Quantifying Quasi-Fermi Level Splitting and Mapping its Heterogeneity in Atomically Thin Transition Metal Dichalcogenides.
ADVANCED MATERIALS(2019)
摘要
One of the most fundamental parameters of any photovoltaic material is its quasi-Fermi level splitting ( increment mu) 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 WS2, MoS2, WSe2, and MoSe2-based solar cells, and they are compared with state-of-the-art perovskites. These results show that V-oc values of approximate to 1.4, approximate to 1.12, approximate to 1.06, and approximate to 0.93 V can be potentially achieved from solar cells fabricated from WS2, MoS2, WSe2, and MoSe2 monolayers at 1 Sun illumination, respectively. It is also observed that increment mu is inhomogeneous across different regions of these monolayers. Moreover, it is attempted to engineer the observed increment mu 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 increment mu heterogeneity. The values of increment mu determined from this work reveal the potential of atomically thin TMDs for high-voltage, ultralight, flexible, and eye-transparent future solar cells.
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关键词
2D materials,open-circuit voltage,photoluminescence,photovoltaic cells,quasi-Fermi level splitting,transition metal dichalcogenides
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