Efficient Blade-Coated p-i-n Perovskite Solar Cells and Modules Enabled by Effective Molecular N Doping.

ABSTRACT

N doping is an essential strategy to prolong electron diffusion length and improve the photovoltaic performance of p-i-n structured perovskite solar devices, but current n-dopants generally suffer from air instability, poor compatibility with perovskites, and the compensation from perovskite intrinsic defects, thus limiting their doping effectiveness. To address these issues, in this work, a new perovskite n-doping strategy is developed by incorporating an air-stable n-dopant (1-ethyl-3-methylimidazolium-2-carboxylate, EMIC) that has no detrimental effects on perovskite crystallinity and morphology. EMIC is soluble in most polar solvents and can be readily introduced into perovskite precursor solutions. Upon thermal annealing of perovskite films, the decarboxylation of EMIC releases imidazolylidene, a reactive species that highly tends to donate electrons and thus efficiently prolongs the electron diffusion length from 0.57 µm to over 1.21 µm. As a result, the blade-coated perovskite solar cells and modules realize high power conversion efficiencies of 24.3% and 20.6% at 7.4 mm2 and 25.0 cm2 aperture areas, respectively.