D. Meggiolaro, D. Ricciarelli, Ahmed A. Alasmari
Apr 16, 2020
Citations
0
Influential Citations
100
Citations
Quality indicators
Journal
The journal of physical chemistry letters
Abstract
Tin-halide perovskites are the only lead-free material class endowed with comparable optoelectronic properties to lead-iodide perovskites. Despite significant progress, the device efficiency and stability of tin-halide perovskites is still limited by two potentially related phenomena, i.e. self p-doping and tin oxidation. Both processes are likely related to defects, thus understanding tin-halide defect chemistry is a key step towards exploitation of this materials class. We investigate the MASnI3 perovskite defect chemistry, as a prototype of the entire materials class, based on state of the art density functional theory simulations. We show that the inherently low ionization potential of MASnI3 is solely responsible of the high stability of tin vacancy and interstitial iodine defects, which are in turn at the origin of the material p-doping. Tin vacancies create a locally iodine-rich environment which could promote the Sn(II) Sn(IV) oxidation. The higher band edge energies of MASnI3 compared to MAPbI3 lead also to the emergence of deep electron traps associated to under-coordinated tin defects (e.g. interstitial tin) and the suppression of deep transitions associated to under-coordinated iodine defects which are typical of MAPbI3. Thus, while lead-iodide perovskites are dominated by iodine chemistry, tin chemistry dominates tin-iodide perovskites defect chemistry, with mixed tin-lead perovskites showing an intermediate behavior. Mixed tin/lead perovskites exhibit an intermediate behavior and are predicted to be potentially free of deep traps. Compositional alloying with different metals is finally explored as a strategy to mitigate defect formation and self p-doping in tin iodide perovskites.