Processus de transfert de charges et de transport dans les cellules photovoltaïques organiques à base de composites MEH-PPV : C60

Le travail présenté dans ce mémoire porte sur la réalisation et l'étude de cellules photovoltaïques organiques dont le constituant de base est un composite donneur:accepteur MEH-PPV :C60. Nous avons principalement étudié des structures de diodes photovoltaïques organiques de type ITO/MEH-PPV :C60/Al. Le film organique était composé du polymère MEH-PPV, matériau donneur d'électrons, et de molécules de fullerènes C60, se comportant en accepteur d'électrons. Cette étude a montré l'étroite interdépendance entre la morphologie des composites et les propriétés photovoltaïques des cellules réalisées. Nous avons étudié l'influence de la concentration des fullerènes sur le processus de dissociation des paires photogénerées et de transport des charge. Nous avons également étudié les variations des paramètres photoélectriques en fonction du solvant organique (THF ou ODCB) employé pour déposer la couche photoactive. Ces effets ont pu être corrélés aux différentes morphologies résultant des conditions d'élaboration. Les meilleures performances photoélectriques ont été obtenues avec un nouveau protocole de mélange. Nous avons introduit des molécules de colorants organiques dans la couche active du composite MEH-PPV:C60 dans le but d'augmenter l'absorption des photons du spectre solaire par la couche photoactive. L'incorporation de PcH2 et de Coumarine 343, a considérablement augmenté les performances photovoltaïques des cellules ainsi élaboréesLYON1-BU.Sciences (692662101) / SudocSudocFranceF

Influence of the processing conditions on charge transfer and transport properties in poly(2-methoxy-5-(2 '-ethylhexyloxy)1-4-phenylenevinylene): C-60 composites for photovoltaics

International audiencePolymer-based photovoltaic devices have been elaborated by blending the conjugated polymer, poly(2-methoxy-5-(2'-ethylhexyloxy)1-4-phenylenevinylene) (MEH-PPV) with the buckminsterfullerene, C60. The solvent used has a main influence on the optical and electrical properties of the photoactive layers. This could be attributed to different dispersion abilities of C60 in the polymer layers shown by Atomic Force Microscopy and Scanning Electron Microscopy. Its effect on the transfer and transport properties has been studied. Thin film processing conditions have been modified by the preparation of blends of solutions of the polymer in Tetrahydrofuran and fullerene in Ortho-dichlorobenzene. The resulting spin casted layers show improved morphologies implying better dispersion of the fullerenes and increased short circuit currents. A decrease in the fullerene critical concentration to form percolation paths has been demonstrated. The improvement of the photovoltaic properties of the MEH-PPV/C60 composites has been attributed to the nanosized fullerene domains formed upon phase separation. We used optical spectroscopy to study the charge transfer efficiency and electrical measurements to investigate charge transport properties in MEH-PPV:C60

Photoluminescence response of MEH-PPV: MWCNTs and MEH-PPV: PS-MWCNTs nanocomposites: Optimization of charge transfer process

International audienc

Conducting polymer functionalized multi-walled carbon nanotubes nanocomposites: Optical properties and morphological characteristics

International audienceDonor/acceptor heterostructures formed by a donor conducting polymer and carbon nanotubes as acceptor materials are elaborated. Carbon nanotubes (CNTs) have been functionalized with polystyrene. A huge potential for functionalized CNTs for an effective charge transfer was shown. Moreover, optical properties have been correlated with morphological characteristics. We conclude that there is a relationship between the morphology and the performances of polymer/CNTs bulk heterojunction nanocomposites, integrated as photoactive layer for photovoltaic application

Nanomaterials for photovoltaic conversion

International audienceA promising route for photovoltaic conversion has emerged from the combination of electroactive nanomaterials and small bandgap polymers. The formation of bulk heterojunctions resulting from the extended interfaces leads to efficient dissociation of the charge pairs generated under sunlight shown by the rapid extinction of the polymer photoluminescence for increasing contents of fullerenes or TiO2 nanoparticles in MEH-PPV or PVK. Unconventional elaboration routes of the blends have been developed to increase the nanofiller dispersion and inhibit phase separation at high concentration. The size reduction of the acceptor domains led to a complete quenching of the radiative recombinations, obtained by specific solvent processing of MEH-PPV / C60 nanocomposites or sol gel elaboration of TiO2 nanoparticles in a PVK film. A simultaneous increase of the photocurrents could be achieved by the dispersion and size optimisation of the nanofillers. In situ generation of silver particles in MEH-PPV provides an example of enhanced charge separation induced by the plasmon resonance at the metal/polymer interface. The strong influence of the molecular morphology on the nanocomposite properties emphasizes the large improvements which can still be gained on the performances of organic solar cells

Photoluminescence response of MEH-PPV: MWCNTs and MEH-PPV: PS-MWCNTs nanocomposites: Optimization of charge transfer process

International audienc