Transientoptoelectronicanalysis of the impact of material energetics and recombination kinetics on the open-circuit voltage of hybridperovskite solar cells

Abstract Click to copy section link Section link copied! High Resolution Image Download MS PowerPoint Slide Transient optoelectronic measurements were used to evaluate the factors determining the open-circuit voltage of a series of planar photovoltaic devices based on hybrid perovskite layers with varying iodine/bromine ratios. Employing differential charging and transient photovoltage measurements, we used a simple device model based on the charge-carrier-density dependence of nongeminate recombination to re-create correctly not only the measured device open-circuit voltage ( V OC ) as a function of light intensity but also its dependence on 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 band gap, which was offset in part by a 56 (±5) mV voltage loss due to faster carrier recombination.

The faster recombination following 20% bromine substitution can be avoided by indene–C 60 bisadduct (ICBA) substitution into the [6, 6]-phenyl-C 61 -butyric acid methyl ester (PCBM) electron-collection layer, resulting in a further 73 (±7) mV increase in device V OC . These results are consistent with surface recombination losses at the perovskite/fullerene interface being the primary limitation on the V OC 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 a function of material energetics. ACS Publications Copyright © 2017 American Chemical Society Subjects what are subjects Article subjects are automatically applied from the ACS Subject Taxonomy and describe the scientific concepts and themes of the article.

Electrical properties Layers Light Perovskites Recombination