Academic literature on the topic 'Dye-sensitized Solar Cells (DSSCs)'

ABSTRACT Background Solar energy plays a critical role in meeting the global energy challenge and represents one of the most promising energy sources for the future of the planet. Solar or photovoltaic cells are currently a hot topic on the market, these are devices that convert the energy of sunlight directly into electricity trough the photovoltaic effect. Strong and competitive research is currently devoted to lower the material costs of solar cells, and to increase their energy conversion efficiency. Up to now, commercially available photovoltaic technologies are based on inorganic materials, mainly crystalline silicon (first generation) and other semiconductors, such as gallium arsenide, indium phosphide and cadmium telluride (second generation In addition to high costs, also in terms of energy consuming, in fabrication processes, several of those materials are toxic and have low natural abundance. Therefore, in the last two decades the research focused on the development of a third generation of solar cells based on hybrid or organic materials, that offers a number of advantages, such as: high molar extinction coefficients, versatility of the chemical design for modulating the electronic properties, easy processability as well as low manufacturing costs. Although the efficiencies of organic-based photovoltaic cells ( 8%) are still at the moment a long way behind those obtained with purely inorganic based photovoltaic technologies ( 20%), the power conversion efficiency of organic solar cells have been significantly improved and there are expectations for more important results. Among the third generation of solar cells, the Dye-Sensitized Solar Cells (DSSC), also called Grätzel cells, have emerged as very promising candidates for low-cost alternative to conventional semiconductor photovoltaic devices. A DSSC cell scheme is shown in Figure 1. The cell components are: a mesoporous film of TiO2 (anode), a dye-sensitizer, an electrolyte, an electrochemical mediator and a cathode. The photovoltaic process in this cells can be resumed as follows: the dye-sensitizer (S), linked to semiconducting TiO2 surface (usually through a carboxylic group), absorbs a photon passing to the excited state S*, which transfers an electron to the conduction band of TiO2. The oxidized S+ thus obtained, is reduced by a redox mediator, generally I- from the couple I-/I3- dissolved in the electrolyte. The electron injected in TiO2 through the external circuit arrives to the cathode, where the reduction of I3- regenerates the iodide, closing the circuit. (Figure 1). Figure 1 The DSSC technology separates two requirements as: i) the charge generation, done at the semiconductor-dye interface and ii) the charge transport, done by the semiconductor and the electrolyte. Consequently, carrier transport properties can be improved by optimizing the semiconductor and electrolyte composition, while the spectral properties and thus charge generation can be improved by modifying the dye structure, that can be tailored in many ways by organic chemistry contribution. Many kinds of dyes have been studied for DSSCs application and in principle they could be divided in two classes (Figure 2): 1. metal complexes (N719, Zn-porphyrine e.g YD2-o-C8) , , 2. metal-free system Donor-Spacer-Acceptor (TA-St-CA) Figure 2 Up to now the best efficiencies (~11%) have been reached using ruthenium complexes, thanks to their large absorption range from visible to near infrared (NIR), and their capability to easily inject electrons in the conducting band of the semiconductor. The metal based chromophores still have several disadvantages such as not very high molar extinction coefficient and the presence of the expensive metal, such as ruthenium, which involves complicated synthesis and hard purification steps. On the contrary, metal-free dyes are simple and cheap to prepare and it is possible to easily modulate their photo- and electrochemical properties varying the functionalization, but very high efficiencies have not been achieved yet. The obtainment of new and more efficient dyes is therefore object of competitive international researches. Within this context, the present Ph.D. research project has focused on the synthesis of new metal-complexes and metal-free organic dyes characterized by a Donor-Spacer-Acceptor (D-π-A) structure, (Figure 3) in which the novelty is represented by the presence of benzo-condensed thiophene units as π bridge spacer. Figure 3 Aim of the work In such chromophores the π spacer plays a fundamental role, as it is responsible for the electronic communication between acceptor and donor moiety and for the extension of the conjugation that lead to wider and red-shifted absorption spectra. To date a number of new π-conjugated aromatic and heteroaromatic systems have been investigated and among these, thiophene or thienothiophene π-bridges have been reported to give remarkable efficiency. Benzodithiophenes systems BDT and BDT1 (Figure 4) attracted our attention because their rigid, π-conjugated, condensed-polycyclic structure , leads to unique electronic properties such as conductivity, high field effect mobility and tunable stacking in the solid state; rigid structures hamper the roto- vibrational modes responsible for the deactivation of the excited states in functional materials. Figure 4 In this Ph. D. work we investigated synthesis of suitably functionalized BDT and BDT1 derivatives as well as their use for the construction of two classes of dyes: 1) Zn-porphyrin based dyes (in collaboration with the research group of Prof. Pizzotti and Prof. Ugo) and 2) metal-free dyes and, Zn-porphyrin based dyes In addition the design of the new dyes have been oriented by preliminary theoretical calculations, done in collaboration with Dr. Filippo De Angelis of CNR-ISTM in Perugia, that allowed to gain insight into the molecular, ground and excited state electronic structure of the new chromophores. 1. Synthesis of new benzodithiophene containing Zn-porphyrins Metal porphyrins, characterised by very strong absorption bands around 450 nm (Soret band) and 600-700 nm (Q band) are potentially interesting as dyes for DSSC. For example, some push-pull type porphyrins bearing a carboxylic acid moiety as an anchoring group, have disclosed a remarkably high power conversion efficiency (6-7%), therefore in the recent years some research efforts have been devoted to the design, synthesis and application of new porphyrin-based chromophores for DSSC. , , The unique feature of these sensitizers is that the porphyrin chromophore itself constitutes the π-bridge of the D-π-A structure and with the aim of increasing the conjugation of the system, some new Zn porphyrins, containing the BDT1 unit (Figure 5), have been designed in our group. These porphyrin molecules are differently functionalized in 5,15 and 10,20 meso positions. In positions 5 and 15, aromatic rings bearing bulky groups are needed to avoid aggregation on the semiconductor surface, that drastically Figure 5 reduce the dye light-harvesting by a filtering effect. In 10,20 meso positions the structure presents two π-delocalized aromatic systems with opposite (electron-withdrawing or electron-donating) properties, in order to realize a push-pull system in which is possible to modulate the position and the intensity of the Q band and to favor the electron flow. The most promising structures were selected on the basis of preliminary theoretical calculations done by Dr. De Angelis and synthesized in collaboration with Prof. Ugo and Prof. Pizzotti’s research group. The novel Zn-porphyrin system 1 (Figure 6) was first synthesized, whose structure is characterized by the presence of BDT1 system in the acceptor part of the molecule. The suitable 2,6 di-functionalized BDT1 derivative was prepared and then linked to the porphyrin core. Figure 6 The resulting new Zn-porphyrin 1 was completely characterized from the analytical and photophysical point of view and used in preliminary tests as dye in Grätzel solar cells, giving an efficiency of 0.6%. Slightly optimization of the cell structure and in the composition of the electrolyte led to an increased efficiency of 2,54%. This result, although unsatisfactory, served as a starting point for the set-up of a number of synthetic protocols and for designing more targeted substitution and variation in the molecule structure. This part of the work is currently under progress. 2. Synthesis of benzodithiophene containing metal-free dye As already mentioned, the general structure of a metal-free dye, reported in Figure 3, presents a donor and an acceptor unit linked by a π-conjugate system. The most efficient structures reported in the literature contain triarylamines as donor unit, because of the prominent electron-donating ability and hole-transport of such molecules. Within this topic we designed novel metal-free triarylamine-containing organic dyes endowed with the innovative spacers BDT1 and its isomer BDT. Also in this case the design of the new compounds was oriented by preliminary TD-DFT calculations made by Dr. De Angelis, on two parent BDT1-containing structures 15 and 16, which differ from each other by the presence of a triple or a double bond. (Figure 7) With the aim to investigate the structure-performance relationship of the dyes in the cell, we designed a small library of structures, changing the BDT-bridge (17), the acceptor group (18) or the donor (19, 20) with respect of the model compound 16. (Figure 7). This allowed us to investigate the potentiality of BDT and BDT1 in the dyes in combination with double or triple bond in order to elongate the conjugation, and to obtain band gap reduction and enlarge the absorption spectra. In particular, the presence of the triple bond should ensures more planarity and therefore conjugation and avoids energy losses due to photoisomerization. The series of synthesized dyes are reported in figure 7. Figure 7 Almost all the dyes synthesized have also been characterized from a photophysical as well as electrochemical point of view, with the aim of identifying, among them, the most interesting and promising compounds for application in solar cells and try to clarify the relationship between the chemical structure and photovoltaic performances. Preliminary test in DSCs have been carried out for some of the dyes and among these dye 16 has emerged as the most promising one leading to an efficiency in liquid state cell of 5.11% and confirming the potential of BDT1 π-spacer for application in DSSCs. The cell efficiency found for 16, which is however still under optimization, allows us to say that this dye ranks among the promising dyes to date reported in literature. In addition, it must be pointed out that dye 16 seems to possess most of the essential chromophore characteristics required for obtaining high-performance DSSCs. The systematic study developed during the present Ph.D. thesis will be very useful for future improvement of the synthesized structures and their photovoltaic performances in DSSCs.

Dye-sensitized solar cell (DSSC) has attracted increasing interest as a promising hybrid organic-inorganic solar cell. At the heart of the device is a photosensitizer, which is anchored onto a wide-bandgap semiconducting metal oxide. It harvests solar light and transfers the energy via electron transfer to a suitable material (e.g. TiO2) to produce electricityas opposed to chemical energy in plant. The topic of this thesis focuses on the design and synthesis of metal-free organic dyes for applications in DSSCs. Specific attention has been paid to the correlation between the molecular structures and physical properties, as well as their performances in DSSCs. Chapter 1 presents the major components and working principle of DSSC, following by a brief overview of the development of organic dyes and their application in DSSCs. In chapter 2, we have designed two types of new phenothiazine-based dyes to investigate the positioning effect a donor group on the cell performance. The structural features of a donor aryl group at the C(7) position of phenothiazine core extend the π-conjugation of the chromophore and efficiently suppress the dye aggregation on TiO2 film. As a result, Type 1 dyes have better light harvesting properties in contact with TiO2 films, and give much better photovoltaic performance than Type 2 dyes. Chapter 3 presents the synthesis and characterization of a series of simple phenothiazine-based dyes, in which, a linear electron-rich (4-hexyloxy)phenyl group at C(7) of the phenothiazine periphery as the donor, and an alkyl chain with different length at N(10). The dye molecules show a linear shape which is favorable for the formation of a compact dye layer on the TiO2 surface, while their butterfly conformations can sufficiently inhibit molecular aggregation. Moreover, the alkyl substituents with different chain length at N(10) could further optimize the performance through complete shielding the surface of TiO2 from the Iˉ/I3ˉ electrolyte. Under simulated AM 1.5G irradiation, the PT-C6 based DSSC produces a short-circuit photocurrent of 15.32 mAcm−2, an open-circuit photovoltage of 0.78 V, a fill factor of 0.69, corresponding to a power conversion efficiency (PCE) of 8.18%. Moreover, we designed a stepwise approach for co-adsorption of the organic dye PT-C6 with a porphyrin dye (ZnP) for DSSCs. Upon optimization, the device made of the PT-C6 + ZnP system yielded Jsc = 19.36 mA cm-2, Voc =0.735 V, FF = 0.71 and η = 10.10%. In chapter 4, we further developed five organic dyes appended with T, TT, E, ET, or EE (T and E denote thiophene and 3,4-ethylenedioxythiophene (EDOT), respectively) on the C(7) atom of phenothiazine core as electron donors. We have also analyzed the structure-performance corelations of dye molecules in the aspect of dye aggregation, electron injection, dye regeneration and interfacial charge recombination of electrons with electrolytes and/or oxidized dye molecules, through DFT calculation, impedance analysis and transient photovoltage studies. In chapter 5, we extended our studies by using phenothiazine as a building block to construct 3D bulky organic dyes. We systematically investigated the influence of 3D bulky substituents on dye aggregation and charge recombination, as well as photovoltaic performance of DSSCs. The molecular design strategy demonstrates that high Voc can be realized by employing 3D-phenothiazine dyes featuring a bulky substituent, such as, hexylcarbazole and dihexylfluorene units. Impressively, the co-adsorbent-free DSSCs based on dye TP3 exhibits a photovoltaic performance with efficiency up to 8.00 %. In order to realize a panchromatic absorption and further enhance the energy conversion efficiency of DSSCs, we also designed a stepwise approach for co-adsorption of the organic dye TP3 with a NIR dye YR6 for co-sensitized DSSCs. Upon optimization, the device made of the TP3 + YR6 system yielded Jsc = 19.18 mA cm-2, Voc =0.721 V, FF = 0.712 and η = 9.84 %. The power-conversion efficiency is the highest reported efficiency for a squaraine dye-based co-sensitized panchromatic DSSCs. From chapters 6 and 7, a series of new simple panchromatic dyes based on thiadiazolo[3,4-c]pyridine (PyT) have been designed for panchromatic DSSCs. These new organic dyes exhibit broad absorption spectrum in the range of 300~850 nm and high molar extinction coefficients. The electrochemical analyses demonstrate that the incorporation of the auxiliary electron-deficient thiadiazole[3,4-c]pyridine unit can fine-tune the HOMO and LUMO energy levels and red-shift the absorption spectra to NIR region. The overall conversion efficiencies of liquid-electrolyte DSSCs based on these sensitizers range from 0.46 to 6.30 %. We draw some conclusions in chapter 8 together with the outlooks in DSSCs

Com foco nos últimos seis anos, o sistema bicíclico dicetopirrolopirrol tem sido cada vez mais utilizado como ”bloco de construção” de materiais (polímeros e moléculas pequenas) para utilização em células solares. Isso deve-se principalmente à sua alta estabilidade ambiental (principalmente fotoestabilidade) e capacidades de transferência de carga. Apesar dos estudos serem ainda recentes, os resultados já alcançados mostraram o tremendo potencial dos dicetopirrolopirróis em células solares. O trabalho descrito nesta tese de Mestrado envolveu a síntese de vários derivados de dicetopirrolopirrol com o objetivo de introduzir unidades fotossensibilizantes ligadas covalentemente ao sistema dicetopirrolopirrol. Os novos compostos podem vir a incorporar um grupo carboxílico para suportar o corante na superfície de um óxido semicondutor das células solares sensibilizadas por corantes (DSSCs). A primeira parte do trabalho consistiu na alquilação ou arilação dos grupos NH de dicetopirrolopirróis comerciais. Posteriormente, foram estudados métodos de funcionalização dos grupos arilo nas posições 3 e 6 dos DPP por reações catalisadas por paládio ou por clorossulfonação. Todos os dicetopirrolopirróis sintetizados foram caracterizados por ressonância magnética nuclear, espetrometria de massa e espectrofotometria de UV-visível. Alguns compostos foram também caracterizados por fluorescência; Abstract: With a focus on the last six years, the bicyclic diketopyrrolopyrrole (DPP) system has been increasingly used as an active building block in materials (polymers and small molecules) used in solar cells. That is mainly due to its high environmental stability (mainly photostability) and charge transfer capabilities. Despite its infancy, the results already achieved have shown the tremendous potential of diketopyrrolopyrroles in solar cells. The work reported in this Master thesis involved the synthesis of several diketopyrrolopyrrole derivatives aiming introducing photosensitizing units covalently linked to the diketopyrrolopyrrole system. The new compounds may be functionalized with carboxylic groups to support the dye firmly at the surface of a semiconductor oxide of dye-sensitized solar cells (DSSCs). The first part of the work consisted in the alkylation or arylation of the NH groups of commercially available DPP. Then, new methods for the functionalization of the aryl groups at 3 and 6 positions of DPP were studied, mainly by palladium catalysed reactions or by chlorosulfonation. All diketopyrrolopyrrole derivatives synthesized were characterized by nuclear magnetic resonance, mass spectrometry and UV-vis spectrophotometry. Some compounds were also characterized by fluorescence.

During the thesis the DSSCs optimization was analyzed mainly through two strategies: the study of new sensitizers and the study of alternatives materials for photo-cathode fabrication. Two class of sensitizers were be analyzed: squaraine dyes and cyclometalated-based dyes. Then a study on dye-loading process will be presented, with implication in an industrialization process. For the photo-cathode fabrication two di erent materials were studied, a carbon based material and a polymeric material. Then a part of the work concerned the study of devices analysis system. In particular electrochemical impedance spectroscopy was studied to propose a new set up to analyze electric processes in different cell components.3

Due to the strong increase in the world energy consumption, and need of exploiting carbon neutral energy sources, increasing efforts have been devoted to the exploitation of solar energy technology. For their unique properties, Dye Sensitized Solar Cells (DSSC) could complement the established silicon junctions. This Ph.D. thesis is mainly focused on the understanding of the (photo)/electrochemical properties of new components for DSSCs. The first chapter, realized in collaboration with the Prof. Stagni’s group, is about the characterization of new examples of Ru(II)-tetrazolato dyes as thiocyanate-free sensitizers for solar cell applications. Four complexes (D1-D4) have been analyzed together with the well know standard N719. The combination of the electrochemical and spectroscopic analyses revealed ground and excited states thermodynamic properties suitable for efficient interfacial charge separation. These features resulted in external quantum yield of photon to electron conversions higher than 80%. The best performances have been recorded in the case of D4 thanks to the combinations of the broader harvesting, efficient regeneration, and electron injection. Three chapters of my thesis report about the collaborative research carried out with the groups led by Dr. P.C. Gros and Dr. M.C. Pastore, involving the investigation of the electronic properties of Fe(II)NHC (NHC=N-Heterocyclic-Carbene) sensitizers. First, we tried to rationalize the charge transfer dynamics of C1 a homoleptic complex bearing σ-donating NHCs and π-accepting carboxylic groups, which initially reported rather low performances (0.13 % of PCE%). We achieved a substantial progress in cell efficiency (PCE = 1%). We estimated an injection quantum yield (Φinj) of ca. 50% that, is believed to be the main limitation for the rather low PCE. In consideration of the excited state energetics, nearly optimal for injection into TiO2, this relatively low Φinj could be due to a non-optimal electronic coupling arising from the symmetric design of the homoleptic C1. For this reason, we moved to Fe(II)NHC heteroleptic designs characterized by an asymmetric coordination sphere. The first complex was the asymmetric analogue of C1 named ARM13, while other design incorporated spacers between the anchoring moieties and the pyridine linked to the metal center, in particular, a thiophene in the case of ARM7 and a phenyl ring in the case of ARM11. The rationale behind such designs was to increase the electron-hole separation and the light harvesting capability. We were able to obtain the highest power conversion efficiency (ARM13 ca. 1.5%) ever reported for a Fe(II) sensitizer. In a third project, we designed, realized and characterized a new family of heteroleptic Fe(II)NHC complexes bearing electron withdrawing or donating substituents on the ancillary ligands. In particular, among the new series, ARM130 bearing a dimethoxyphenyl group, exhibited the best performance, thanks to its improved light harvesting capability introduced by the electron-donating -OMe moieties. We obtained a Power Conversion Efficiency of 1.83%. The last chapter of my thesis is about the investigations of alternative counter electrode (CE) materials for DSSCs based on the poly(3,4-ethylenedioxythiophene) (PEDOT) conductive polymer. The best and well-known electrocatalyst PEDOT/ClO4 (PER) involves the use of organic solvents, greener and sustainable alternative deposition routes are desirable. We explored the electrochemical properties of PEDOT/Nafion CE (NAF), produced through water- based electropolymerization. The electrocatalytic behavior of PER and NAF has been investigated in STLC by means of LSV and EIS, in the presence of either Co- or Cu- based electrolyte, NAF rivals the kinetic and mass transport properties of PER. This result was confirmed by the performance of D35 sensitized solar cells, where NAF counter electrodes generated comparable efficiency of those recorded for PER.<br>A causa dell’aumento della richiesta energetica e della necessità di esplorare risorse sostenibili, ingenti sforzi sono rivolti verso l’applicazione di tecnologia solare. Grazie alle loro peculiarità, le Celle Solari Sensibilizzate con Colorante (DSSCs) potrebbero essere uno strumento complementare alla tecnologia al silicio. Questa tesi di Dottorato è incentrata nella comprensione delle proprietà (foto)/elettrochimiche di nuovi componenti per DSSCs. Il primo capitolo sperimentale, realizzato in collaborazione con il gruppo del Prof. Stagni, ha avuto come scopo la caratterizzazione di nuovi sensibilizzatori di Ru(II)-tetrazolati come esempio di complessi privi di leganti tiocianati. Quattro complessi (D1-D4) sono stati studiati assieme al ben noto standard di rutenio N719. La combinazione dell’analisi elettrochimica e spettroscopica ha evidenziato come la termodinamica dello stato fondamentale ed eccitato sia in grado di favorire un’efficiente separazione di carica. Queste caratteristiche hanno portato ad una resa quantica di conversione di fotoni in elettroni superiore all’80%. D4 è risultato essere il complesso più efficiente grazie alla combinazione della più estesa estensione spettrale, efficiente rigenerazione ed efficiente iniezione di carica. Gran parte della mia attività, tuttavia, è stata rivolta allo studio di sensibilizzatori per DSSCs a base di ferro. Tre capitoli, in collaborazione con i gruppi del Dr. P. C. Gros e dalla Dr. M. C. Pastore, riportano l’investigazione delle proprietà elettroniche di sensibilizzatori di Fe(II)NHC. Nel primo di questi abbiamo studiato le proprietà di trasferimento dinamiche di un complesso omolettico denominato C1, caratterizzato da leganti NHC σ-donatori e gruppi carbossilici π-accettori, il quale aveva inizialmente restituito valori di efficienza dello 0.13%. Abbiamo ottenuto un sostanziale aumento di efficienza ottenendo valori vicini all’1%. Il rendimento quantico di iniezione di carica è risultato essere attorno al 50% e costituisce il principale fattore limitante per le DSSCs a base di ferro. L’energetica dello stato eccitato è risultata ottimale per un’efficiente iniezione di carica quindi, le limitate prestazioni esibite da C1 derivano dal suo design simmetrico che porta ad un accoppiamento elettronico non favorevole con la superficie. Abbiamo così analizzato complessi carbenici eterolettici, il primo di questi era l’analogo asimmetrico di C1, ARM13, altri due invece erano caratterizzati dall’introduzione di un anello tiofenico (ARM7) e uno fenilico (ARM11) aventi la funzione di spaziatori fra le funzionalità ancoranti e le piridine coordinate al metallo centrale. L’idea di questo nuovo design era quella di aumentare la separazione di carica ed incrementare la capacità di raccolta di fotoni. Abbiamo ottenuto la più alta efficienza di cella riportata in letteratura del 1.5% per ARM13. In un terzo progetto abbiamo analizzato una nuova famiglia di complessi eterolettici caratterizzati dall’introduzione di gruppi elettron-donatori o elettron-attrattori sui leganti ancillari. ARM130, caratterizzato da una funzionalità dimetossifenilica, ha restituito le migliori performances dell’1.83%. L’ultimo capitolo della mia tesi riguarda invece lo studio di un controelettrodo (CE) alternativo per DSSCs basato su polimeri conduttori a base di poli(3,4-etilendiossitiofene) (PEDOT), fra questi il ben noto PEDOT/ClO4 (PER), elettropolimerizzato da solventi organici, risulta essere il miglior materiale elettrocatalitico. Al fine di studiare soluzioni più sostenibile, abbiamo esplorato le proprietà elettrochimiche di CE a base di PEDOT/Nafion (NAF) prodotti in ambiente acquoso. Il comportamento elettrocatalitico di PER e NAF è stato investigato in celle simmetriche mediante LSV ed EIS e in celle solari in presenza di D35, quest’ultimo ha generato efficienze di cella comparabili a quelle registrate in presenza di PER.

En raison des problèmes d'instabilité à moyen termes des cellules solaires à colorant (DSSC), l'électrolyte liquide à base d'iodure a été remplacé par plusieurs types de matériaux solides transport de trous (HTM) pour obtenir des DSSCs à l'état solide (s-DSSCs). Parmi ces matériaux, l’utilisation des polymères conducteurs(PC) a attiré une attention considérable en raison de leur bonne stabilité, de leur haute conductivité et de la facilité de leur dépôt sur le semi-conducteur mésoporeux TiO2. Dans ce travail de thèse, plusieurs s-DSSCs basées sur des PC utilisés comme HTM ont été développés dans le but d'améliorer leurs performances photovoltaïques en tenant compte des deux objectifs suivants: (i) l'optimisation des processus de transfert inter facial de charge dans la cellule solaire, et (ii) l'optimisation du transport de charge dans le semi-conducteur d'oxyde de type n. Pour atteindre ces objectifs, chaque composant de la s-DSSC a été modifié afin d'étudier son effet sur les performances du dispositif final. En première tentative, une étude analytique est réalisée en faisant varier le sensibilisateur afin de déterminer les fragments de la structure du colorant, qui ont un effet important sur le processus de photopolymérization électrochimique in-situ (PEP) à la fois en milieu organique et en milieu aqueux mais aussi sur les performances des s-DSSCs. Sur la base de ces résultats, un nouveau concept a été développé et consiste en la suppression totale de l'interface entre le colorant et le HTM. Ceci est obtenu par la synthèse de nouveaux colorants liés de façon covalente à un monomère électroactif qui est co-polymérisé par la PEP in-situ. Le copolymère résultant, utilisé comme HTM, est lié de manière covalente au colorant. En outre, la nature de la liaison chimique, reliant le résidu triphénylamine TPA au monomère, est également étudiée comme un facteur clé dans les performances de s-DSSC. En outre, et pour optimiser les processus de transport de charges dans ce type de s-DSSC, de nouvelles s-DSSC basées sur ZnO ont été réalisées et étudiées<br>Due to instability problems of dye sensitized solar cells (DSSCs) in longtime uses, the iodine based liquidelectrolyte has been replaced by several types of solid hole transporting materials (HTM) to perform solidstate DSSCs (s-DSSCs). Among them, the substitution by conducting polymers (CP) has attractedconsiderable attention because of their good stability, high hole-conductivity and simple deposition withinthe mesoporous TiO2 semiconductor. In this thesis work, several s-DSSCs based on CPs used as HTM havebeen developed in order to improve their photovoltaic performances taking into account the following twoobjectives: (i) the optimization of the interfacial charge transfer processes within the solar cell, and (ii) theoptimization of the charge transport within the n-type oxide semiconductor. To reach these goals, eachcomponent that constitutes the device was varied in order to investigate its effect on the device’sperformances. As first attempt, an analytical study is carried out by varying the sensitizer in order todetermine the fragments of the dyes structures, that have an important effect on the in-situ photoelectrochemical polymerization process (PEP) both in organic and in aqueous media and hence on theperformances of the s-DSSCs. Based on these results, a new concept of removing completely the interfacebetween the dye and the HTM is developed. This is achieved by the synthesis of new dyes covalently linkedto an electroactive monomer which is co-polymerized by in-situ PEP. The resulting co-polymer, used asHTM, is covalently linked to the dye. In addition, the nature of the chemical bond linking the triphenylamineresidue TPA to the monomer is also investigated as a key factor in the s-DSSCs performances. Besides, andto optimize the charge transport processes within this type of s-DSSC, the elaboration of novel ZnO baseds-DSSCs has been achieved and investigated