental exposure are described before detailing an isolated corrosion experiment for different silver-based metallizations. Finally, Chapter 6 summarizes the main contributions of this work. The major goal of this project is to evaluate potential of a new metallization technique –high-precision dispense printing of reactive inks–to become a high efficiency replacement for solar cell metallization through optical and electrical characterization, evaluation of durability and reliability, and commercialization research. Although this work primarily describes the application of reactive silver inks as front-metallization for silicon heterojunction solar cells, the work presented here provides a framework for evaluation of reactive inks as metallization for various solar cell architectures and electronic devices. / Dissertation/Thesis / Doctoral Dissertation Materials Science and Engineering 2019

Solar energy harvesting demands low-cost energy conversion in the infrared from 1 – 2 μm. However, solution-processed photovoltaic devices have remained relatively inefficient in this spectral region. Herein, lead sulfide colloidal nanocrystal quantum dots are used to facilitate efficient infrared power conversion. Solution-cast nanocrystal films are employed in a simple metal/semiconductor/metal architecture to produce a photovoltaic effect. It is shown that a Schottky barrier is induced, which is responsible for the charge separating action. Through optimization of chemical processes and device fabrication, the photovoltaic response is maximized. The infrared power conversion efficiency reaches 4.2%, which sets a new precedent for solution-processed photovoltaic cells. Furthermore, the devices exhibit efficient broadband solar power conversion and show promise for multijunction cell architectures. Carrier drift through a large depletion region near the Schottky contact is determined to be the dominant transport mechanism.

Aluminum Doped Zinc Oxide (AZO) produced by radio frequency (RF) magnetron sputtering is thought to be the prospective replacement of the de facto standard indium tin oxide (ITO) anode in organic solar cells. In order to achieve a proper resistivity and transmittance of AZO thin film compared to ITO, a systematic study was done to optimize the sputtering conditions. In this work, two primary parameters: target-substrate distance and sputtering power, were optimized, and a optimized film thickness was determined. A poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) bulk-heterojunction organic solar cell was fabricated based on the optimized parameters and the power conversion efficiency reached 0.83%. A theoretical analysis is given to explain the optimization process. This work provides a clear pathway to substitute AZO for ITO in organic solar cells for future mass production.

Aluminum Doped Zinc Oxide (AZO) produced by radio frequency (RF) magnetron sputtering is thought to be the prospective replacement of the de facto standard indium tin oxide (ITO) anode in organic solar cells. In order to achieve a proper resistivity and transmittance of AZO thin film compared to ITO, a systematic study was done to optimize the sputtering conditions. In this work, two primary parameters: target-substrate distance and sputtering power, were optimized, and a optimized film thickness was determined. A poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) bulk-heterojunction organic solar cell was fabricated based on the optimized parameters and the power conversion efficiency reached 0.83%. A theoretical analysis is given to explain the optimization process. This work provides a clear pathway to substitute AZO for ITO in organic solar cells for future mass production.

The report is focused on the implementation of a data acquisition system that will be used for measuring different parameters which are needed in solar panel behavior analysis. To accomplish the DAQ system a DAQ board has been designed and implemented. This DAQ board acquires measured climatic parameters that affect the PV module behavior and voltage and current of a PV module. The DAQ board may take measurements of multiple analog and digital signals that come from various sensors including solar radiation, temperature, wind sensors and other measurement devices. The DAQ board may also output analog signals for controlling other devices. The DAQ board is the basic part of the DAQ system and several of them can be connected via a single communication bus (RS485). A unique slave ID can be assigned to each DAQ board on the communication bus, which allows the control of all boards via a GUI application installed on a master computer. Therefore, the DAQ system can be used for monitoring a PV module installation as well as logging the measured data in a data storage server. This report outlines the details of the DAQ system design which are helpful in utilizing or upgrading this system. These details also include programming of DAQ board and implementation of MODBUS communication protocol within the DAQ system.

Solar energy harvesting demands low-cost energy conversion in the infrared from 1 – 2 μm. However, solution-processed photovoltaic devices have remained relatively inefficient in this spectral region. Herein, lead sulfide colloidal nanocrystal quantum dots are used to facilitate efficient infrared power conversion. Solution-cast nanocrystal films are employed in a simple metal/semiconductor/metal architecture to produce a photovoltaic effect. It is shown that a Schottky barrier is induced, which is responsible for the charge separating action. Through optimization of chemical processes and device fabrication, the photovoltaic response is maximized. The infrared power conversion efficiency reaches 4.2%, which sets a new precedent for solution-processed photovoltaic cells. Furthermore, the devices exhibit efficient broadband solar power conversion and show promise for multijunction cell architectures. Carrier drift through a large depletion region near the Schottky contact is determined to be the dominant transport mechanism.

Increasing  environmental  pressure  makes  it  significantly  important  to  improve  the share  of  renewable  energy  source  in  terms  of  sustainable  development.  Photovoltaic  (PV)  cells are one of the most promising technologies at present for utilizing solar radiation. However,  the large  scale  of  PV  penetration  with  its  character  of  intermittency  may  cause  problems  for  the power system and requires a more complex power system control. Self-consumption is a feasible solution to reduce the negative impact of PV on the power system. On the other hand, Plugged-in electric vehicle which could get charged by the electricity from the grid is a potential load for the general household in the future since the introduction of electric vehicles (EVs) is critical for building  a  fossil-fuel  independent  transportation.  The  aim  of  the  project  is  to  investigate  the effect on the power consumption profile when adding PV generation and electric vehicle load, as well  as  whether  the  introduction  of  electric  vehicle  will  help  improve  the  matching  between electricity consumption and PV generation. This study is done on both an individual household scale and a national scale. Conclusion from the simulation is that home-charged EV accounts for a  great  deal  of  energy  consumption  for  a  single  household  and  it  could  improve  the  national energy  consumption  to  some  extent  if  largely  introduced  into  the  power  system.  In  addition, Home-charged EV without strategic control does not improve self-consumption of PV either for a single household or on a national scale. / <p></p><p></p>

The increase in the consumption of energy year after year emphasizes the importance of power production by photovoltaic (PV) systems. Despite an increase in the use of PV systems, accurate solar power [kWh] daily harvest predicting data are not readily available. Accurate predicted solar power data is necessary because the data is helpful to designers who need to optimally size a PV panel before installation. Moreover, accurately predicted max dc power can indicate whether the PV panel is operating efficiently and economically or not. This thesis develops an approach to predict max solar power based on a Linear Regression model. The approach, which ia a simple regression was implemented using measured data on a response variable, a max solar power (Pmax), and predictor variables such as Global Horizontal (GH), Plane of Array (PA), Short Circuit Current (Isc), Open Circuit Voltage (Voc), and Panel Temperature (Temp). The statistical results of the linear regression model produced reasonable values which agreed with those of the measured data from the solar panel. / text