Direct observation of dramatically enhanced hole formation in a perovskite-solar-cell material spiro-OMeTAD by Li-TFSI doping
Kazuhiro Marumoto a, Miki Namatame a, Yuhei Ogomi b, Shuzi Hayase b
a University of Tsukuba
b Kyushu Institute of Technology, Japan, 204 Hibikino Wakamatsu-ku, Kitakyushu - Fukuoka, 808, Japan
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of International Conference Asia-Pacific Hybrid and Organic Photovoltaics 2018 (AP-HOPV18)
Kitakyūshū-shi, Japan, 2018 January 28th - 30th
Organizers: Shuzi Hayase, Juan Bisquert and Hiroshi Segawa
Poster, Kazuhiro Marumoto, 042
Publication date: 27th October 2017

Electron spin resonance (ESR) spectroscopy of 2,2´,7,7´-tetrakis-(N,N-di-p-methoxyphenylamine)9,9´-spirobifluorene (spiro-OMeTAD) thin films and perovskite (CH3NH3PbI3)/spiro-OMeTAD layered films are reported [1,2]. Clear ESR signals (g = 2.0030) were observed by adding a dopant lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) to the spiro-OMeTAD thin films, which directly showed the spin (hole) formation in spiro-OMeTAD by the Li-TFSI doping. The number of spins in the spiro-OMeTAD thin film increased by more than two orders of magnitude by the Li-TFSI doping under dark conditions, which demonstrates from a microscopic viewpoint that Li-TFSI has high doping effects for the spiro-OMeTAD thin films. Under simulated solar irradiation, the spin density in the spiro-OMeTAD thin films and the perovskite/spiro-OMeTAD layered films largely increased by the Li-TFST doping due to the formation of long-lived holes in spiro-OMeTAD. The transient responses of the number of photogenerated spins, Nspin, of the layered films upon the light irradiation showed the increase and the decrease in the Nspin due to the hole transfer and recombination at the perovskite/spiro-OMeTAD interface. The states of long-lived holes in the spiro-OMeTAD layers were analyzed using the simulation of the ESR spectra, which reveals the mobile photogenerated holes with a lifetime >10 μs.

[1] Applied Physics Letters 110(12) (2017) 123904-1-5. (DOI:10.1063/1.4977789) (APL Editor's Pick)

[2] Revealing the Microscopic Mechanisms in Perovskite Solar Cells (AIP Publishing press release, WASHINGTON, D.C., March 21, 2017)

 

© FUNDACIO DE LA COMUNITAT VALENCIANA SCITO
We use our own and third party cookies for analysing and measuring usage of our website to improve our services. If you continue browsing, we consider accepting its use. You can check our Cookies Policy in which you will also find how to configure your web browser for the use of cookies. More info