Vapor Phase Infiltration Improves Thermal Stability of Organic Layers in Perovskite Solar Cells

Abstract

Despite the rapid increase in power conversion efficiency (PCE) of perovskite solar cells (PSCs) over the past decade, stability remains a major roadblock to commercialization. This work shows vapor phase infiltration (VPI) as a tool to create hybrid organic−inorganic layers that improve the stability of organic charge transport layers, such as holeselective spiro-OMeTAD in PSCs and in other organic electronic devices. Using X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and grazing incident wide-angle X-ray scattering (GIWAXS), we identify that infiltration of TiO x via VPI hinders the crystallization of the spiro-OMeTAD layer by likely preventing the π−π stacking of the molecules. Infiltrated PSCs retained more than 80% of their original efficiency after an operando stability test of 200 h at 75 °C, double the efficiency retained by devices without infiltration, in which the efficiency rapidly decreases in the first 50 h. This work provides a blueprint for using VPI to stabilize organic charge transport layers via prevention of π−π stacking leading to deleterious crystallization that shortens device lifetimes.

Dealkylation of Poly(methyl methacrylate) by TiCl4 Vapor Phase Infiltration (VPI) and the Resulting Chemical and Thermophysical Properties of the Hybrid Material

“…Vapor phase infiltration (VPI) infuses inorganic species into polymers by exposing the polymer to vapor-phase metal–organic or metal halide precursors that sorb into and become “entrapped” within the polymer. − The resultant organic–inorganic hybrid materials have properties that differ from the pure polymer. ,− For example, polymers and block copolymers infiltrated with TiO x have been shown to have altered mechanical, optical, chemical, and thermal properties. ,,− The properties of these hybrids are dependent upon the quantity of infiltrated inorganic material, the chemical bonding between the organic and inorganic components, and the spatial distribution of the inorganic component. ,,, …”

“…Although the entrapment mechanism is not fully understood, TiCl 4 infiltrated polymers have been shown to have altered chemical, thermal, optical, and electrical properties. ,,,, Additionally, PMMA/TiO 2 nanocomposites formed from TiO 2 nanoparticles have showed enhanced properties such as increased thermal stability, increased refractive index, and increased UV absorption. , Thus, these TiO x /PMMA hybrids likely have potential interest for numerous applications.…”

“… 1 − 7 The resultant organic–inorganic hybrid materials have properties that differ from the pure polymer. 5 , 7 − 17 For example, polymers and block copolymers infiltrated with TiO x have been shown to have altered mechanical, optical, chemical, and thermal properties. 5 , 7 , 16 − 18 The properties of these hybrids are dependent upon the quantity of infiltrated inorganic material, the chemical bonding between the organic and inorganic components, and the spatial distribution of the inorganic component.…”

Efficiently tuning the electrical performance of PBTTT-C14 thin film via in situ controllable multiple precursors (Al2O3:ZnO) vapor phase infiltration

“…Recently, the organic and inorganic nanocomposites, consisting of inorganic semiconductor nanocrystals and organic conjugated polymers, are potentially meritorious in solid-state batteries [1][2][3], flexible electronics [4,5], optical devices [6][7][8][9] and solar battery [10][11][12]. This combination endows the synthesized hybrid material to possess the beneficial advantages of both materials.…”

Nanographene Coupled with Interfacial Pyrene Derivatives for Thermally Stable Perovskite Solar Cells

“…Additives such as lithium bis­(trifluoro­methane­sulfonyl)­imide (LiTFSI) and tert -butyl­pyridine (tBP) are usually required to improve the conductivity of spiro-MeOTAD. However, such additives have negative effects on the thermal properties of spiro-MeOTAD by lowering T g . − The intrinsic poor conductivity in the pristine spiro-MeOTAD originates from molecular disorder and the large inter­molecular distance. , To overcome the thermal instability issue, one solution to enhance the thermal stability is to employ new additives for spiro-MeOTAD. For example, additives of poly­(9-vinyl­carbazole) and 4-( tert -butyl)­pyridinium bis­(trifluoro­methane­sulfonyl)­imide (BPTFSI) led to 80% retention of the initial PCE after 500 h at 85 °C, and 80% of the initial PCE was maintained after 796 h at 70 ± 3 °C using spiro-MeOTAD 2+ ­(TFSI) 2 and 4-( tert -butyl-1-methyl­pyridinium bis­(trifluoro­methane­sulfonyl)­imide (TBMPTFSI) .…”