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Abstract
The origins of recombination processes, particularly those that relate to current–voltage hysteresis, are still unclear in perovskite solar cells. Of particular interest is the impact different contact materials have on the level of hysteresis observed. This work shows that there is a clear link between ionic movement and interfacial recombination, which have both been shown to be responsible for hysteresis. When low-temperature transient photovoltage (TPV) measurements are performed over a period in which ions redistribute within the perovskite layer, the dominant recombination mechanism, responsible for hysteresis and other slow dynamic processes, is found to occur at the TiO2/perovskite interface. We observe an anomalous negative transient upon firing the laser pulse, which we attribute to interfacial recombination at the TiO2/perovskite interface. The impact of recombination at the perovskite/HTL interface is shown to be negligible by performing TPV measurements using different laser wavelengths to pr...
Highlights
The origins of recombination processes, those that relate to current−voltage hysteresis, are still unclear in perovskite solar cells
One of the key curiosities encountered in the field is the hysteresis exhibited in the current−voltage (I−V) curves of perovskite devices
We demonstrate the influence of different contact materials on ion migration and recombination within perovskite solar cells using transient photovoltage (TPV) decay measurements
Summary
Letter that light-induced polarization of perovskite devices occurs and that anomalies in the TPV decay traces can be explained via the build-up and discharge of mobile ions affecting interfacial recombination processes, predominantly at the TiO2/perovskite interface. Modeling and experimental results have shown that hysteresis (and associated slow dynamic processes) is linked to ion migration within the perovskite layer and the impact these ions have on recombination at the interfaces with chargeselective contacts.[13,20,33,35] A interesting observation is the slow rise in open-circuit voltage, from a dark equilibrium starting condition, upon illumination This suggests an initial high rate of recombination, which leads to a suppression of the measured Voc. The slow increase to a steady-state Voc has been shown to be linked to ionic movement and suggests that the rate of recombination is reduced as ions migrate.[20,33] The issue with many time and frequency domain electrical characterization techniques is that they often rely on the device being at a steady state.
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