Understanding the Synthetic Pathway to Large Area, High Quality [AgSePh] Nanocrystal Films

TL;DR

This study develops a controlled synthesis method for high-quality, large-area [AgSePh] nanocrystal films, enabling their use in optoelectronic devices like UV photodetectors with improved phase purity and film morphology.

Contribution

It introduces a detailed synthesis process controlling the formation of phase pure [AgSePh] nanocrystal films with tunable morphology and demonstrates their potential in large-area optoelectronic applications.

Findings

Reaction completes within 30 min at 90°C in a supersaturated PhSeH/N2 atmosphere.

Absence of precursor leftovers or oxidized species reduces intra-gap states.

High-quality centimeter-scale films suitable for UV photodetection applications.

Abstract

Silver benzeneselenolate [AgSePh] is a coordination polymer that hosts a hybrid quantum well structure. The recent advancements in the study of its tightly bound excitons (~300 meV) and photoconductive properties (recently employed in UV photodetection) makes it an interesting representative of a material platform that is an environmentally stable alternative to 2D metal halide perovskites in terms of optoelectronic properties. To this aim, several challenges are to be addressed, among which the lack of control over the metal-organic reaction process in the reported synthesis of the [AgSePh] nanocrystal film (NC). This issue contributed to cast doubts over the origin of its intra-bandgap electronic states. In this article we study all the steps to obtain phase pure [AgSePh] NC films, from thin silver films through its oxidation and reaction via a chemical vapor-solid with benzeneselenol, by means of UV-vis, XRD, SEM, and AFM. Raman and FTIR spectroscopy are also employed to provide vibrational peaks assignment, for the first time on this polymer. Our analysis supports an acid-base reaction scheme based on an acid attacking the metal oxide precursor, generating water as byproduct of the polymeric synthesis, speeding up the reaction by solvating the PhSeH. The reaction readily goes to completion within 30 min in a supersaturated PhSeH / N2 atmosphere at 90 {\deg}C. Our analysis suggests the absence of precursor's leftovers or oxidized species that could contribute to the intra-gap states. By tuning the reaction parameters, we gained control on film morphology to obtain substrate-parallel oriented micro-crystals showing different excitonic absorption intensities. Finally, centimeters size high quality [AgSePh] NC films could be obtained, enabling exploitation of their optoelectronic properties, such as UV photodetection, in large-area applications.