Electrode-induced impurities in tin halide perovskite solar cell material CsSnBr3 from first principles

All-inorganic lead-free CsSnBr3 is attractive for applications in solar cells due to its nontoxicity and stability, but the device performance to date has been poor. Besides the intrinsic properties, impurities induced from electrodes may significantly influence the device performance. Here, we systematically studied the stability, transition energy levels, and diffusion of impurities from the most commonly used electrodes (Au, Ag, Cu, graphite, and graphene) in CsSnBr3 based on density functional theory calculations. Our results reveal that, whereas graphite and graphene electrodes exhibit negligible influence on CsSnBr3 due to the relatively high formation energies for carbon impurities in CsSnBr3, atoms from the metal electrodes can effectively diffuse into CsSnBr3 along interstice and form electrically active impurities in CsSnBr3. In this case, a significant amount of donor interstitial impurities, such as Ag-i(+), Cu-i(+), and Au-i(+), will be formed under p-type conditions, whereas the Sn-site substitutional acceptor impurities, namely Au-Sn(2-), Ag-Sn(2-), and Cu-Sn(2-), are the dominant impurities, especially under n-type conditions. In particular, except for Au-i(+), all these major impurities from the metal electrodes act as nonradiative recombination centers in CsSnBr3 and significantly degrade the device performance. Our work highlights the distinct behaviors of the electrode impurities in CsSnBr3 and their influence on the related devices and provides valuable information for identifying suitable electrodes for optoelectronic applications.

Automated summary

In this study, the stability, transition energy levels, and diffusion of impurities from commonly used electrodes in CsSnBr3 were systematically investigated using density functional theory calculations. It was found that impurities from metal electrodes can effectively diffuse into CsSnBr3 and degrade device performance, serving as nonradiative recombination centers. This research provides valuable insights for identifying suitable electrodes for optoelectronic applications.