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

Abstract

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 $$Ag_i^ +$$ A g i + , $$Cu_i^ +$$ C u i + , and $$Au_i^ +$$ A u i + , will be formed under p-type conditions, whereas the Sn-site substitutional acceptor impurities, namely $$Au_{Sn}^{2 - }$$ A u S n 2 − , $$Ag_{Sn}^{2 - }$$ A g S n 2 − , and $$Cu_{Sn}^{2 - }$$ C u S n 2 − , are the dominant impurities, especially under n-type conditions. In particular, except for $$Au_i^ +$$ A u 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.

Atomic and Molecular Hydrogen Impurities in Hybrid Perovskite Solar Cells

“…For its Sn-based counterpart, MASnI 3 , a promising alternative for solving the toxicity of Pb, exhibits poor air stability due to the easy oxidation of Sn 2+ and possesses a rather huge defect-induced deep-trap state density, which serves as the main underlying mechanism contributing to the reduced PCE . In addition, external metal impurities induced by the electrodes, such as the commonly used Au, also contribute to device degradation. ,, …”

Hydrogen-Anion-Induced Carrier Recombination in MAPbI3 Perovskite Solar Cells

“…Significant efforts ,− have been devoted to study intrinsic point defects to reveal the possible origin of the deep-level nature in the prototypical hybrid perovskite MAPbI 3 . The contribution of the charge carrier recombination losses has to date been assigned to intrinsic iodine interstitials (I i ) ,, and hydrogen vacancies from the host nitrogen atom ( V H ( N ) – ) .…”

Coherent Hopping Transport and Giant Negative Magnetoresistance in Epitaxial CsSnBr3

“…While previous work has reported ohmic contact between CsSnBr 3 and Au at room temperature, , our two-terminal resistance measurements cannot preclude a contribution from a contact resistance between the evaporated gold and the CsSnBr 3 epilayer; however, we emphasize that such a contact resistance would not change the conclusions we draw regarding coherent hopping transport described below. We also note that recent theoretical work has indicated the potential role of electrode induced impurities in CsSnBr 3 , which could be investigated with future four-terminal devices. Finally, we note that all measurements reported here were performed in a regime of linear response, which was ensured by performing device IV characteristics at the lowest temperatures.…”