Abstract
AbstractHalide double perovskites have gained significant attention, owing to their composition of low‐toxicity elements, stability in air, and recent demonstrations of long charge‐carrier lifetimes that can exceed 1 µs. In particular, Cs2AgBiBr6 is the subject of many investigations in photovoltaic devices. However, the efficiencies of solar cells based on this double perovskite are still far from the theoretical efficiency limit of the material. Here, the role of grain size on the optoelectronic properties of Cs2AgBiBr6 thin films is investigated. It is shown through cathodoluminescence measurements that grain boundaries are the dominant nonradiative recombination sites. It also demonstrates through field‐effect transistor and temperature‐dependent transient current measurements that grain boundaries act as the main channels for ion transport. Interestingly, a positive correlation between carrier mobility and temperature is found, which resembles the hopping mechanism often seen in organic semiconductors. These findings explain the discrepancy between the long diffusion lengths >1 µm found in Cs2AgBiBr6 single crystals versus the limited performance achieved in their thin film counterparts. This work shows that mitigating the impact of grain boundaries will be critical for these double perovskite thin films to reach the performance achievable based on their intrinsic single‐crystal properties.
Highlights
Introduction result was achieved with aCs2AgBiBr6 thin film absorber, which is the halide double perovskite that has been investigated the Inspired by the tremendous success of the lead-halide perov- most for photovoltaic applications.[8,13,14,15,16] But even considering skites, there has been a resurgence of interest in halide elpaso- its large and indirect bandgap of 2.25 eV, the current efficiency lites, or double perovskites, over the past five years.[1,2,3,4,5] Double record is still three times lower than the spectroscopic limitedZ
The differences between the crystallite and microfeature sizes found from X-ray diffraction (XRD) versus scanning electron microscopy (SEM) measurements may have been due to the microfeatures in SEM being composed of several crystallites, because of a variation in grain size and the narrower XRD peaks from the larger grains being hidden behind the broader peaks from the smaller grains, or because the XRD peaks were broadened due to other factors, such as stacking faults
We found that grain boundaries are the dominant nonradiative recombination sites and act as the main channel for ion migration
Summary
Cs2AgBiBr6 thin films were synthesized by solution processing, as detailed in the Experimental Section. The crystallite sizes obtained by fitting the XRD peaks were 72 ± 7 nm (0.3 m), 98 ± 7 nm (0.4 m), and 113 ± 3 nm (0.5 m), as shown in Figure 1c (details in the Supporting Information) We hereafter refer to the films based on the concentration of the precursor solution they were deposited from (rather than their XRD or SEM grain/microfeature size)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
