Enhanced Stability of Perovskite Solar Cells Incorporating Dopant‐Free Crystalline Spiro‐OMeTAD Layers by Vacuum Sublimation

Abstract

The main handicap still hindering the eventual exploitation of organometal halide perovskite‐based solar cells is their poor stability under prolonged illumination, ambient conditions, and increased temperatures. This article shows for the first time the vacuum processing of the most widely used solid‐state hole conductor (SSHC), i.e., the Spiro‐OMeTAD [2,2′,7,7′‐tetrakis (N,N‐di‐p‐methoxyphenyl‐amine) 9,9′‐spirobifluorene], and how its dopant‐free crystalline formation unprecedently improves perovskite solar cell (PSC) stability under continuous illumination by about two orders of magnitude with respect to the solution‐processed reference and after annealing in air up to 200 °C. It is demonstrated that the control over the temperature of the samples during the vacuum deposition enhances the crystallinity of the SSHC, obtaining a preferential orientation along the π–π stacking direction. These results may represent a milestone toward the full vacuum processing of hybrid organic halide PSCs as well as light‐emitting diodes, with promising impacts on the development of durable devices. The microstructure, purity, and crystallinity of the vacuum sublimated Spiro‐OMeTAD layers are fully elucidated by applying an unparalleled set of complementary characterization techniques, including scanning electron microscopy, X‐ray diffraction, grazing‐incidence small‐angle X‐ray scattering and grazing‐incidence wide‐angle X‐ray scattering, X‐ray photoelectron spectroscopy, and Rutherford backscattering spectroscopy.

Hexaarylbenzene based high-performance p-channel molecules for electronic applications

“…Especially, the classic 2,2′,7,7′-tetrakis-( N , N -bis(4-methoxyphenyl)amino)-9,9′-spirobifluorene (spiro-OMeTAD) molecule has been widely investigated as an HTM containing four arms of dimethoxydiphenylamine. 146 Apparently, the charge transport, hole mobility, thermal, photophysical, and electrochemical properties rely on the center core and branching segments. The HAB-based molecules were successfully utilized as HTM layers, owing to their good hole-transporting behavior and act as alternatives for the classic spiro-OMeTAD compound.…”

Toward Commercialization of Efficient and Stable Perovskite Solar Modules

“…Barranco et al used vacuum sublimation to deposit spiro‐OMeTAD films with a pressure of 10 −6 Torr to obtain a flat, dense, and compact microstructure. [ 89 ] They showed that the crystallization of the vacuum sublimation‐deposited spiro‐OMeTAD layer can be controlled by adjusting the temperature during the deposition process, which significantly improved the stability of PSCs. Although this method improves stability, the efficiency is well below that obtained with traditional spin coating methods.…”

Research facilities and highlights at the Centro Nacional de Aceleradores (CNA)

“…Multipurpose IBA chamber This chamber is equipped with a set of particle, gamma and X-Ray detectors and a large target holder to carry out simultaneously different IBA experiments (RBS, PIXE, NRA and PIGE). In this chamber, we have recently investigated the use of novel solid 4 He targets for experimental studies on nuclear reactions [3,4], the composition of solid-state hole conductor in solar cells prepared by vacuum processing [5] and a novel ionizing particle detector based on thin films multilayers [6,7]. 4.…”