3,6-Carbazole vs 2,7-carbazole: A comparative study of hole-transporting polymeric materials for inorganic–organic hybrid perovskite solar cells

Abstract

SummaryThe ever increasing demand for clean energy has encouraged researchers to intensively investigate environmentally friendly photovoltaic devices. Inorganic–organic hybrid perovskite solar cells (PSCs) are very promising due to their potentials of easy fabrication processes and high power conversion efficiencies (PCEs). Designing hole-transporting materials (HTMs) is one of the key factors in achieving the high PCEs of PSCs. We now report the synthesis of two types of carbazole-based polymers, namely 3,6-Cbz-EDOT and 2,7-Cbz-EDOT, by Stille polycondensation. Despite the same chemical composition, 3,6-Cbz-EDOT and 2,7-Cbz-EDOT displayed different optical and electrochemical properties due to the different connectivity mode of the carbazole unit. Therefore, their performances as hole-transporting polymeric materials in the PSCs were also different. The device based on 2,7-Cbz-EDOT showed better photovoltaic properties with the PCE of 4.47% than that based on 3,6-Cbz-EDOT. This could be due to its more suitable highest occupied molecular orbital (HOMO) level and higher hole mobility.

Polycarbazole and Its Derivatives: Synthesis and Applications. A Review of the Last 10 Years

“…However, since it is not a conjugated polymer its transport is carried out by radical cation hopping among the discrete carbazole units [ 77 ]. Since them, many research have been focus on the development of 3,6 disubstitued carbazoles, taking advantage of the high reactivity of 3,6 positions [ 148 ]. In this context, linear and hyperbranched 3,6-carbazole derivatives present excellent redox activity, photorefractive and nonlinear optical properties [ 106 , 149 ].…”

Dopant‐Free Hole Transporting Materials for Perovskite Solar Cells

“…Carbazole‐based polymers have tunable optical and electrochemical properties and are widely used in a variety of organic electronics, such as OLEDs, OFETs, and bulk heterojunction solar cells . Two carbazole‐based polymers, 3,6‐Cbz‐EDOT ( 27 ) and 2,7‐Cbz‐EDOT ( 28 ), were used as dopant‐free HTMs for perovskite devices by Li et al In these conjugated polymers, carbazole monomers were copolymerized with the electron‐rich 3,4‐ethylenedioxythiophene (EDOT) unit to enhance the electron donating properties of the obtained HTMs. Employing 2,7‐Cbz‐EDOT, PCE of 4.47% has been obtained for PSC devices, which was higher than the efficiency obtained for 3,6‐Cbz‐EDOT.…”

Synthesis of 1,1,4,4‐Tetracyanobuta‐1,3‐Dienes using Tetracyanoethylene Oxide via [3+2]‐Cycloaddition‐Ring Opening Reaction

“…The click‐type [2+2] CA‐RE is a robust method for the preparation of non‐planar, π‐conjugated, donor‐acceptor (D−A) chromophores that exhibit intense intramolecular charge‐transfer (CT) bands with lower energy [12] . Some of them have found applications in devices for all‐optical switching, [2a] organic field‐effect transistor, [13] light‐emitting diodes, [14] hole‐transporting materials in solar cell, [15] and has also shown remarkable third‐order nonlinear optical properties [9b] …”