Study on the Properties of Organic–Inorganic Hole Transport Materials in Perovskite Based on First-Principles

Abstract

Newport Inc. was licensed recently by the National Renewable Energy Laboratory of the United States to update the highest efficiency of the perovskite solar cell (PSC) certification of PSCs by 23.7%. Exploring new hole transfer layer is the key to the future development of PSC. In this paper, we constructed seven organic hole transport material molecules such as copper-phthalocyanine (CuPc), 2',7'-bis(bis(4-methoxyphenyl)amino)spiro[cyclopenta-[2,1-b:3,4-b']dithiophene-4,9'-fluorene] (FDT), Poly-triarylamine (PTAA), poly(3,4-ethylenedioxy thiophene)/poly(styrenesulfonate) (PEDOT/PSS) poly(3-hexylthiophene) (P3HT) and six in-organic hole transport material molecules such as CuCSN, CuI, InCuS2, CuO, Cu2O, NiO with Material Studio software. By the structure optimization, their energy band, density of state (DOS), HOMO/lowest unoccupied orbit (LUMO) energy level and absorption spectrum were calculated. Furthermore, the HOMO/LUMO electron cloud distribution map of FDT molecule was analyzed in detail. The results show that the electron cloud is closer to the nucleus with the increase of the isopotential surface value. From the absorption spectra, the absorption wavelengths of most inorganic hole transport materials are mainly concentrated at about 200 nm, which is relatively short. But the absorption wavelengths of organic hole transport materials are distributed in long wavelength region, most of them are above 2000 nm. Only the absorption spectra of PTAA, Spiro OMetad and CuPc are in the range of solar spectrum. The HOMO energy levels of seven organic hole transport materials are slightly higher than the values of valence band of CH3NH3PbI3 and NH2CH = NH2PbI3, which are favorable for carrier injection and transport. The band gap of inorganic hole transport materials CuCSN and CuI is wider. From the energy band structure curve, the effective mass of NiO, CuO, Cu2O carriers is smaller, which the carrier transport rate is relatively high. The hole transport material must have high hole mobility and hole conductivity so as to ensure the effective transport of the hole at the interface between the hole transport layer and the perovskite layer.