Graded morphologies and the performance of pffbt4t-2od:Pc71 bm devices using additive choice

• Autor(a) principal: Hugo Gaspar
• Data de Publicação: 2021
• Outros Autores: Andrew Parnell, Gabriel Pérez, Júlio Viana, Stephen King, Adélio Mendes, Luiz Pereira, Gabriel Bernardo
• Tipo de documento: Artigo
• Idioma: por
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: https://hdl.handle.net/10216/140877
• topic: Química, Engenharia química; Chemistry, Chemical engineering

The impact of several solvent processing additives (1-chloronaphthalene, methylnaph-thalene, hexadecane, 1-phenyloctane, and p-anisaldehyde), 3% v/v in o-dichlorobenzene, on the performance and morphology of poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3′ ′ ′-di(2-octyldodecyl)-2,2′,5′,22033,5′ ′,2′ ′ ′-quaterthiophen-5,5′ ′ ′-diyl)] (PffBT4T-2OD):[6,6]-phenyl-C71-butyric acid methyl ester (PC71 BM)-based polymer solar cells was investigated. Some additives were shown to enhance the power conversion efficiency (PCE) by ~6%, while others decreased the PCE by ~17-25% and a subset of the additives tested completely eliminated any power conversion efficiency and the operation as a photovoltaic device. Grazing-Incidence Wide Angle X-ray Scattering (GIWAXS) revealed a clear stepwise variation in the crystallinity of the systems when changing the additive between the two extreme situations of maximum PCE (1-chloronaphthalene) and null PCE (hexadecane). Small-Angle Neutron Scattering (SANS) revealed that the morphology of devices with PCE ~0% was composed of large domains with correlation lengths of ~30 nm, i.e., much larger than the typical exciton diffusion length (~12 nm) in organic semiconductors. The graded variations in crystallinity and in nano-domain size observed between the two extreme situations (1-chloronaphthalene and hexadecane) were responsible for the observed graded variations in device performance.