Low-Cost Dopant Additive-Free Hole-Transporting Material for a Robust Perovskite Solar Cell with Efficiency Exceeding 21%

Abstract

Developing hole-transporting materials (HTMs) with appropriate molecular configuration and charge mobility is important to improve perovskite solar cell (PSC) photovoltaic performance and their feasibility for commercialization. In this work, a novel pyramidal-shaped low-cost HTM coded MeOTTVT is prepared through extension of π-conjugation based on a triphenylamine core. Carbon–carbon double bonds are introduced between the core and p-methoxyl triphenylamine to improve the planarity of the HTM, favoring intermolecular stacking of MeOTTVT and thus improving the hole mobility of the corresponding hole-transporting layer (HTL). The p-methoxyl triphenylamine-endowed HTM benefits from a highest occupied molecular orbital level well-aligned with the perovskite active layer, facilitating effective hole extraction. The champion PSC using an MeOTTVT-based dopant additive-free HTL yielded a power conversion efficiency (PCE) up to 21.30%, which is considered one of the best-performing PSCs employing a dopant additive-free small molecule HTM. In addition, the MeOTTVT-based dopant additive-free HTL exhibits outstanding thermal stability and high glass-transition temperature (T g = 137.1 °C), combined with a more hydrophobic surface; PSCs based on an MeOTTVT dopant additive-free HTL exhibit outstanding stability against moisture, 1 sun illumination, and thermal stress.

Synergistic Effect of Fluorinated Passivator and Hole Transport Dopant Enables Stable Perovskite Solar Cells with an Efficiency Near 24%

“…Since the perovskite is protected by the TiO 2 or SnO 2 ETL as well the transparent conductive substrate, e.g. a fluorine-doped tin oxide (FTO) or indium-doped tin oxide (ITO) glass, water and oxygen ingression from the environment destroys the PSCs mainly via the perovskite/HTL interface. , Ambient moisture uptake due to the intrinsic hydrophilicity of the perovskite active layer materials is one of the key issues resulting in poor operational stability of the PSCs. , In addition, the widely used HTL additives, such as lithium bis­(trifluoromethanesulfonyl)­imide (Li-TFSI) and tert -butylpyridine ( t BP), are hydrophilic, intensifying moisture penetration from ambient air to the perovskite through the HTL. − Work has been done to address these problems, by employing a 2D/3D structure and using surface passivation to protect the perovskite, by focusing on the development of moisture repelling HTMs , or by developing new additives . However, simultaneously increasing the hydrophobicity of the perovskite and the HTL is of great importance to attain long-term stability of highly efficient PSCs.…”

“…16,17 In addition, the widely u s e d H T L a d d i t i v e s , s u c h a s l i t h i u m b i s -(trifluoromethanesulfonyl)imide (Li-TFSI) and tert-butylpyridine (tBP), are hydrophilic, intensifying moisture penetration from ambient air to the perovskite through the HTL. 18−20 Work has been done to address these problems, by employing a 2D/3D structure 21 and using surface passivation 22 to protect the perovskite, by focusing on the development of moisture repelling HTMs 23,24 or by developing new additives. 25 However, simultaneously increasing the hydrophobicity of the perovskite and the HTL is of great importance to attain long-term stability of highly efficient PSCs.…”

A dopant-free hole transport material boosting the performance of inverted methylamine-free perovskite solar cells

“…As for PTAA, the negative charge distribution is relatively uniform. With regard to PFDTS, the negative charge is mainly concentrated on the oxygen atom in the carbonyl group and the entire plane of DTP, which can act as Lewis base anchors to interact with Pb, 34 while the positive charge is mainly concentrated on the hydroxyl group and the entire plane of fluorene. This differential distribution of positive and negative charges is conducive to the π–π* transition of the charge.…”

Simple Yet Efficient: Arylamine‐Terminated Carbazole Donors for Organic Hole Transporting Materials

“…Hole transport materials (HTMs) are necessary for PSCs to extract and transport the free photogenerated holes within the perovskite material. Efforts have been devoted to designing and fabricating HTMs from organic building blocks, [ 5,6 ] including organic small molecules, [ 7–36 ] polymers, [ 37,38 ] and organometallic compounds. [ 39–41 ] Among them small organic HTMs have received tremendous attentions due to their high performance, structural variety, and easy fabrication.…”