Colloidal Nanocrystals as a Platform for Rapid Screening of Charge Trap Passivating Molecules for Metal Halide Perovskite Thin Films

Abstract

Charge recombination at surface trap sites is a significant impediment to metal halide perovskite (MHP) thin film-based optoelectronic devices. To passivate the surface charge traps, chemical treatments with molecules that bind to the MHP thin film surfaces can be employed. However, the current approaches to test the trap passivation efficacy of molecules on thin film surface suffer from limited through-put and low statistical significance. Here, we demonstrate the use of colloidal MHP nanocrystals (NCs) as an experimental platform for high-throughput screening of charge trap passivating molecules for MHP thin films. Using CsPbX3 (X = Br, I) NCs, over 20 molecules were rapidly screened for their surface trap passivation efficacy. Our approach identified trin-butylphosphine (TBPh) as a superb charge trap passivating molecule on MHP surfaces. TBPh treatment brings the photoluminescence quantum yield of CsPbBr3 NCs to near unity and also results in superior surface trap passivation of MHP thin films, even when compared to a previously reported treatment with pyridine. Our work highlights the benefits of utilizing the high surface area-to-volume ratio of NCs for the accelerated study of surface trap passivation using molecular treatment and then translating the findings to bulk semiconductors. This approach is broadly applicable to a wide range of semiconductors as long as they can be synthesized into NCs.

Review of Novel Passivation Techniques for Efficient and Stable Perovskite Solar Cells

“…Other hydrophobic organic materials such as alkyl ammonium functional group, graphene derivatives, poly(methyl methacrylate) (PMMA), bathocuproine (BCP), fatty acid, polystyrene (PS), P3HT, colloidal nanocrystals, or other polymers have also been used for passivating perovskite and have been shown to be effective moisture barriers. Figure e illustrates the passivation of ionic defects in perovskite by quaternary ammonium halides (QAHs) by Zeng et al improving efficiency and stability of PSCs .…”

Design Principles for Trap-Free CsPbX3 Nanocrystals: Enumerating and Eliminating Surface Halide Vacancies with Softer Lewis Bases

“…Alternatively, oleyl­ammonium can bind surface halides through an addition mechanism. The literature on surface passivation of lead halide perovskite materials is growing rapidly, with a wide variety of chemical species having been shown to improve photo­luminescence. ,− Here, we seek to unify these findings through a molecular-level understanding of surface trap passivation in CsPbX 3 nanocrystals; this requires a combined experimental and theoretical investigation of their surface chemistry.…”

Mechanistic Exploration of Dodecanethiol-Treated Colloidal CsPbBr3 Nanocrystals with Photoluminescence Quantum Yields Reaching Near 100%

“…Adding additional surface ligands to the precursor solution can produce more stable CsPbX 3 NCs with high Φ PL . For example, tri- n -butylphosphine (PBu 3 ), tri- n -octylphosphine oxide (TOPO), primary amines (L-type ligands), (3-aminopropyl)­triethoxysilane (APS), and 3-( N , N -dimethyloctadecylammonio)­propanesulfonate ( sulfobetaine) were shown to enhance PL properties of CsPbX 3 NCs in ligand-mediated syntheses. ,, …”