In Situ Ligand Bonding Management of CsPbI₃ Perovskite Quantum Dots Enables High‐Performance Photovoltaics and Red Light‐Emitting Diodes

Abstract

To fine-tune surface ligands towards high-performance devices,wedeveloped an in situ passivation process for all-inorganic cesium lead iodide (CsPbI 3)perovskite quantum dots (QDs) by using ab ifunctional ligand, L-phenylalanine (L-PHE). Through the addition of this ligand into the precursor solution during synthesis,the in situ treated CsPbI 3 QDs displays ignificantly reduced surface states,i ncreased vacancy formation energy,h igher photoluminescence quantum yields, and muchi mproved stability.C onsequently,t he L-PHE passivated CsPbI 3 QDs enabled the realization of QD solar cells with an optimal efficiency of 14.62 %a nd red light-emitting diodes (LEDs) with ah ighest external quantum efficiency (EQE) of 10.21 %, respectively,d emonstrating the great potential of ligand bonding management in improvingt he optoelectronic properties of solution-processed perovskite QDs.

Polymeric Hole Transport Materials for Red CsPbI3 Perovskite Quantum-Dot Light-Emitting Diodes

“…In 2015, size-controlled and compositioncontrolled CsPbX 3 quantum dots (QDs) were first synthesized using a colloidal method [5]. The colloidal CsPbX 3 QDs exhibit high color purity in photoluminescence (PL) spectrum, and photoluminescence quantum yields (PLQYs) as high as 100%, which makes them candidates for light-emitting diodes (LEDs) [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] and solar cells [22][23][24][25][26][27][28]. Up until now, the development of the colloidal synthesis has been simultaneously promoted in parallel with the performance of CsPbX3 QDs-based optoelectronic devices.…”

“…All-inorganic perovskite QD-based LEDs (IPQLEDs) have drawn much attention for their solution-processed fabrication and more flexible application [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. To improve the IPQLED performance, highly efficient exciton recombination in the QD films is a Polymers 2021, 13, 896 2 of 10 significantly critical issue.…”

“…Subsequently, PVK was replaced with Poly(N,N -bis-4-butylphenyl-N,N -bisphenyl)benzidine (Poly-TPD), because of improved hole injection efficiency, which could be attributed to the hole mobility of Poly-TPD by about two orders of magnitude higher than that of PVK [8]. To date, Poly-TPD has been selected as the hole transporting material in most of IPQLED studies [12][13][14][15][16][17][18][19][20][21]. Poly(triaryl)amine (PTAA) also shows a high hole mobility, which makes it another good choice for the hole transporting materials.…”

CsPbI3 perovskite quantum dot solar cells: opportunities, progress and challenges

“…This result was supported by density functional theory (DFT), which shows a stronger bonding between the L-PHE and CsPbI 3 QDs surface relative to native ligands. This is visualized in Fig.3d 107. In this process, by removing the longchain native ligands which are involved in the QDs purification and film preparation, degeneration of ions occurs, leaving behind defects on the surface 61,108.…”

“…60 (c) Schematic diagram of ligand exchange process for the formation of GA-matrix-capped CsPbI3 QD solids by thermal annealing induced by guanidinium thiocyanate (GASCN). 106 (d) Schematic illustration of CsPbI 3 QDs surface and theoretically calculated adsorption energy of different ligands (OLA, OA and L-PHE) using DFT application on pure CsPbI 3 QD surface 107.…”