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Doctor of Philosophy / Department of Chemistry / Jun Li / Solar energy as a sustainable resource is a promising alternative to fossil fuels to solve the tremendous global energy crisis. Development of three generation of solar cells has promoted the best sunlight to electricity conversion efficiency above 40%. However, the most efficient solar cells rely on expensive nonsustainable raw materials in device fabrication. There is a trend to develop cost-effective biophotovoltaics that combines natural photosynthetic systems into artificial energy conversion devices such as dye sensitized solar cells (DSSCs). In this research, a model system employs natural extract light-harvesting complex II (LHCII) as a light-absorbing sensitizer to interface with semiconductive TiO₂ and plasmonic nanoparticles in DSSCs. The goal of this research is to understand the fundamental photon capture, energy transfer and charge separation processes of photosynthetic pigment-protein complexes along with improving biophotovoltaic performance based on this model system through tailoring engineering of TiO₂ nanostructures, attaching of the complexes, and incorporating plasmonic enhancement. The first study reports a novel approach to linking the spectroscopic properties of nanostructured LHCII with the photovoltaic performance of LHCII-sensitized solar cells (LSSCs). The aggregation allowed reorganization between individual trimers which dramatically increased the photocurrent, correlating well with the formation of charge-transfer (CT) states observed by absorption and fluorescence spectroscopy. The assembled solar cells demonstrated remarkable stability in both aqueous buffer and acetonitrile electrolytes over 30 days after LHCII being electrostatically immobilized on amine-functionalized TiO₂ surface. The motivation of the second study is to get insights into the plasmonic effects on the nature of energy/charge transfer processes at the interface of photosynthetic protein complexes and artificial photovoltaic materials. Three types of core-shell (metal@TiO₂) plasmonic nanoparticles (PNPs) were conjugated with LHCII trimers to form hybrid systems and incorporated into a DSSC platform built on a unique open three-dimensional (3D) photoanode consisting of TiO₂ nanotrees. Enhanced photon harvesting capability, more efficient energy transfer and charge separation at the LHCII/TiO₂ interface were confirmed in the LHCII-PNP hybrids, as revealed by spectroscopic and photovoltaic measurements, demonstrating that interfacing photosynthesis systems with specific artificial materials is a promising approach for high-performance biosolar cells. Furthermore, the final study reveals the mechanism of hot electron injection by employing a mesoporous core-shell (Au@TiO₂) network as a bridge material on a micro-gap electrode to conduct electricity under illumination and comparing the photoconductance to the photovolatic properties of the same material as photoanodes in DSSCs. Based on the correlation of the enhancements in photoconductance and photovoltaics, the contribution of hot electrons was deconvoluted from the plasmonic near-field effects.

This research investigated the effect of electron injection in III-Nitrides. The combination of electron beam induced current and cathodoluminescence measurements was used to understand the impact of electron injection on the minority carrier transport and optical properties. In addition, the application of the electron injection effect in optoelectronic devices was investigated. The impact of electron injection on the minority carrier diffusion length was studied at various temperatures in Mg-doped p-GaN, p-Al[subscript x]Ga[subscript 1-x]N, and p-Al[subscript x]Ga[subscript 1-x] N/GaN superlattices. It was found that Lsubscript n] experienced a multi-fold linear increase and that the rate of change of L[subscript n] decreased exponentially with increasing temperature. The effect was attributed to a temperature-activated release of the electrons, which were trapped by the Mg levels. The activation energies, E[subscript a], for the electron injection effect in the Mg-doped (Al)GaN samples were found to range from 178 to 267 meV, which is close to the thermal ionization energy of the Mg acceptor. The E[subscript a] observed for Al[subscript 0.15]Ga[subscript 0.85]N and Al[subscript 0.2]Ga[subscript 0.8]N was consistent with the deepening of the Mg acceptor level due to the incorporation of Al into the GaN lattice. The E[subscript a] in the homogeneously doped Al[subscript 0.2]Ga[subscript 0.8]N/GaN superlattice indicates that the main contribution to the electron injection effect comes from the capture of injected electrons by the wells (GaN). The electron injection effect was successfully applied to GaN doped with an impurity (Mn) other than Mg. Electron injection into Mn-doped GaN resulted in a multi-fold increase of the L[subscript n] and a pronounced decrease in the band-to-band cathodoluminescence intensity. The E[subscript a] due to the electron injection effect was estimated from temperature-dependent cathodoluminescence measurements to be 360 meV. The decrease in the band-to-band cathodoluminescence is consistent with an increase in L[subscript n] and these results are attributed to an increase in the minority carrier lifetime due to the trapping of injected electrons by the Mn levels. A forward bias was applied to inject electrons into commercially built p-i-n and Schottky barrier photodetectors. Up to an order of magnitude increase in the peak (360 nm) responsivity was observed. The enhanced photoresponse lasted for over four weeks and was attributed to an electron injection-induced increase of L[subscript n] and the lifetime.

Interfaces between semiconductors and adsorbed molecules form a central area of research in surface science, occurring in many different contexts. One such application is the so-called Dye-Sensitized Solar Cell (DSSC) where the nanostructured dye-semiconductor interface is of special interest, as this is where the most important ultrafast electron transfer process takes place. In this thesis, structural and electronic aspects of these interfaces have been studied theoretically using quantum chemical computations applied to realistic dye-semiconductor systems. Periodic boundary conditions and large cluster models have been employed together with hybrid HF-DFT functionals in the modeling of nanostructured titanium dioxide. A study of the adsorption of a pyridine molecule via phosphonic and carboxylic acid anchor groups to an anatase (101) surface showed that the choice of anchor group affects the strength of the bindings as well as the electronic interaction at the dye-TiO2 interface. The calculated interfacial electronic coupling was found to be stronger for carboxylic acid than for phosphonic acid, while phosphonic acid binds significantly stronger than carboxylic acid to the TiO2 surface. Atomistic and electronic structure of realistic dye-semiconductor interfaces were reported for RuII-bis-terpyridine dyes on a large anatase TiO2 cluster and perylene dyes on a periodic rutile (110) TiO2 surface. The results show strong influence of anchor and inserted spacer groups on adsorption and electronic properties. Also in these cases, the phosphonic acid anchor group was found to bind the dyes significantly stronger to the surface than the carboxylic acid anchor, while the interfacial electronic coupling was stronger for the carboxylic anchor. The estimated electron injection times were twice as fast for the carboxylic anchor compared to the phosphonic anchor. Moreover, the electronic coupling was affected by the choice of spacer group, where unsaturated spacer groups were found to mediate electron transfer more efficiently than saturated ones.

Grätzel cells or Dye-Sensitized Solar Cells (DSSCs) are considered one of the most promising methods to convert the sun's energy into electricity due to their low cost and simple technology of production. The Grätzel cell is based on a photosensitizer adsorbed on a low band gap semiconductor. The photosensitizer can be a metal complex or an organic dye. Organic dyes can be produced on a large scale resulting in cheaper dyes than complexes based on rare elements. However, the performance of Grätzel cells based on metal-free, organic dyes is not high enough yet. The dye's performance depends primarily on the electron dynamics. The electron dynamics in Grätzel cells includes electron injection, recombination, and regeneration. Different deactivation processes affect the electron dynamics and the cells’ performance. In this thesis, the electron dynamics was explored by various time-resolved spectroscopic techniques, namely time-correlated single photon counting, streak camera, and femtosecond transient absorption. Using these techniques, new deactivation processes for organic dyes used in DSSCs were uncovered. These processes include photoisomerization, and quenching through complexation with the electrolyte. These deactivation processes affect the performance of organic dyes in Grätzel cells, and should be avoided. For instance, the photoisomerization can compete with the electron injection and produce isomers with unknown performance. Photoisomerization as a general phenomenon in DSSC dyes has not been shown before, but is shown to occur in several organic dyes, among them D149, D102, L0 and L0Br. In addition, D149 forms ground state complexes with the standard iodide/triiodide electrolyte, which directly affect the electron dynamics on TiO2. Also, new dyes were designed with the aim of using ferrocene(s) as intramolecular regenerators, and their dynamics was studied by transient absorption. This thesis provides deeper insights into some deactivation processes of organic dyes used in DSSCs. New rules for the design of organic dyes, based on these insights, can further improve the efficiency of DSSCs.

Semiconductor nanocrystals, also referred to as quantum dots (QDs), have been the focus of great scientific and technological efforts in solar cells, as a result of their advantages of low-cost, photostability, high molar extinction coefficients and size-dependent optical properties. Due to the multi-electron generation effect, the theoretically maximum efficiency of quantum dots-sensitized solar cells (QDSCs) is as high as 44%, which is much higher than that of dye-sensitized solar cells (DSCs). Thus QDSCs have a clear potential to overtake the efficiency of all other kinds of solar cells. In recent years, the efficiency of QDSCs has been improved very quickly to around 5%. It is however still much lower than that of DSCs. The low efficiency is mostly caused by the high electron loss between electrolyte and electrodes and the lack of an efficient electrolyte. In this thesis, we have been working to enhance the performance of QDSCs with II-VI group nanocrystals by increasing the electron injection efficiency from QDs to TiO2 and developing new redox couples in electrolyte. To increase the electron injection, firstly, colloidal ZnSe/CdS type-II QDs were synthesized and applied for QDSCs for the first time, whose photoelectron and photohole are located on CdS shell and ZnSe core, respectively. The spatial separation between photoelectron and photohole can effectively enhance the charge extraction efficiency, facilitating electron injection, and also effectively expand the absorption spectrum. All these characteristics contribute to the high photon to current conversion efficiency. Furthermore, a comparison between the performances of ZnSe/CdS and CdS/ZnSe QDs shows that the electron distribution is important for the electron injection of the QDs in QDSCs. Secondly, colloidal CdS/CdSe quantum rods (QRs) were applied to a quantum rod-sensitized solar cell (QRSCs) that showed a higher electron injection efficiency than analogous QDSCs. It is concluded that reducing the carrier confinement dimensions of nanocrystals can improve electron injection efficiency of nanocrystal sensitized solar cells. In this thesis, two types of organic electrolytes based McMT-/BMT and TMTU/TMTU-TFO were used for QDSCs. By reducing the charge recombination between the electrolyte and counter electrode, fill factor (FF) of these QDSCs was significantly improved. At the same time, the photovoltages of the QDSCs were remarkably increased. As a result, the overall conversion efficiency of QDSCs based on the new electrolytes was much higher than that with a commonly used inorganic electrolyte. In addition, CdS QDSCs on NiO photoelectrode were studied which shows a n-type photovoltaic performance. This performance is attributed to the formation of a thin Cd metal film before CdS QDs formation on NiO. Since the CB edge of CdS sits between the Fermi level and the CB edge of Cd metal, a much strong electron transfer between Cd and CdS QD is obtained, resulting in the observed n-type photovoltaic performance of these CdS/NiO QDSCs. / QC 20120425

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Τα φωτοβολταϊκά στοιχεία με ευαισθητοποίηση χρωστικής (Dye Sensitized Solar Cells, DSSCs) κίνησαν το ενδιαφέρον της επιστημονικής κοινότητας ύστερα από την πρωτότυπη δημοσίευση του 1991 των Grätzel και O' Regan. Προτάθηκαν ως μία φθηνή εναλλακτική λύση σε σύγκριση με τα συμβατικά ηλιακά στοιχεία από άμορφο πυρίτιο (amorphous silicon). Οι κύριοι παράγοντες που οδήγησαν την επιστημονική κοινότητα να στραφεί προς αυτή την κατεύθυνση ήταν η ευκολία σύνθεσης των χρωστικών με σχετικά απλές χημικές διαδικασίες και η λειτουργία των νέων αυτών φωτοβολταϊκών στοιχείων υπό συνθήκες διάχυτου φωτός. Γενικά, ένα τέτοιο φωτοβολταϊκό στοιχείο αποτελείται από μία φωτοάνοδο (photoanode), ένα πορώδες υπόστρωμα από ημιαγώγιμο οξείδιο μετάλλου (metal oxide semiconducting film), μία χρωστική που χρησιμοποιείται ως φωτοευαισθητοποιητής (sensitizer), έναν ηλεκτρολύτη (electrolyte) και ένα αντιηλεκτρόδιο (counter electrode), το οποίο, συνήθως, επικαλύπτεται με ένα λεπτό στρώμα από πλατίνα (Pt). Η κύρια διεργασία που λαμβάνει μέρος σε ένα DSSC, μετά από την απορρόφηση φωτός, είναι μία διεπιφανειακή μεταφορά φορτίου (interfacial electron transfer IET) από την ηλεκτρονιακά διεγερμένη στάθμη της χρωστικής προς τη ζώνη αγωγιμότητας του ημιαγωγού. Η χρονική της διάρκεια είναι της τάξεως των μερικών εκατοντάδων fs και κατατάσσεται στα υπερταχέα φαινόμενα. Ο όρος που έχει επικρατήσει, για τη διεργασία αυτή στα DSSCs, είναι έκχυση ηλεκτρονίων (electron injection) και χρησιμοποιείται στην παρούσα διπλωματική εργασία. Η τεχνική της φασματοσκοπίας φθορισμού χρονικής ανάλυσης με παλμούς διάρκειας μερικών δεκάδων fs, αποτελεί μία από τις πιο αξιόπιστες και άμεσες τεχνικές για την καλύτερη δυνατή καταγραφή υπερταχέων φαινομένων, όπως η έκχυση ηλεκτρονίων. Σκοπός της παρούσας διπλωματικής εργασίας είναι η μελέτη της έκχυσης ηλεκτρονίων με τη χρήση δύο νέων οργανικών χρωστικών, της μορφής D-π-A, ως φωτοευαισθητοποιητές σε DSSCs με την τεχνική αυτή.Στο πρώτο κεφάλαιο πραγματοποιείται μία γενική επισκόπηση των βασικών αρχών που διέπουν τα φωτοβολταϊκά στοιχεία με ευαισθητοποίηση χρωστικής. Αρχικά, γίνεται αναφορά στα μέρη που αποτελούν ένα τέτοιο φωτοβολταϊκό στοιχείο και ακολούθως στα υλικά και στις διεργασίες οι οποίες συμμετέχουν σε ένα ολοκληρωμένο DSSC.Στο δεύτερο κεφάλαιο επιχειρείται, στο πρώτο σκέλος, μία γενική ανασκόπηση της θεωρίας του Markus για τη μεταφορά των ηλεκτρονίων (Markus Theory). Έπειτα, πραγματοποιείται μία αναλυτική επισκόπηση της δυναμικής και κινηματικής των διεργασιών που συντελούνται στα DSSCs. Συνεχίζοντας στο τρίτο κεφάλαιο, παρουσιάζονται πληροφορίες σχετικές με τα υποστρώματα και τις χρωστικές που χρησιμοποιούνται στα DSSCs. Το κεφάλαιο επικεντρώνεται στην περιγραφή των υποστρωμάτων TiO2 και ΖnO, τα οποία αποτελούν τα κύρια υποστρώματα που χρησιμοποιούνται στα DSSCs. Στο δεύτερο σκέλος του κεφαλαίου, πραγματοποιείται αναφορά στις ιδιότητες που οφείλουν να πληρούν οι χρωστικές, για τη χρήση τους στα DSSCs, καθώς και εκτενής ανασκόπηση των χρωστικών, οι οποίες έχουν χρησιμοποιηθεί, μέχρι σήμερα, ως φωτοευαισθητοποιητές. Στο τέταρτο κεφάλαιο παρουσιάζονται οι μηχανισμοί που συμμετέχουν κατά την αποδιέγερση ενός οργανικού μορίου και οι χρονικές κλίμακες, που αυτοί εμφανίζονται (διάγραμμα Jablonski). Επίσης, γίνεται αναφορά στις πληροφορίες που εξάγονται από τα φάσματα σταθερής κατάστασης (steady state spectra) και χρονικής ανάλυσης (time-resolved spectra), καθώς και η μεταξύ τους σύγκριση. Στο πέμπτο κεφάλαιο πραγματοποιείται μία αναλυτική περιγραφή της πειραματικής διάταξης, η οποία χρησιμοποιήθηκε για την εξαγωγή των πειραματικών δεδομένων. Τέλος, στα τελευταία δύο κεφάλαια (πέμπτο και έκτο) περιγράφεται, στο πρώτο, ο φωτοφυσικός χαρακτηρισμός των δύο νέων οργανικών χρωστικών, ΜΖ-173 και ΜΖ-175, της δομής D-π-Α, σε διάλυμα THF και σε στερεό υπόστρωμα TiO2 αντίστοιχα, το οποίο χρησιμοποιήθηκε ως το υπόστρωμα προσρόφησης των χρωστικών. Ακολούθως, μελετήθηκε η δυναμική και η απόδοση της έκχυσης των ηλεκτρονίων από τις χρωστικές αυτές προς το ημιαγώγιμο υπόστρωμα TiO2, με χρήση της τεχνικής της φασματοσκοπίας χρονικής ανάλυσης φθορισμού με παλμούς διάρκειας μερικών δεκάδων fs (femtosecond time resolved fluorescence spectroscopy). Ως δείγμα αναφοράς, για την εύρεση της απόδοσης της έκχυσης των ηλεκτρονίων στη ζώνη αγωγιμότητας του ημιαγωγού, χρησιμοποιήθηκε νανοκρυσταλλικό υπόστρωμα Al2O3. Τέλος, πραγματοποιήθηκε η μελέτη της δυναμικής της έκχυσης των ηλεκτρονίων με τη χρήση του μορίου CDCA, ως συνπροσροφητή στην επιφάνεια των υποστρωμάτων TiO2 και Al2O3, μαζί με χρωστική ΜΖ-173, σε διάφορες συγκεντρώσεις. Αυτή η μελέτη έγινε με σκοπό τη μείωση της συσσωμάτωσης των μορίων της χρωστικής, αφού το μόριο CDCA έχει την ιδιότητα, λόγω της δομής του, να κρατά σε απόσταση τα μόρια της χρωστικής. / Dye-sensitized solar cells (DSSCs) have attracted great scientific interest after the first demonstration of Grätzel and O’Regan in 1991. They were proposed as low cost alternatives to the conventional amorphous silicon solar cells. The key factors which led the scientific community to this direction are the simplicity of their fabrication procedures with mild chemical processes and their operation under ambient conditions of diffused light. Generally, a DSSC consists of a photoanode, a nanostructured metal oxide semiconducting film, a dye sensitizer, an electrolyte and a counter electrode which is usually coated with Pt. The fundamental process that takes place in a DSSC, after the absorption of a photon by the dye, is an interfacial electron transfer (IET) from the dye’s electronically excited state to the semiconductor’s conduction band (CB), taking place within a few hundred femtoseconds. The term which is generally used for this process in DSSCs is electron injection. Ultrafast fluorescence upconversion spectroscopy is one of the most precise and direct techniques for the study and interpretation of such phenomena. The main subject of this master thesis is the presentation of two novel synthesized organic dyes with D-π-A structure and their study as photosensitizers for DSSCs. It is focused on the photophycical properties of these two dyes in solution and on titanium dioxide (TiO2) substrate, which is used as the metal oxide semiconducting film, and especially on the dynamics of electron injection process from the dye’s excited state to the conduction band of the TiO2 with the aforementioned technique. Finally, the electron injection dynamics of one of dyes with coadsorption of co-adsorbers also investigated. This type of molecules can decrease the amount of aggregates penetrating among the dye molecules but on the same time they cause a decrease of the total amount of the adsorbed dye molecules.

Abstract: When noble metals particles are synthesized with progressively smaller dimensions, strikingly novel optical properties arise. For nanoscale particles, collective disturbances of the electron density known as localized surface plasmons resonances can arise, and these resonances are utilized in a variety of applications ranging from surface-enhanced molecular spectroscopy and sensing to photothermal cancer therapy to plasmon-driven photochemistry. Central to all of these studies is the plasmon’s remarkable ability to process light, capturing and converting it into intense near fields, heat, and even energetic carriers at the nanoscale. In the past decade, we have witnessed major advances in plasmonics which is directly linked with the much broader field of (colloidal) nanotechnology. These breakthroughs span from plasmon lasing and waveguides, plasmonic photochemistry and solar cells to active plasmonics, plasmonics nanocomposites and semiconductor plasmons. All the above-mentioned phenomena rely on precise spatial placement and distinct control over the dimensions and orientation of the individual plasmonic building blocks within complex one-, two- or three-dimensional complex arrangements. For the nanofabrication of metal nanostructures at surfaces, most often lithographic approaches, e.g. e-beam lithography or ion-beam milling are generally applied, due to their versatility and precision. However, these techniques come along with several drawbacks such as limited scalability, limited resolution, limited compatibility with silicon manufacturing techniques, damping effects due to the polycrystalline nature of the metal nanostructures and low sample throughput. Thus, there is a great demand for alternative approaches for the fabrication of metal nanostructures to overcome the above-mentioned limitations. But why colloids? True three-dimensionality, lower damping, high quality modes due to mono-dispersity, and the absence of grain boundaries make the colloidal assembly an especially competitive method for high quality large-scale fabrication. On top of that, colloids provide a versatile platform in terms of size, shape, composition and surface modification and dispersion media. 540The combination of directed self-assembly and laser interference lithography is a versatile admixture of bottom-up and top-down approaches that represents a compelling alternative to commonly used nanofabrication methods. The objective of this thesis is to focus on large area fabrication of emergent spectroscopic properties with high structural and optical quality via colloidal self-assembly. We focus on synergy between optical and plasmonic effects such as: (i) coupling between localized surface plasmon resonance and Bragg diffraction leading to surface lattice resonance; (ii) strong light matter interaction between guided mode resonance and collective plasmonic chain modes leading to hybrid guided plasmon modes, which can further be used to boost the hot-electron efficiency in a semiconducting material; (iii) similarly, bilayer nanoparticle chains leading to chiro-optical effects. Following this scope, this thesis introduces a real-time tuning of such exclusive plasmonic-photonic (hybrid) modes via flexible template fabrication. Mechanical stimuli such as tensile strain facilitate the dynamic tuning of surface lattice resonance and chiro-optical effects respectively. This expands the scope to curb the rigidity in optical systems and ease the integration of such systems with flexible electronics or circuits.:Contents Abstract Kurzfassung Abbreviations 1. Introduction and scope of the thesis 1.1. Introduction 1.1.1. Classical optics concepts 1.1.2. Top down fabrication methods and their challenges 1.1.3. Template-assisted self-assembly 1.1.4. Functional colloidal surface assemblies 1.2. Scope of the thesis 2. Results and Discussion 2.1. Mechanotunable Surface Lattice Resonances in the Visible Optical Range by Soft Lithography Templates and Directed Self-Assembly 2.1.1. Fabrication of flexible 2D plasmonic lattice 2.1.2. Investigation of the influence of particle size distribution on SLR quality 2.1.3. Band diagram analysis of 2D plasmonic lattice 2.1.4. Strain induced tuning of SLR 2.1.5. SEM and force transfer analysis in 2D plasmonic lattice under various strain 2.2. Hybridized Guided-Mode Resonances via Colloidal Plasmonic Self-Assembled Grating 2.2.1. Fabrication of hybrid opto-plasmonic structure via template assisted self-assembly 2.2.2. Comparison of optical band diagram of three (plasmonic, photonic and hybrid) different structures in TE and TM modes 2.2.3. Simulative comparison of optical properties of hybrid opto-plasmonic NP chains with a grating of metallic gold bars 2.2.4. Effect of cover index variation with water as a cover medium 2.3. Hot electron generation via guided hybrid modes 2.3.1. Fabrication of the hybrid GMR structure via LIL and lift-off process 2.3.2. Spectroscopic and simulative analysis of hybrid opto-plasmonic structures of different periodicities 2.3.3. Comparative study of photocurrent generation in different plasmonic structures 2.3.4. Polarization dependent response at higher wavelength 2.3.5. Directed self-assembly of gold nanoparticles within grating channels of a dielectric GMR structure supported by titanium dioxide film 2.4. Active Chiral Plasmonics Based on Geometrical Reconfiguration 2.4.1. Chiral 3D assemblies by macroscopic stacking of achiral chain substrates 3. Conclusion 4. Zusammenfassung 5. Bibliography 6. Appendix 6.1. laser interference lithography 6.2. Soft molding 6.3. Determine fill factor of plasmonic lattice 6.4. 2D plasmonic lattice of Au_BSA under strain 6.5. Characterizing order inside a 2D lattice 6.6. Template-assisted colloidal self-assembly 6.7. Out of plane lattice resonance in 1D and 2D lattices 6.8. E-Field distribution at out of plane SLR mode for 1D lattices of various periodicity with AOI 20° 6.9. Refractive index of PDMS and UV-PDMS 6.10. Refractive index measurement for sensing 6.11. Optical constants of TiO2, ma-N 405 photoresist and glass substrate measured from spectroscopic ellipsometry Acknowledgement/ Danksagung Erklärung & Versicherung List of Publications

This thesis presents a mathematical model of the nanoporous anode within a dyesensitised solar cell (DSC). The main purpose of this work is to investigate interfacial charge transfer and charge transport within the porous anode of the DSC under both illuminated and non-illuminated conditions. Within the porous anode we consider many of the charge transfer reactions associated with the electrolyte species, adsorbed dye molecules and semiconductor electrons at the semiconductor-dye- electrolyte interface. Each reaction at this interface is modelled explicitly via an electrochemical equation, resulting in an interfacial model that consists of a coupled system of non-linear algebraic equations. We develop a general model framework for charge transfer at the semiconductor-dye-electrolyte interface and simplify this framework to produce a model based on the available interfacial kinetic data. We account for the charge transport mechanisms within the porous semiconductor and the electrolyte filled pores that constitute the anode of the DSC, through a one- dimensional model developed under steady-state conditions. The governing transport equations account for the diffusion and migration of charge species within the porous anode. The transport model consists of a coupled system of non-linear differential equations, and is coupled to the interfacial model via reaction terms within the mass-flux balance equations. An equivalent circuit model is developed to account for those components of the DSC not explicitly included in the mathematical model of the anode. To obtain solutions for our DSC mathematical model we develop code in FORTRAN for the numerical simulation of the governing equations. We additionally employ regular perturbation analysis to obtain analytic approximations to the solutions of the interfacial charge transfer model. These approximations facilitate a reduction in computation time for the coupled mathematical model with no significant loss of accuracy. To obtain predictions of the current generated by the cell we source kinetic and transport parameter values from the literature and from experimental measurements associated with the DSC commissioned for this study. The model solutions we obtain with these values correspond very favourably with experimental data measured from standard DSC configurations consisting of titanium dioxide porous films with iodide/triiodide redox couples within the electrolyte. The mathematical model within this thesis enables thorough investigation of the interfacial reactions and charge transport within the DSC.We investigate the effects of modified cell configurations on the efficiency of the cell by varying associated parameter values in our model. We find, given our model and the DSC configuration investigated, that the efficiency of the DSC is improved with increasing electron diffusion, decreasing internal resistances and with decreasing dark current. We conclude that transport within the electrolyte, as described by the model, appears to have no limiting effect on the current predicted by the model until large positive voltages. Additionally, we observe that the ultrafast injection from the excited dye molecules limits the interfacial reactions that affect the DSC current.