Boosting the Efficiency of Perovskite Solar Cells with CsBr‐Modified Mesoporous TiO₂ Beads as Electron‐Selective Contact

Abstract

Abstract Rapid extraction of photogenerated charge carriers is essential to achieve high efficiencies with perovskite solar cells (PSCs). Here, a new mesoscopic architecture as electron‐selective contact for PSCs featuring 40 nm sized TiO 2 beads endowed with mesopores of a few nanometer diameters is introduced. The bimodal pore distribution inherent to these films produces a very large contact area of 200 m 2 g −1 whose access by the perovskite light absorber is facilitated by the interstitial voids between the particles. Modification of the TiO 2 surface by CsBr further strengthens its interaction with the perovskite. As a result, photogenerated electrons are extracted rapidly producing a very high fill factor of close to 80% a V OC of 1.14 V and a PCE up to 21% with negligible hysteresis.