All green solvent engineering of organic-inorganic hybrid perovskite layer for high-performance solar cells

Solvent engineering technology is an important approach for fabrication of high quality perovskite films, and thereby high-performance perovskite solar cells (PSCs). However, it is strongly dependent on the usage of toxic solvents, including the host solvent and anti-solvent to prepare perovskite solutions and control the crystallization of perovskite films, respectively. The usage of toxic solvents poses a serious threat to the health of manufactures and the safety of environment. Therefore, the solvent toxicity has become a burning issue before the forthcoming commercialization of PSCs. Here, we report an all green solvent engineering to prepare high quality (FAPbI3)1-x(MAPbBr3)x (x = 0, 0.05) films, where a green Lewis base solvent of triethyl phosphate (TEP) is used to prepare (FAPbI3)1-x(MAPbBr3)x/TEP solution, and a non-polar solvent of dibutyl ether (DEE) is used as anti-solvent. In this approach, a new intermediate phase film is formed after spin-coating the (FAPbI3)1-x(-MAPbBr3)x/TEP solution on substrates, followed by dropping of DEE during spinning, and subsequently convert into perovskite films by annealing. Finally, it enables a PCE of 18.65% (x = 0) and 20.13% (x = 0.05) basing on a typical device configuration of FTO/SnO2/Perovskite/Spiro-OMeTAD/Au, which is the highest value for the all green solvent processed PSCs. More importantly, the all green solvent engineering approach can also be used to prepare another typical perovskite of MAPbI3 films for efficient solar cells. Therefore, this work not only provides an universial approach to prepare typical organic-inorganic hybrid perovskite films, but also addresses the solvent toxicity during the production of perovskite films. The green solvent engineering may pave the way for future industrial scale production of PSCs under environment friendly conditions.