Ligand exchange engineering of FAPbI3 perovskite quantum dots for solar cells

Abstract

Formamidinium lead triiodide (FAPbI3) perovskite quantum dots (PQDs) show great advantages in photovoltaic applications due to their ideal bandgap energy, high stability and solution processability. The anti-solvent used for the post-treatment of FAPbI3 PQD solid films significantly affects the surface chemistry of the PQDs, and thus the vacancies caused by surface ligand removal inhibit the optoelectronic properties and stability of PQDs. Here, we study the effects of different anti-solvents with different polarities on FAPbI3 PQDs and select a series of organic molecules for surface passivation of PQDs. The results show that methyl acetate could effectively remove surface ligands from the PQD surface without destroying its crystal structure during the post-treatment. The benzamidine hydrochloride (PhFACl) applied as short ligands of PQDs during the post-treatment could fill the A-site and X-site vacancies of PQDs and thus improve the electronic coupling of PQDs. Finally, the PhFACl-based PQD solar cell (PQDSC) achieves a power conversion efficiency of 6.4%, compared to that of 4.63% for the conventional PQDSC. This work provides a reference for insights into the surface passivation of PQDs and the improvement in device performance of PQDSCs. Graphical abstract

Synergetic Effect of Aluminum Oxide and Organic Halide Salts on Two‐Dimensional Perovskite Layer Formation and Stability Enhancement of Perovskite Solar Cells

“…This indicates the possibility of compensation for decomposed FA or protection of FA due to post-treatment. [26] Furthermore, the peaks at 2851 , 2923, and 2959 cm −1 highlighted by the pink dotted line, were identified for the OAI-and OAI/AlO xtreated perovskite, supporting the existence of octylammonium (OA) cations on the surface, [27] which is consistent with the additional peak of C─N bonding detected in the case of the OAI-and OAI/AlO x -treated perovskite as shown in Figure 2b. In addition, the Pb 4f 5/2 and Pb 4f 7/2 peaks located at 143.1 and 138.25 eV shifted to lower binding energies of 142.92 and 138.0 eV, respectively, which was indicative of the interaction between nitrogen with lone electron pair [28] in the OAI molecule and uncoordinated lead at the surface of the perovskite.…”

Perovskite Colloidal Quantum Dots with Tailored Properties: Synthesis Strategies and Photovoltaic Applications

“…Thus, the formation of surface defects was effectively reduced and a halide-rich surface was obtained, resulting in a power conversion efficiency of 13.8% . Similarly, to improve the efficiency and stability of Pe-CQDs photovoltaics, researchers have focused on substituting long alkyl chain ligands with short alkyl chain ligands, which increases the carrier mobility and passivates the surface defects of Pe-CQDs . However, the inherent lattice distortion, which is a fundamental factor hindering carrier mobility within Pe-CQDs solids, is still not resolved.…”