Efficient Perovskite Solar Cells Based on Dopant‐Free Spiro‐OMeTAD Processed With Halogen‐Free Green Solvent

In this paper, highly efficient (17%) perovskite solar cells (PSCs) based on a hole‐transporting layer (HTL) made of dopant‐free Spiro‐OMeTAD processed from a non‐halogenated solvent (THF) are reported for the first time. In addition to the high efficiency, a negligible hysteresis effect is observed for the devices with dopant‐free Spiro‐OMeTAD hole‐transporting material (HTM), which is often a problem for planar n‐i‐p type PSCs. By eliminating the hydroscopic dopants, the ambient stability of the completed PSC devices are much improved. Another advantage of using THF as a solvent is that much less of the Spiro‐OMeTAD material is required (5 mg ml⁻¹) to coat the HTL compared to that used in a conventional chlorobenzene solvent (70 mg ml⁻¹). Our result provides a simple yet effective method to fabricate dopant‐free PSCs toward cost‐effective and environmental friendly production of PSCs with enhanced stability.