A bromide substituted 2D additive for stable and efficient perovskite photovoltaics.

In this article, a bromide substituted 2D layered perovskite having a repeated vertical orientation and coexisting with the bulk of a 3D perovskite is reported for the first time. This novel structure is obtained through controlled compositional engineering of the perovskite precursor solution. The photovoltaic performance of this novel 2D/3D perovskite was higher than that of 3D MAPbI 3 and a maximum photoconversion efficiency (PCE) of 17.4% was achieved. The devices fabricated using this perovskite heterostructure were stable and retained their initial PCE up to 20 days when kept open in a laboratory environment with 40% relative humidity.