Reaction of Metallic Lead (Pb) and Polyiodide (MAI3) Opens New Route to Fabricate MAPbI3 Perovskite Solar Cells
Said Kazaoui a, Ivan Turkevych b, Sonya Kosar c, Eugene Goodilin d, Alexey Tarasov d, Michael Graetzel e
a Research Center for Photovoltaics (RCPV), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
b Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Tokyo, Japan
c Okinawa Institute of Science and Technology (OIST), Okinawa, Japan
d Lomonosov Moscow State University, Lenin Hills, Moscow, Russian Federation
e Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of International Conference on Perovskite and Organic Photovoltaics and Optoelectronics (IPEROP19)
Kyōto-shi, Japan, 2019 January 27th - 29th
Organizers: Hideo Ohkita, Atsushi Wakamiya and Mohammad Nazeeruddin
Poster, Said Kazaoui, 099
Publication date: 23rd October 2018

Perovskite solar cells (PVs) are attracting the attention of academia and industry due to their high efficiency and relatively low-cost fabrication. However higher efficiency and stability, as well as further cost reduction are highly demanded to meet the requirements for future commercialization.

Here, we report a novel method to fabricate perovskite absorber layers and solar cells based on the reaction between metallic lead (Pb) film and polyiodide (MAI3) melt, which is form according to the following unique reactions: MAI(s)+I2(v)→MAI3(L) then MAI3(L)+Pb(0)(s)→MAPbI3(s) [1, 2]. The iodization reaction MAI(s)+I2(v)→MAI3(L), which is controlled by I2 partial vapor pressure, forms a very reactive MAI3(L) polyiodide melt (liquid) that converts Pb(0)(s) solid into MAPbI3(s) solid without using organic solvents at ~50oC and ~1atm. We stress that the crucial steps are the iodization reaction MAI(s)+I2(v)→MAI3(L) and oxidation reaction Pb(0)→Pb(2+) that control of the oxidation state (e.g. Pb(2+)) and defect density (e.g. I-,MA+) of the perovskite.

Experimentally, a thin layer of metallic Pb (typically ~60nm deposited by vacuum technique on various substrates) was coated with stoichiometric amounts of MAI or CsI/MAI/FAI (typically ~200nm deposited by vacuum technique) and subsequently was exposed to iodine vapor (typically at ~50oC and ~1atm). The instantly formed MAI3(L) or Cs(MA,FA)I3(L) polyiodide liquid readily converts the Pb layer into MAPbI3(s) or (Cs0.05MA0.15FA0.75)PbI3(s) perovskite film without byproducts. It worth mentioning that our method is in a striking contrast to PbI2+MAI→MAPbI3 using either organic solvent or vacuum techniques. Interestingly our novel method shares some similarities with the techniques used to synthesis Copper-Indium-Gallium-Selenide (CIGS) solar cells. As a proof-of-concept, we demonstrate small area solar cells with power conversion efficiencies of 16.12% (planar MAPbI3), 17.18% (mesoscopic MAPbI3) and 16.89% (planar Cs0.05MA0.15FA0.75PbI3) in the standard FTO/TiO2/Perovskite/Spiro-OMeTAD/Au architecture.

Detailed investigations of the perovskite absorber layers and solar cells will be reported at this conference.

We thank Nikolai A. Belich, Aleksei Y. Grishko, Sergey A. Fateev and Andrey A. Petrov (from Lomonosov Moscow State University (MSU)) for their great contribution to this work. These authors contributed equally: Ivan Turkevych, Said Kazaoui. Reference [2] is also available from SharedIt link: https://rdcu.be/bb0aA

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