Synergistic versatile bistriflimide salts in light-accelerated spiro-OMeTAD oxidation and perovskite module photovoltaics engineering

2,2',7,7-tetrakis(N,N-di(4-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD) remains as the most widely used material for the hole transport layer (HTL) in efficient n-i-p perovskite photovoltaic devices. However, the conventional recipe, i.e., spiro-OMeTAD doped with bis(trifluoromethane)sulfonimide (LiTFSI) and 4-tert-butylpyridine (tBP) leads to poor device operational stability. Here, we introduce a strategy that employs light to generate protons in the precursor solution by ammonium TFSI dopants, which in turn increases the conductivity of HTL by the formation of oxidized spiro (referred to as light-oxidation doping treatment or LODT in short). Devices utilizing the LODT strategy results in reduced hysteresis and enhanced operational stability. The best perovskite solar module (PSM) achieves a certified power conversion efficiency (PCE) of 20.95% for a 12.83 cm² aperture area, standing out as one of the best Li-free spiro-OMeTAD HTL based PSMs. Furthermore, the unencapsulated perovskite solar cell has an extended operational stability profile exceeding 700 hours with only 7% decrease in the initial PCE.