2D-Self-Assembled Organic Materials in Undoped Hole Transport Bilayers for Efficient Inverted Perovskite Solar Cells

Abstract

Interfaces between photoactive perovskite layer and selective contacts play a key role in the performance of perovskite solar cells (PSCs). The properties of the interface can be modified by the introduction of molecular interlayers between the halide perovskite and the transporting layers. Herein, two novel structurally related molecules, 1,3,5-tris(α-carbolin-6-yl)benzene (TACB) and the hexamethylated derivative of truxenotris(7azaindole) (TTAI), are reported. Both molecules have the ability to self-assemble through reciprocal hydrogen bond interactions, but they have different degrees of conformational freedom. The benefits of combining these tripodal 2D-self-assembled small molecular materials with well-known hole transporting layers (HTLs), such as PEDOT:PSS and PTAA, in PSCs with inverted configuration are described. The use of these molecules, particularly the more rigid TTAI, enhanced the charge extraction efficiency and reduced the charge recombination. Consequently, an improved photovoltaic performance was achieved in comparison to the devices fabricated with the standard HTLs.

Key Roles of Interfaces in Inverted Metal-Halide Perovskite Solar Cells

“…Initially, SAMs were used in the production of organic solar cells. The chemical bond formation and enhanced hole and electron transport led to improved optical and electrical properties. ,− SAM is a popular choice for surface modification methods . However, it remains a challenge to deposit ordered dense SAM layers due to the nature of the substrate surface chemistry .…”

On-Surface Synthesis of a Radical 2D Supramolecular Organic Framework

“…In this work, we report the on-surface synthesis of a 2D hydrogen-bonded organic radical framework (2D-HBORF) on a Au(111) surface, achieved from a rationally designed tripodal starting material, 1 , that incorporates 7-azaindole building blocks to induce an extended 2D preorganization through hydrogen bond-directed self-assembly . This approach has been demonstrated to improve the stability of organic semiconductors in different devices. − We report the on-surface synthesis of an unprecedented fluoradene-based compound 3 , with an intrinsic monoradical state, which assembles forming a 2D magnetic array. The rationalization of the reaction mechanism reveals that the formation of the radical compound 3 is driven by a single gold atom on the surface (adatom), − providing suitable experimental conditions to yield the strained fluoradene system. , Here, we demonstrate the controlled and scalable formation of large defect-free 2D-HBORFs on Au(111), ordered in a Kagome-honeycomb phase, , in the size of hundreds of nanometers.…”

“… 11 This approach has been demonstrated to improve the stability of organic semiconductors in different devices. 36 − 38 We report the on-surface synthesis of an unprecedented fluoradene-based compound 3 , with an intrinsic monoradical state, which assembles forming a 2D magnetic array. The rationalization of the reaction mechanism reveals that the formation of the radical compound 3 is driven by a single gold atom on the surface (adatom), 39 − 41 providing suitable experimental conditions to yield the strained fluoradene system.…”

Organic‐inorganic hybrid material for hole transport in inverted perovskite solar cells

“…[4] High-performing PSCs rely on holetransporting materials (HTMs) to facilitate charge extraction and transport while preventing photoinduced carrier recombination. [5][6][7][8][9][10][11][12] As a crucial part of p-i-n-type PSCs, poly (3,4ethylenedioxythiophene) polystyrene sulfonate (PEDOT : PSS) and poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) have become the widely used HTMs in PSCs that exhibit high efficiencies. [13][14][15][16] However, despite their desirable properties and remarkable performance, these HTMs suffer from low hole mobility and high costs associated either with the complex synthetic routes or purification methods.…”