Hot Hole Transfer Dynamics from CsPbBr < inf > 3 < /inf > Perovskite Nanocrystals

Abstract

Transfer of the hot charge carriers prior to their cooling to the band-edge states can enhance the efficiency of a semiconductor-based solar cell much beyond its Shockley-Queisser (SQ) limiting value. Herein, we explore transfer of hot holes from the APbBr3 nanocrystals (NCs) employing a carefully chosen molecular system, 4-mercaptophenol. Ultrafast pump-probe and fluorescence measurements indeed confirm this transfer process, whose efficiency depends on the energy content of the hole, and a maximum efficiency of ∼43% is achieved with CsPbBr3 NCs for a photoexcitation energy of ∼1.46Eg (Eg is the band gap of the NCs). While the estimated hot hole cooling and transfer rates are quite comparable, hole transfer from the band edge is found to be a significantly slower process. The findings of the present study suggest that exceeding the SQ efficiency of the solar cells based on the perovskites can indeed be a reality.