Abstract-Ultrafast Dynamics of Hole Injection and Recombination in Organo Metal Halide Perovskite Using Nickel Oxide as p-Type Contact Elec-Trode

Alice Corani, Ming-Hsien Li, Po-Shen Shen, Peter Chen, Tzung-Fang Guo, Amal El Nahhas, Kaibo Zheng, Arkady Yartsev, Villy Sundstrom, and Carlito S. Ponseca

J. Phys. Chem. Lett., Just Accepted Manuscript

DOI: 10.1021/acs.jpclett.6b00238

Publication Date (Web): March 4, 2016

Copyright © 2016 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/acs.jpclett.6b00238?journalCode=jpclcd

There is a mounting effort to use nickel oxide (NiO) as p-type selective electrode for organo-metal halide perovskite based solar cells. Recently, an overall power conversion efficiency using this hole acceptor has reached 18%. However, ultrafast spectroscopic investigations on the mechanism of charge injection as well as recombination dynamics have yet to be studied and understood. Using time-resolved terahertz spectroscopy, we show that hole transfer is complete on the sub-picosecond time scale, driven by the favorable band alignment between the valence bands of perovskite and NiO nanoparticles (NiO(np)). Recombination between holes injected into NiO(np) and mobile electrons in the perovskite material is shown to be hundreds of ps to few ns. Due to the low conduc-tivity of NiO(np), holes are pinned at the interface and it is electrons that determines the recombination rate. This recom-bination competes with charge collection and therefore must be minimized. Doping NiO that promotes higher mobility of holes is desirable in order to prevent back recombination.

Abstract-Electron and Hole Contributions to the Terahertz Photoconductivity of a Conjugated Polymer:Fullerene Blend Identified

 

http://pubs.acs.org/doi/abs/10.1021/jz301013u

 

Carlito S. Ponseca , Hynek Němec,  Nenad Vukmirovic , Sandra Fusco , Ergang Wang , Mats R. Andersson , Pavel Chabera , Arkady Petrovich Yartsev , and Villy Sundstrom

J. Phys. Chem. Lett., Just Accepted Manuscript

DOI: 10.1021/jz301013u

Publication Date (Web): August 17, 2012

Copyright © 2012 American Chemical Society

Time-resolved terahertz spectroscopy was employed for the investigation of charge transport dynamics in benzothiadiazolo-dithiophene polyfluorene ([2,7-(9,9-dioctyl-fluorene)-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3-benzothiadiazole)]) (APFO-3) polymers with various chain lengths and in its monomer form, all blended with an electron acceptor ([6,6]-phenyl-C61-butyric acid methyl ester, PCBM). Upon photoexcitation, charged polaron pairs are created, negative charges are transferred to fullerenes while positive polarons remain on polymers/monomers. Vastly different hole mobility in polymer and monomer blends allows us to distinguish the hole and electron contributions to the carrier mobility.