Nonaromatic Green‐Solvent‐Processable, Dopant‐Free, and Lead‐Capturable Hole Transport Polymers in Perovskite Solar Cells with High Efficiency

Abstract

With the recent developments in the efficiency of perovskite solar cells (PSCs), diverse functionalities are necessary for next‐generation charge‐transport layers. Specifically, the hole‐transport layer (HTL) in the various synthesized materials modified with functional groups is explored. A novel donor–acceptor type polymer, alkoxy‐PTEG, composed of benzo[1,2‐b:4,5:b′]dithiophene and tetraethylene glycol (TEG)‐substituted 2,1,3‐benzothiadiazole is reported. The alkoxy‐PTEG exhibits high solubility even in nonaromatic solvents, such as 3‐methylcyclohexanone (3‐MC), and can prevent possible lead leakage via chelation. The optical and electronic properties of alkoxy‐PTEG are thoroughly analyzed. Finally, a dopant‐free alkoxy‐PTEG device processed with 3‐MC exhibits 19.9% efficiency and a device with 2‐methyl anisole, which is a reported aromatic food additive, exhibits 21.2% efficiency in a tin oxide planar structure. The PSC device shows 88% stability after 30 d at ambient conditions (40–50% relative humidity and room temperature). In addition, nuclear magnetic resonance reveals that TEG groups can chelate lead ions with moderate strength (Kbinding = 2.76), and this strength is considered to be nondestructive to the perovskite lattice to prevent lead leakage. This is the first report to consider lead leakage and provide solutions to reduce this problem.

High‐Performance Planar Heterojunction Perovskite Solar Cells Based on BaCl2 Additive and Power Conversion Efficiency of Over 21%

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junction devices. [4][5][6][7][8][9][10] Compared to traditional solar cells, PSCs have high stability, high efficiency, low cost, and simple structure. PSCs have two iconic structures: mesoporous and planar structures.

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“…PSCs have two iconic structures: mesoporous and planar structures. [9,11] The planar structure has been widely used because it has high PCE and simple preparation process; new attempts and changes have been made continuously to optimize its performance. [12][13][14][15][16] Improving the performance of planar PSCs is critically dependent on the properties of both their perovskite active layers and interfaces.…”

Green–Solvent–Processable Perovskite Solar Cells

“…Reproduced with permission. [ 20 ] Copyright 2020, WILEY‐VCH Verlag GmbH & Co. KgaA. d) The PL spectrum of glass/CB‐perovskite, glass/EA‐perovskite, glass/CB‐perovskite/Spiro‐OMeTAD, glass/EA‐perovskite/Spiro‐OMeTAD.…”

“…2,2′,7,7′‐tetrakis( N,N ‐di‐pmethoxyphenylamine)‐9,9′‐spirobifluorene (Spiro‐OMeTAD) is the most commonly used HTM in PSCs, but it can be dissolved only in halogenous or toxic solvent such CB, dichlorobenzene (DCB), and toluene. [ 20 ] The calculated Hansen solubility in Figure 3b indicated that uniting alkoxy side chains and tetraethylene glycol side chains is suitable for green preparation process due to superior solubility capacity ( R 0 ). Furthermore, the alkoxy chains have strong interaction with Pb 2+ with the binding constant of 2.76 m −1 (Figure 3c), which indicated excellent ability of coordination with Pb 2+ .…”

N-Substituted Phenothiazines as Environmentally Friendly Hole-Transporting Materials for Low-Cost and Highly Stable Halide Perovskite Solar Cells

“…There are very few reports regarding HTMs processed in nonhalogenated solvents. 24 − 28 Nevertheless, in all the reported examples, the HTMs were mostly synthesized in modest overall yields via onerous multistep syntheses employing costly and toxic palladium catalysts and were purified via stringent and long procedures that limit their scalability. 24 − 28 Thus, HTMs that combine green solvents processability with cost-effective and eco-friendly synthesis and purification are still lacking.…”