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1.
ACS Appl Mater Interfaces ; 8(39): 26002-26007, 2016 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-27599592

RESUMO

Organometal halide perovskites have been recognized as a new class of materials for photovoltaic application. Solvent annealing introduced during crystallization of bulk or thin-film materials can improve the performance of perovskite solar cells. Herein, we present Kelvin probe force microscopy and conductive atomic force microscopy (c-AFM) measurements to investigate the local optoelectronic properties of a perovskite film after N,N-dimethylformamide (DMF) annealing. AFM results show that DMF annealing induces recrystallization, yielding a large-size polycrystalline perovskite film. Uniform and higher photocurrent is distributed on the film. However, lower surface potential enhancement and photocurrent are observed at grain boundaries (GBs), illustrating that GBs acting as recombination sites are detrimental to photocurrent transport and collection. Our observation provides a nanoscale understanding of the device performance improvement after DMF annealing.

2.
ACS Appl Mater Interfaces ; 7(51): 28518-23, 2015 Dec 30.
Artigo em Inglês | MEDLINE | ID: mdl-26633192

RESUMO

Grain boundaries (GBs) play an important role in organic-inorganic halide perovskite solar cells, which have generally been recognized as a new class of materials for photovoltaic applications. To definitely understand the electrical structure and behavior of GBs, here we present Kelvin probe force microscopy and conductive atomic force microscopy (c-AFM) measurements of both typical and inverted planar organolead halide perovskite solar cells. By comparing the contact potential difference (CPD) of these two devices in the dark and under illumination, we found that a downward band bending exists in GBs that predominantly attract photoinduced electrons. The c-AFM measurements observed that higher photocurrents flow through GBs when a low bias overcomes the barrier created by the band bending, indicating that GBs act as effective charge dissociation interfaces and photocurrent transduction pathways rather than recombination sites.

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