Hot Hole Transfer Dynamics from CsPbBr3 Perovskite Nanocrystals

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 Shocldey-Queisser (SQ) limiting value. Herein, we explore transfer of hot holes from the APbBr(3) 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 similar to 43% is achieved with CsPbBr3 NCs for a photoexcitation energy of similar to 1.46E(g) (E-g 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.