Damp-heat stable and efficient perovskite solar cells and mini-modules with tBP-free hole-transporting layer

Abstract

In spiro-OMeTAD-based hole-transporting layer (HTL) protocols, 4-tert-butylpyridine (tBP) constitutes an indispensable component; however, its inclusion engenders substantial detrimental ramifications, precluding realizing thermal stability. Here, a tBP-free spiro-OMeTAD approach was successfully devised by substituting ethylene carbonate (EC) electrolyte for tBP. The electronegative carbonyl functionality forms a solvation complex with Li+ ions, addressing the solubility concern of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in chlorobenzene even without tBP. The liberated TFSI− ions facilitate the stabilization of a larger population of spiro-OMeTAD∙+ radicals, thereby enabling efficient p-doping. The EC-incorporated HTL achieved a maximum power conversion efficiency (PCE) of 25.56% (certified 25.51%). In scaled-up applications, perovskite solar mini-modules with an aperture area of 100 cm2 demonstrated a PCE of 22.14%. The elevated glass transition temperature and robustly sequestered Li+ ions endow the devices with resilience against damp-heat conditions (85 ℃/85% RH) for 1,000 hours. Our findings signify a crucial leap forward commercialization by addressing thermal stability issues.