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Quantifying Quasi‐Fermi Level Splitting and Mapping its Heterogeneity in Atomically Thin Transition Metal Dichalcogenides
Author(s) -
Tebyetekerwa Mike,
Zhang Jian,
Liang Kun,
Duong The,
Neupane Guru Prakash,
Zhang Linglong,
Liu Boqing,
Truong Thien N.,
Basnet Rabin,
Qiao Xiaojing,
Yin Zongyou,
Lu Yuerui,
Macdonald Daniel,
Nguyen Hieu T.
Publication year - 2019
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.201900522
Subject(s) - monolayer , materials science , semiconductor , solar cell , transition metal , optoelectronics , fermi level , photovoltaic system , thin film , doping , open circuit voltage , nanotechnology , voltage , catalysis , ecology , biochemistry , chemistry , physics , quantum mechanics , electron , biology
One of the most fundamental parameters of any photovoltaic material is its quasi‐Fermi level splitting (∆ µ ) under illumination. This quantity represents the maximum open‐circuit voltage ( V oc ) that a solar cell fabricated from that material can achieve. Herein, a contactless, nondestructive method to quantify this parameter for atomically thin 2D transition metal dichalcogenides (TMDs) is reported. The technique is applied to quantify the upper limits of V oc that can possibly be achieved from monolayer WS 2 , MoS 2 , WSe 2 , and MoSe 2 ‐based solar cells, and they are compared with state‐of‐the‐art perovskites. These results show that V oc values of ≈1.4, ≈1.12, ≈1.06, and ≈0.93 V can be potentially achieved from solar cells fabricated from WS 2 , MoS 2 , WSe 2 , and MoSe 2 monolayers at 1 Sun illumination, respectively. It is also observed that ∆ µ is inhomogeneous across different regions of these monolayers. Moreover, it is attempted to engineer the observed ∆ µ heterogeneity by electrically gating the TMD monolayers in a metal‐oxide‐semiconductor structure that effectively changes the doping level of the monolayers electrostatically and improves their ∆ µ heterogeneity. The values of ∆ µ determined from this work reveal the potential of atomically thin TMDs for high‐voltage, ultralight, flexible, and eye‐transparent future solar cells.