Self-cleaning Spiro-OMeTAD via multimetal doping for perovskite photovoltaics

Record power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) are usually achieved using organic spiro-OMeTAD. However, conventional doping with hygroscopic dopants (LiTFSI and tBP) leads to compromised device stability. We introduce a synergistic mixed doping strategy that utilizes a combination of metal-TFSI dopants-LiTFSI, KTFSI, NaTFSI, Ca(TFSI)₂, and Mg(TFSI)₂-to enhance doping efficiency while effectively removing hygroscopic contaminants from the Spiro-OMeTAD solution. This approach achieves PCEs exceeding 25% and significantly improves stability under harsh environmental conditions. Notably, Ca(TFSI)₂ and Mg(TFSI)₂ facilitate enhanced oxidative doping, while NaTFSI promotes interstitial doping in the bulk perovskite. Additionally, KTFSI serves as a catalytic agent, lowering the reaction energy barrier for the other dopants, thereby accelerating spiro-OMeTAD ion radical production. These findings underscore the potential of synergistic doping in optimizing the performance and longevity of photovoltaic devices.