MoTe2/Pentacene Type II Heterostructure for Efficient Charge Population and Extraction
Yu Jin Jang a b, Jin Cheol Park a c, Minh Dao Tran a b, Meeree Kim a d, Joonsoo Kim a c, Seok Joon Yun a b, Hyoyoung Lee a c d, Ji-Hee Kim a c, Young Hee Lee a c e
a Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), 2066 Seoburo, Jangangu, Suwon 16419, Republic of Korea
b Sungkyunkwan University, Republic of Korea, 2066 Seobu-ro, Jangan-gu, Suwon, Korea, Republic of
c Department of Energy Science, Sungkyunkwan University, 2066 Seoburo, Jangangu, Suwon 16419, Republic of Korea
d Department of Chemistry, Sungkyunkwan University, 2066 Seoburo, Jangangu, Suwon 16419, Republic of Korea
e Department of Physics, Sungkyunkwan University, 2066 Seoburo, Jangangu, Suwon 16419, Republic of Korea
nanoGe Fall Meeting
Proceedings of nanoGe Fall Meeting19 (NGFM19)
#Exciup19. Excitonic up-downconversion
Berlin, Germany, 2019 November 3rd - 8th
Organizer: Bruno Ehrler
Poster, Yu Jin Jang, 365
Publication date: 16th July 2019

Atomically-thin transition metal dichalcogenides (TMDs) are a promising platform for the next generation photovoltaics. A strong light-matter interaction ensures an efficient exciton generation and dangling-bond-free surface opens up the possibility of constructing diverse vertical van der Waals (vdW) heterostructures. Despite many attempts to improve the photoconversion efficiency, it still remains impossible to reach the maximum values which have been practically obtained to date from Si and perovskite solar cells. This raises the question of a new design of vertical heterostructures in terms of composition or configuration. Here, we propose to construct a type II heterojunction between MoTe2 and pentacene to promote the charge population and extraction. 2H-MoTe2 with a band gap of ~1 eV is ideal for solar cell performance and pentacene which undergoes a singlet fission (SF) process provides sufficient charge carriers in the heterostructure. Transient absorption spectroscopy (TAS) demonstrates not only the resonant energy transfer of triplet excitons from pentacene to A exciton band of MoTe2 but also hole transfer in opposite directions, which indicate the formation of an efficient MoTe2/pentacene type II heterojunction. In addition, the carrier density in MoTe2 is doubled in the presence of pentacene and the triplet transfer to MoTe2 consistently occurs at a delay time of ~7 ns owing to the long-lived triplet excitons in pentacene. Our observations provide the clear demonstration of triplet transfer from SF materials to TMDs and the MoTe2/pentacene type II heterostructure appears to be a breakthrough for TMD photovoltaics.

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