Abstract
Perovskite photovoltaic (PV) cells have demonstrated power conversion efficiencies (PCE) that are close to those of monocrystalline silicon cells; however, in contrast to silicon PV, perovskites are not limited by Auger recombination under 1-sun illumination. Nevertheless, compared to GaAs and monocrystalline silicon PV, perovskite cells have significantly lower fill factors due to a combination of resistive and non-radiative recombination losses. This necessitates a deeper understanding of the underlying loss mechanisms and in particular the ideality factor of the cell. By measuring the intensity dependence of the external open-circuit voltage and the internal quasi-Fermi level splitting (QFLS), the transport resistance-free efficiency of the complete cell as well as the efficiency potential of any neat perovskite film with or without attached transport layers are quantified. Moreover, intensity-dependent QFLS measurements on different perovskite compositions allows for disentangling of the impact of the interfaces and the perovskite surface on the non-radiative fill factor and open-circuit voltage loss. It is found that potassium-passivated triple cation perovskite films stand out by their exceptionally high implied PCEs > 28%, which could be achieved with ideal transport layers. Finally, strategies are presented to reduce both the ideality factor and transport losses to push the efficiency to the thermodynamic limit.
Highlights
Perovskite photovoltaic (PV) cells have demonstrated power conversion efficiencies (PCE) that are close to those of monocrystalline silicon cells; in contrast to silicon PV, perovskites are not limited by Auger recombination under 1-sun illumination
With respect to single-junction perovskite solar cells, the efficiency increased from 3.9% to 25.2%[10] within only 10 years and monolithic silicon/perovskite tandem cells reached up to 29.1% power conversion efficiency within an arguably even shorter
For a potassium-passivated triple cation perovskite film, we found an even higher efficiency potential exceeding 28% which could be achieved if non-radiative interfacial recombination and charge transport losses could be overcome
Summary
0.018 phenomena are always an important consideration in perovskite solar cells.[52,53,54,55,56] in order to correlate the optical and the electrical measurements, we performed the intensitydependent QFLS measurements for different exposure times, ranging from 0.4 s to 30 s at each measured data point which is relevant for the typical timescales of JV-scans. In this regard, it is interesting to note that the PLQY of the TOPO-passivated 83–17 triple cation film is as high as 22.6% as compared to 0.8% of the unpassivated film. This PLQY enhancement is similar to previous results where TOPO was applied on top of MAPI,[36,57] indicating that TOPO passivates similar surface defects in case of (83–17) triple
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