Journal of Physical Chemistry C | 2019
Effect of Surface Ligand on Charge Separation and Recombination at CsPbI3 Perovskite Quantum Dot/TiO2 Interfaces
Abstract
CsPbI3 perovskite quantum dot (QD) solar cells are a promising device platform for further development due to their improved stability compared to bulk materials. The fabrication of these devices often involves postsynthetic washing of colloidal QDs to remove surface ligands. Herein, we investigate how this postsynthetic treatment affects the charge separation (CS) and charge recombination (CR) processes at the interface of CsPbI3 QDs and the TiO2 electron extraction layer. The CS time constant at QD/TiO2 interface decrease from 457 ± 4 ps for QDs directly deposited on TiO2 to 288 ± 1 ps for QDs that were washed twice by methyl acetate, increasing the ET efficiency from 89.9 ± 0.3% to 98.3 ± 0.01%. Interestingly, this treatment also lengthens the average charge recombination time constants from 346 ± 18 ns to 1180 ± 60 ns, which is also beneficial for reducing charge recombination loss. This result demonstrates the pronounced effect of QD washing by methyl acetate (MeOAc) on interfacial charge transfer pr...