Synthesis and characterization of photovoltaic materials for low cost and high efficiency solar panels

Abstract

[Abstract] This dissertation studies the use of the hybrid perovskite (CH3)2NH2PbI3 in solid-state dye sensitized solar cells (ssDSSC), which was not previously described in the literature. To that end, thin films of the perovskite were prepared using both the one-step spin-coating and the two-step spin-coating techniques. Those films were characterized by XR powder diffraction and scanning electron microscopy. Furthermore, the UV-Vis spectrum of the compound was obtained, as well as its band gap and structure. The UV-visible absorption spectrum of the (CH3)2NH2PbI3 revealed that it absorbed only in the blue region and the ultraviolet zone, while its band gap was 2.81 eV. Although these optical properties are not adequate for photovoltaic applications, they it make an interesting candidate for use in a blue LED design. The structure of the compound is that of a hexago-nal perovskite, due to the big size of the dimethlyammonium cation. At first, a non-homogenous layer of (CH3)2NH2PbI3 was deposited, with a needle-like structure, and which was due to a large particle size of the precursor solutions. The particle size of the solutions was proved to be in relationship with the amount of organic com-pounds present in the solution, as it was reduced adding MAX or DMAX as additives (me-thyl or dimethlylammonium halides, where X is either Cl- or I-). Also, this memory reports the influence of the additives in the particle size of the colloids and in film morphology on hybrid perovskite CH3NH3PbI3. The obtained results shown that methylammonium chloride employed as additive induces a reduction of particle size of the precursor solutions leading to better, more homogeneous morphologies.

[Resumo] This dissertation studies the use of the hybrid perovskite (CH3)2NH2PbI3 in solid-state dye sensitized solar cells (ssDSSC), which was not previously described in the literature. To that end, thin films of the perovskite were prepared using both the one-step spin-coating and the two-step spin-coating techniques. Those films were characterized by XR powder diffraction and scanning electron microscopy. Furthermore, the UV-Vis spectrum of the compound was obtained, as well as its band gap and structure. The UV-visible absorption spectrum of the (CH3)2NH2PbI3 revealed that it absorbed only in the blue region and the ultraviolet zone, while its band gap was 2.81 eV. Although these optical properties are not adequate for photovoltaic applications, they it make an interesting candidate for use in a blue LED design. The structure of the compound is that of a hexago-nal perovskite, due to the big size of the dimethlyammonium cation. At first, a non-homogenous layer of (CH3)2NH2PbI3 was deposited, with a needle-like structure, and which was due to a large particle size of the precursor solutions. The particle size of the solutions was proved to be in relationship with the amount of organic com-pounds present in the solution, as it was reduced adding MAX or DMAX as additives (me-thyl or dimethlylammonium halides, where X is either Cl- or I-). Also, this memory reports the influence of the additives in the particle size of the colloids and in film morphology on hybrid perovskite CH3NH3PbI3. The obtained results shown that methylammonium chloride employed as additive induces a reduction of particle size of the precursor solutions leading to better, more homogeneous morphologies.

[resumen] Este traballo estuda o uso da perovskita híbrida (CH3)2NH2PbI3 en células solares sensitivi-zadas por colorantes de estado sólido (ssDSSC), a cal non fora descrito anteriormente na bibliografía. Para ese fin, capas finas da perovskita foron preparadas polos procedementos de spin-coating en un e dous pasos, respectivamente. Esas capas foron caracterizadas por difracción de raios-X en po e por microscopía electrónica de varrido. Ademais, o espectro de UV-Vis foi obtido, así como o seu bandgap e a súa estrutura. O espectro de absorción de UV-visible do (CH3)2NH2PbI3 revelou que este solo absorbía na rexión ultravioleta, mentres que o seu band gap era 2.81 eV. Aínda que estas propiedades non eran adecuadas para aplicacións fotovoltaicas, tamén o fan un candidato interesante para o seu uso nun LED azul. A estrutura cristalina do composta é a dunha perovskita he-xagonal, debido o gran tamaño do catión dimetilamonio. Ao principio depositouse unha capa non homoxénea de (CH3)2NH2PbI3, cunha estrutura en forma de agullas, o calé debido ao gran tamaño de partícula das disolucións precursoras. Demostrouse que o tamaño de partícula das solución precursoras esta relacionado coa can-tidade de compostos orgánicos presentes na disolución, xa que foi reducido ao engadir MAX ou DMAX como aditivos (haluros de metil o dimetil amonio, sendo X ben Cl- ou I-). Esta memoria tamén reporta a influencia dos aditivos nos coloides e na morfoloxía das ca-pas da perovskita híbrida CH3NH3PbI3. Os resultados obtidos mostran que o emprego de cloruro de metilamonio como aditivo induce unha redución do tamaño de partícula das solución precursoras, levando á obtención de morfoloxías mellores e máis homoxéneas.