Direct Observation of Long Electron-Hole Diffusion Distance in CH3NH3PbI3 Perovskite Thin Film.

ABSTRACT: In high performance perovskite based solar cells, CH3NH3PbI3 is the key material. We carried out a study on charge diffusion in spin-coated CH3NH3PbI3 perovskite thin film by transient fluorescent spectroscopy. A thickness-dependent fluorescent lifetime was found. By coating the film with an electron or hole transfer layer, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) or 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD) respectively, we observed the charge transfer directly through the fluorescence quenching. One-dimensional diffusion model was applied to obtain long charge diffusion distances in thick films, which is ~1.7??m for electrons and up to ~6.3??m for holes. Short diffusion distance of few hundreds of nanometer [corrected] was also observed in thin films. This thickness dependent charge diffusion explained the formerly reported short charge diffusion distance (~100?nm) in films and resolved its confliction to thick working layer (300-500?nm) in real devices. This study presents direct support to the high performance perovskite solar cells and will benefit the devices' design.

SUBMITTER: Li Y 

PROVIDER: S-EPMC4586438 | biostudies-literature | 2015 Sep

REPOSITORIES: biostudies-literature