Improving Charge Carrier Delocalization in Perovskite Quantum Dots by Surface Passivation with Conductive Aromatic Ligands

Abstract

Long-chain saturated hydrocarbons and alkoxysilanes are ligands that are commonly used to passivate perovskite quantum dots (PQDs) to enhance their stability and optical properties. However, the insulating nature of these capping ligands creates an electronic energy barrier and impedes interparticle electronic coupling, thereby limiting device applications. One strategy to solve this problem is the use of short conductive aromatic ligands that allow delocalization of the electronic wave function from the PQDs, which, in turn, facilitates charge transport between PQDs by lowering the energy barrier. This is demonstrated with methylammonium lead bromide (MAPbBr 3 ) QDs prepared using benzylamine (BZA) and benzoic acid (BA) capping ligands. Optimized BZA-BA-MAPbBr 3 QDs are highly stable and show very high photoluminescence (PL) quantum yield (QY) (86%). More importantly, the BZA-BA-MAPbBr 3 QD film exhibits higher conductivity and carrier lifetime and more efficient charge extraction compared to PQDs with insulating ligands, as indicated by electrochemical measurements and transient photocurrent and photovoltage spectroscopy.

Surface Ligand Engineering for CsPbBr3 Quantum Dots Aiming at Aggregation Suppression and Amplified Spontaneous Emission Improvement

“…Comparatively, the evident precipitation is existing in the OAm-CsPbBr 3 QDs solution, indicating a serious aggregation and degradation phenomenon has occurred owing to the surface ligand loss and damage. [11,27] The different stability of CsPbBr 3 QDs can be affected by different lengths of ligands, which is related to the strength of the VDW interactions among the ligands, and the strength is dominant to determine the crystalline structure and the optical properties of QDs. Besides, the improved stability of OLA-CsPbBr 3 QDs can also be ascribed to the short branched chains, which will increase the binding energy between the ligands and QDs and further improve the stability of CsPbBr 3 QDs.…”

“…Hence, the binding energy between the long chain capping ligands and perovskite NCs is relatively weak, which could induce nonradiative recombination of excitons and make the photoluminescence (PL) degradation. [25][26][27][28][29] For instance, phenethylamine (PEA) with shorter chain ligand was used to synthesis CsPbBr 3 QDs with the enhanced PLQY (93%), and didodecyl dimethyl ammonium bromide (DDAB) was adopted to improve the PLQY of perovskite NCs to be 96%. In addition, the PLQY and stability in air of CsPbBr 3 QDs passivated by quaternary ammonium bromides (R 4 NBr) were enhanced to 100% ± 5% and 21 days, respectively.…”

Tailored PEDOT:PSS hole transport layer for higher performance in perovskite solar cells: Enhancement of electrical and optical properties with improved morphology

“…Metal halide perovskites have emerged as a promising photovoltaic technology due to their solution processibility, low fabrication costs, high power conversion efficiency and rapid energy payback time [1][2][3][4][5][6] . Due to excellent light absorption, devices.…”

Nanoscale control of grain boundary potential barrier, dopant density and filled trap state density for higher efficiency perovskite solar cells

“…Perovskite solar cells (PSC) have attracted remarkable attention owing to their interesting material properties of metal‐organic halide perovskites such as high absorption coefficients, tunable optical band gap, long range carrier diffusion lengths (100‐1000 nm), small exciton binding energy, and ambipolar charge transport . The power conversion efficiency (PCE) of perovskite‐based solar cells has increased drastically during the past several years .…”

“…Perovskite solar cells (PSC) have attracted remarkable attention owing to their interesting material properties of metal-organic halide perovskites such as high absorption coefficients, tunable optical band gap, long range carrier diffusion lengths (100-1000 nm), small exciton binding energy, and ambipolar charge transport. [1][2][3][4][5][6][7][8] The power conversion efficiency (PCE) of perovskite-based solar cells has increased drastically during the past several years. [9][10][11][12][13] Organolead halide perovskite materials have been used as the active material in a range of optoelectronic device based applications such as light emitting devices, photodetectors etc.…”