Control of Molecular Orientation of Spiro-OMeTAD on Substrates

Abstract

2,2′,7,7′-Tetrakis(N,N-di-p-methoxyphenylamino)-9,9′-spirobifluorene (spiro-OMeTAD) is utilized as a p-type semiconductor layer in perovskite solar cells and solid-state dye-sensitized solar cells. Spiro-OMeTAD has been known to have a spiro center, leading to a random orientation. Although the molecular orientation of organic semiconductor materials influences the conductivity, which is directly related to semiconductor device characteristics, the molecular orientation of spiro-OMeTAD has not been fully discussed. In this study, we prepared spiro-OMeTAD layers on various substrates and investigated their orientation by grazing-incidence wide-angle X-ray scattering (GIWAXS) and near-edge X-ray absorption fine structure (NEXAFS). Additionally, we demonstrated that the molecular orientation of spiro-OMeTAD could be controlled by changing their surface energies by changing the substrate materials. Consequently, we could improve the electrical conductivity by improving its molecular orientation. The results of this study provide a guideline for the preparation of organic semiconductor material layers using the wet-coating method.

Dopant‐Free Polymer HTM‐Based CsPbI2Br Solar Cells with Efficiency Over 17% in Sunlight and 34% in Indoor Light

“…The distance of π-π stacking structure and the lamellar structure was calculated to be 3.70 and 22.5 Å, respectively. These results indicate that PDTDT has a predominant face-on orientation, [14] which is favorable for hole transport in PSCs. Using the space-charge limited current (SCLC) method (Figure S1c, Supporting Information), the hole mobility of PDTDT was calculated to be 3.14 × 10 −3 cm 2 V −1 s −1 , which is higher than P3HT (1.67 × 10 −3 cm 2 V −1 s −1 ), as well as poly(DTSTPD-r-BThTPD) (1.50 × 10 −3 cm 2 V −1 s −1 ).…”

Ion-modulated radical doping of spiro-OMeTAD for more efficient and stable perovskite solar cells

“…S25 and S26). A straightforward possibility for inducing the WF change is the introduction of a macroscopic dipole, which could be induced either by a particular spiro-OMeTAD orientation ( 45 ) or by an interfacial TBMP + TFSI – accumulation ( 46 ). We excluded the former on the basis of the grazing-incidence wide-angle x-ray scattering (GIWAXS) results (fig.…”

Investigating the Molecular Orientation and Thermal Stability of Spiro‐OMeTAD and its Dopants by Near Edge X‐Ray Absorption Fine Structure

“…These findings are interesting when compared to the data reported by Shibayama et al who observed some orientation of Spiro‐OMeTAD layers when deposited on certain substrates (i.e., Si, FTO, nickel oxide, and perovskite layers). [ 43 ] They demonstrated there is variation in Spiro‐OMeTAD behavior from substrate to substrate and they suggested that Spiro‐OMeTAD orientation was influenced by substrate surface energy. However, their study did not investigate Spiro‐OMeTAD deposited on TiO 2 and so the authors believe the data reported here are the first reported on this substrate.…”