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Irving Caballero
José_Luis Maldonado
Acceso Abierto
Organic solar cells
Scanning tunneling microscopy
Scanning tunneling spectroscopy
Atomic force microscopy
"In this Ph. D. dissertation Scanning Probe Microscopies (SPM) are used for the analysis of semiconducting polymers and small molecules layers widely used in organic solar cells (OSCs). Scanning Tunneling Microscopy (STM) images of PEDOT:PSS film shows an ellipsoidal shape of PEDOT surrounded by PSS with 4 nm size. STM images of P3HT reveal that films tend to form well-defined crystalline domains with an average interchain distance around 1.41 nm and a chain length ~41 nm. PTB7 chains are self-aggregated by using chlorobenzene as solvent; however, when using 1-phenyloctane with 3% of DIO, these chains show a worm-like pattern with a distance of ~2 nm between backbone chains and a chain length of ~90 nm. Besides, by using STM and Scanning Tunneling Spectroscopy (STS), morphology evolution process and energetic level alignment of very thin solid films (thickness: < 700 pm), of the low molecular weight molecule DRCN5T and DRCN5T [70]PCBM blend are analyzed after applying thermal annealing at different temperatures. These films exhibit a worm-like pattern without thermal annealing (amorphous shape); however, after applying thermal annealing at 120°C, the small molecule film domains crystallize: structural geometry becomes a well-defined organized array. Furthermore, energy band diagrams of the semiconductor bulk heterojunction (blended film) at the donor-acceptor interface are determined by STS. Here is also reported the possible application of carbo-benzenes derivatives as Self-Assembled Hole Transport Monolayer (SA-HTM) –analyzed by STM– to replace the most common p-type contact, PEDOT:PSS, in OSCs. In addition, SPM are used for the analysis of PBDB-T, ITIC and PBDB-T:ITIC layers. STM images of PBDB-T reveal that thin films (< 1 nm) tend to form worm-like pattern domains with an average chain-to-chain distance of 950 pm; likewise, STM images of ITIC show that side arms form chain-like patterns. Meanwhile, STM images of PBDB-T:ITIC blend suggest why PBDB-T domains could facilitate charge dissociation, further, a strong inter-chain π-π interaction of the ITIC molecules form the electron transport continuous pathways for efficient charge collection. Moreover, when correlating Electrostatic Force Microscopy (EFM) and photoconductive Atomic Force Microscopy (pc-AFM), the blend morphology and its electrical/electronic properties are determined; the ideal domain size of PBDB-T:ITIC blend phases for maximizing the generated photocurrent is 15-35 nm."
Tesis de doctorado
León, Guanajuato
Público en general
Caballero Quintana, (2020). "Analysis of organic solar cells films through scanning probe microscopies". Tesis de Doctorado en Ciencias (Óptica). Centro de Investigaciones en Óptica, A.C. León, Guanajuato. 93 pp.
Versión aceptada
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