Fundamental efficiency limit of lead iodide perovskite solar cells

Lead\nhalide materials have seen a recent surge of interest from\nthe photovoltaics community following the observation of surprisingly\nhigh photovoltaic performance, with optoelectronic properties similar\nto GaAs. This begs the question: What is the limit for the efficiency\nof these materials? It has been known that under 1-sun illumination\nthe efficiency limit of crystalline silicon is ∼29%, despite\nthe Shockley–Queisser (SQ) limit for its bandgap being ∼33%:\nthe discrepancy is due to strong Auger recombination. In this article,\nwe show that methyl ammonium lead iodide (MAPbI<sub>3</sub>) likewise\nhas a larger than expected Auger coefficient. Auger nonradiative recombination\ndecreases the theoretical external luminescence efficiency to ∼95%\nat open-circuit conditions. The Auger penalty is much reduced at the\noperating point where the carrier density is less, producing an oddly\nhigh fill factor of ∼90.4%. This compensates the Auger penalty\nand leads to a power conversion efficiency of 30.5%, close to ideal\nfor the MAPbI<sub>3</sub> bandgap.