Rapid CH3NH3PbI3 Formation by MethylAmine Gas-Induced Reaction and its Characterization by Impedance Spectroscopy
Luis K. Ono a, Sonia R. Raga a, Yabing Qi a
a OIST, 1919-1 Tancha, Onna-son, Okinawa, 904, Japan
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of International Conference Asia-Pacific Hybrid and Organic Photovoltaics (AP-HOPV17)
Yokohama-shi, Japan, 2017 February 2nd - 4th
Organizers: Tsutomu Miyasaka and Iván Mora-Seró
Poster, Sonia R. Raga, 041
Publication date: 7th November 2016

We developed a novel method to fabricate CH3NH3PbI3 perovskite by simply exposing lead iodide films to methylamine (MA) and hydroiodic acid (HI) gases. The process can be easily up-scaled, and can be carried out in a few minutes, at temperatures below 80°C, at 50% relative humidity. This method simplifies the process by avoiding the step of synthetizing the methylammonium iodide precursor. Solar cell efficiencies up to 15% were achieved and good stability was observed for devices stored for 130 days.1

In addition, the perovskite films resulting from the intermediate steps of this fabrication process contain a large number of impurities in the form of lead oxide/hydroxides or PbI2. Defects can form in the vicinity of such impurities, affecting the photovoltaic performance. We analyzed the impedance spectroscopy response of several devices fabricated with the films containing different amounts of impurities. The aim was to correlate the different resistances such as charge recombination with the amount of impurities in the film and also high quality perovskite and lead iodide only. We found minor variations in photovoltage (Voc), independently of the content of impurities. It was also found that the recombination feature does not correlate with the low frequency arc of the Nyquist, instead, it is more likely correlated with the high-frequency arc, when the scan is measured at voltages near Voc.2

1 Sonia R. Raga, Luis K. Ono, Yabing Qi*, J. Mater. Chem. A, 2016, 4, 2494

2 Sonia R. Raga, Yabing Qi*, J. Phys. Chem. C, 2016, 120, 28519

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