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Transient Optoelectronic Analysis of the Impact of Material Energetics and Recombination Kinetics on the Open-Circuit Voltage of Hybrid Perovskite Solar Cells / Scot Wheeler, Daniel Bryant, Joel Troughton, Thomas Kirchartz, Trystan Watson, Jenny Nelson, James Durrant
The Journal of Physical Chemistry C, Volume: 121, Issue: 25, Pages: 13496 - 13506
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Transient optoelectronic measurements are used to evaluate the factors determining the open-circuit voltage of a series of planar photovoltaic devices based on hybrid perovskite layers of varying iodine:bromine ratio. Employing differential charging and transient photovoltage measurements, we use a...
|Published in:||The Journal of Physical Chemistry C|
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Transient optoelectronic measurements are used to evaluate the factors determining the open-circuit voltage of a series of planar photovoltaic devices based on hybrid perovskite layers of varying iodine:bromine ratio. Employing differential charging and transient photovoltage measurements, we use a simple device model based on the charge carrier density dependence of non-geminate recombination to recreate correctly not only the measured device open-circuit voltage (VOC) as a function of light intensity, but also its dependence with bromine substitution. The 173 (±7) mV increase in device voltage observed with 20 % bromine substitution is shown to result from a 227 (±8) mV increase in effective electronic bandgap, which is offset in part by a 56 (±5) mV voltage loss due to faster carrier recombination. The faster recombination following 20% bromine substitution is avoided by ICBA (indene-C60-bisadduct) substitution into the PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) electron collection layer, resulting in a further 73 (±7) mV increase in device VOC. This is consistent with surface recombination losses at the perovskite / fullerene interface being the primary limitation on the VOC output of bromine substituted devices. This study thus presents, and experimentally validates, a simple model for the device physics underlying voltage generation in such perovskite based solar cells, and demonstrates that this approach can provide key insights into factors limiting this voltage output as function of material energetics.
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