An ion-beam surface sputtering approach to the quest for lead-free metal halide perovskite for solar cells

Metal halide perovskites have been the subject of intense theoretical and experimental research in recent years, due to their huge potential over their silicon-based counterparts for tunable optoelectronic applications in high-tech device innovation. The current best perovskite for solar cell applications, with a power conversion efficiency of 22%, methylammonium lead iodide (CH₃NH₃PbI₃), is toxic due to the presence of lead and is therefore harmful in solar cell applications despite its low concentration in solar cells. Hence, research exploits are geared towards perovskites without lead. Unfortunately, this has taken back the gains in PCEs by about 70%, and a lot is being done for improvement. In this paper, a new approach to these studies is introduced by performing Monte Carlo simulations of ion-beam sputtering of lead and tin perovskites, as well as other promising candidate materials, in order to throw some light on their potentials for higher efficiencies in photovoltaic applications. The sputtering characteristics of six promising perovskites, including lead perovskite and lead-substituted perovskites, were compared. The results showed a remarkable exhibition of similar sputtering characteristics of linear projected ion range for Pb and Sn, with a maximum sputter yield around 78° ion incidence. The results also indicated a correspondence between the sputtering characteristics and PCE.