Carbon Quantum Dots/TiO<sub>x</sub> Electron Transport Layer Boosts Efficiency of Planar Heterojunction Perovskite Solar Cells to 19.
basic_science · Level V
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- Record sourced from PubMed, PMID 28248512.
- Also identified by DOI 10.1021/acs.nanolett.6b05177.
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Abstract
In planar n-i-p heterojunction perovskite solar cells, the electron transport layer (ETL) plays important roles in charge extraction and determine the morphology of the perovskite film. Here, we report a solution-processed carbon quantum dots (CQDs)/TiO<sub>2</sub> composite that has negligible absorption in the visible spectral range, a very attractive feature for perovskite solar cells. Using this novel CQDs/TiO<sub>2</sub> ETL in conjunction with a planar n-i-p heterojunction, we achieved an unprecedented efficiency of ∼19% under standard illumination test conditions. It was found that a CQDs/TiO<sub>2</sub> combination increases both the open circuit voltage and short-circuits current density as compared to using TiO<sub>2</sub> alone. Various advanced spectroscopic characterizations including ultrafast spectroscopy, ultraviolet photoelectron spectroscopy, and electronic impedance spectroscopy elucidate that the CQDs increases the electronic coupling between the CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3-x</sub>Cl<sub>x</sub> and TiO<sub>2</sub> ETL interface as well as energy levers that contribute to electron extraction.