Light Induced Ion Migration in Bi-Doped MAPbI3 for Enhanced Photo-Stability
Alicia de Andrés a, Carlos Redondo-Obispo b, Esteban Climent-Pascual a c, Javier Bartolomé-Vilchez a, Carlos Zaldo a, Carmen Coya b
a Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, Madrid 28049, Spain
b Escuela Técnica Superior de Ingeniería de Telecomunicación (ETSIT), Universidad Rey Juan Carlos
c Escuela Técnica Superior de Ingeniería Industrial, Universidad Politécnica de Madrid
nanoGe Perovskite Conferences
Proceedings of International Conference on Perovskite Thin Film Photovoltaics and Perovskite Photonics and Optoelectronics (NIPHO20)
Sevilla, Spain, 2020 February 23rd - 25th
Organizer: Hernán Míguez
Oral, Alicia de Andrés, presentation 051
Publication date: 25th November 2019

The extraordinary efficiency values reached with MAPbI3 (MA: CH3-NH3) based photovoltaic cells has recently boosted the efforts in the search of new hybrid perovskite alternatives for photovoltaic energy production. These perovskites have in common a high sensitivity to water and oxygen as well as to visible irradiation, there issues strongly handicap their stability. Obtaining more stable compounds as well as understanding the complex behavior of the band-to band emission upon illumination and time are main concerns to be tackled. The photoluminescence behavior is strongly sensitive to different parameters, especially to the presence of defects and traps whose evolution with time is related to ion migration and perovskite transformations [1], [2].

Our approach is to introduce BiI3 in the synthesis of MAPbI3 films to stabilize the compound. The impact of incorporating a non-isovalent cation in the structure and morphology of the films is studied. XRD analysis allows confirming the incorporation of Bi3+ into the perovskite lattice up to around 7 at% at the Pb2+ site. The grain aspect ratio is reduced and the films are densified. Bi3+ incorporation leads to a slight increment of the optical gap due to the reduction of lattice parameters. The presence of empty Bi gap states quenches the 770 nm red interband emission and results in a near-infrared emission at 1100 nm. However, high enough visible irradiation density induces a progressive segregation of Bi3+ out of the perovskite lattice and promotes the re-emergence of the red emission. This emission is blue shifted and its intensity increases strongly with time until it reaches a saturation value which remains stable in the transformed films for extremely high power densities, around 1000 times higher than for undoped samples. We propose that the underlying processes include the formation of BiI3 and BiOI, probably at the surface of the crystals, hampering the usual decomposition pathways into PbI2 and PbOx for undoped MAPbI3 [3]. These results provide a new path for obtaining highly stable materials which would allow an additional boost of hybrid perovskite-based optoelectronics.

 

Funding by the Spanish Ministerios under Projects MAT2015-65356-C3-1-R, MAT2015-65356-C3-2-R, RTI2018-096918-B-C41 and ENE2017-90565-REDT National Excellence Network is acknowledged. We also acknowledge MINECO for financial support and provision of synchrotron radiation facilities at the European Synchrotron Radiation Facility (ESRF) and thank Eduardo Salas for his assistance in using Spanish beamline BM25A SpLine at ESRF. J.B. acknowledges the funding from Comunidad de Madrid under the Talento fellowship 2017-T2/IND-5617.

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