CO2 doping of organic interlayers for perovskite solar cells

Jaemin Kong, Yongwoo Shin, Jason A. Röhr, Hang Wang, Juan Meng, Yueshen Wu, Adlai Katzenberg, Geunjin Kim, Dong Young Kim, Tai De Li, Edward Chau, Francisco Antonio, Tana Siboonruang, Sooncheol Kwon, Kwanghee Lee, Jin Ryoun Kim, Miguel A. Modestino, Hailiang Wang, André D. Taylor

Research output: Contribution to journalArticlepeer-review

Abstract

In perovskite solar cells, doped organic semiconductors are often used as charge-extraction interlayers situated between the photoactive layer and the electrodes. The π-conjugated small molecule 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9-spirobifluorene (spiro-OMeTAD) is the most frequently used semiconductor in the hole-conducting layer1–6, and its electrical properties considerably affect the charge collection efficiencies of the solar cell7. To enhance the electrical conductivity of spiro-OMeTAD, lithium bis(trifluoromethane)sulfonimide (LiTFSI) is typically used in a doping process, which is conventionally initiated by exposing spiro-OMeTAD:LiTFSI blend films to air and light for several hours. This process, in which oxygen acts as the p-type dopant8–11, is time-intensive and largely depends on ambient conditions, and thus hinders the commercialization of perovskite solar cells. Here we report a fast and reproducible doping method that involves bubbling a spiro-OMeTAD:LiTFSI solution with CO2 under ultraviolet light. CO2 obtains electrons from photoexcited spiro-OMeTAD, rapidly promoting its p-type doping and resulting in the precipitation of carbonates. The CO2-treated interlayer exhibits approximately 100 times higher conductivity than a pristine film while realizing stable, high-efficiency perovskite solar cells without any post-treatments. We also show that this method can be used to dope π-conjugated polymers.

Original languageEnglish (US)
Pages (from-to)51-56
Number of pages6
JournalNature
Volume594
Issue number7861
DOIs
StatePublished - Jun 3 2021

ASJC Scopus subject areas

  • General

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