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Ion Movement Explains Huge V OC Increase despite Almost Unchanged Internal Quasi‐Fermi‐Level Splitting in Planar Perovskite Solar Cells
Author(s) -
Herterich Jan,
Unmüssig Moritz,
Loukeris Georgios,
Kohlstädt Markus,
Würfel Uli
Publication year - 2021
Publication title -
energy technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.91
H-Index - 44
eISSN - 2194-4296
pISSN - 2194-4288
DOI - 10.1002/ente.202001104
Subject(s) - passivation , perovskite (structure) , photoluminescence , ion , materials science , perovskite solar cell , fermi level , intensity (physics) , analytical chemistry (journal) , ionic bonding , optoelectronics , energy conversion efficiency , chemistry , optics , nanotechnology , physics , crystallography , layer (electronics) , organic chemistry , quantum mechanics , chromatography , electron
Light soaking under “1 sun” is performed on planar p–i–n perovskite solar cells with a Cs 0.05 MA 0.10 FA 0.85 Pb(I 0.95 Br 0.05 ) 3 absorber while measuring current and voltage transients simultaneously to spectral photoluminescence (PL). From theory a tenfold increase in PL intensity is expected for every 60 mV rise in V OC (at 300 K). However, the solar cells investigated show a reversible V OC increase from as low as 0.5 up to 1.05 V during light soaking, whereas the PL intensity hardly changes. A model is developed based on mobile ions in combination with a nonideal contact. It reproduces the decoupling of the V OC and PL as well as the transient behavior in great detail. Using state‐of‐the‐art materials and passivation layers shows that light soaking is still a relevant feature of high‐efficiency perovskite solar cells. The ionic liquid additive 1‐butyl‐3‐methylimidazolium tetrafluoroborate slows down the light‐soaking behavior, giving an example of how ionic motion in perovskite solar cells can be influenced.