Synthesis and Thermal, Photophysical, Electrochemical Properties of 3,3-di[3-Arylcarbazol-9-ylmethyl]oxetane Derivatives.

Mateusz Korzec,Agnieszka Katarzyna Pająk,Paweł Gnida,Marharyta Vasylieva,Nizy Sara Samuel,Sonia Kotowicz,Ewa Schab-Balcerzak,Daiva Tavgeniene,Saulius Grigalevicius,Gintare Krucaite,Raminta Beresneviciute,Jan Grzegorz Malecki

doi:10.3390/ma14195569

Abstract

Novel oxetane-functionalized derivatives were synthesized to find the impact of carbazole substituents, such as 1-naphtyl, 9-ethylcarbazole and 4-(diphenylamino)phenyl, on their thermal, photophysical and electrochemical properties. Additionally, to obtain the optimized ground-state geometry and distribution of the frontier molecular orbital energy levels, density functional theory (DFT) calculations were used. Thermal investigations showed that the obtained compounds are highly thermally stable up to 360 °C, as molecular glasses with glass transition temperatures in the range of 142–165 °C. UV–Vis and photoluminescence studies were performed in solvents of differing in polarity, in the solid state as a thin film on glass substrate, and in powders, and were supported by DFT calculations. They emitted radiation both in solution and in film with photoluminescence quantum yield from 4% to 87%. Cyclic voltammetry measurements revealed that the materials undergo an oxidation process. Next, the synthesized molecules were tested as hole transporting materials (HTM) in perovskite solar cells with the structure FTO/b-TiO2/m-TiO2/perovskite/HTM/Au, and photovoltaic parameters were compared with the reference device without the oxetane derivatives.

Highlights

We describe synthesis and characterization of new simple carbazolebased oxetanes with 1-naphthyl, 9-ethylcarbazolyl and 4-(diphenylamino)phenyl moieties
9H-Carbazole (1), 3,3-bis(chloromethyl)oxetane, 4-(diphenylamino)phenylboronic acid, 9-ethyl-9H-carbazole-3-boronic acid pinacol ester, naphthalene-1-boronic acid, bispalladium(II) dichloride (Pd(PPh3 )2 Cl2 ), K2 CO3, KOH, KI, KIO3, tetra-n-butylammonium hydrogen sulfate (TBAHS), Na2 SO4 and solvents were purchased from Sigma Aldrich (Merck, Darmstadt, Germany) and used as received
Molecules with 9-ethylcarbazol-3-yl (5) and 4-(diphenylamino)phenyl (6) substituents were obtained as amorphous materials

Summary

Introduction

Investigations into and development of efficient and cheap solar cells is a technological area where traditional silicon-based solar cells have been successfully commercialized regardless of some disadvantages At this time, perovskite solar cells (PSCs) are regarded as one of the best alternatives to siliconbased photovoltaic (PV) devices. It should be noted that it is an expensive material due to its complicated synthesis, mediocre hole carrier mobility and negative impact on stability which significantly increase the production cost of PV devices and their stability [6] Due to these reasons the synthesis and investigation of novel efficient HTM is one of the hottest research topics in the PSCs field [7,8,9,10]. Among the reported HTM, carbazole-based compounds have drawn much attention due to good charge-transport ability of the carbazole units and low-cost of synthesis of the derivatives, which have provided a wide range of HTM by simple synthesis methods [11,12,13]

Methods

Results

Conclusion