Abstract
The long-term stability of perovskite solar cells (PSCs) remains an issue impeding their commercialization. Generally, polycrystalline perovskite thin films have many defects on the grain boundaries, which affect the optoelectronic performance and stability of the devices under moisture, heat, illumination, and the presence of an electric field condition. The O-donor Lewis base is often employed to regulate the performance of PSCs such as carbonyl and carboxyl compounds. Herein, we have developed a concept of radical molecular modulation using the O-donor group for high-performance perovskite photovoltaic devices. The judiciously designed radical modulators 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), which located at the perovskite grain boundary through interaction with the perovskite surface sites, effectively passivated the surface defects while templating the formation of large grain crystal and high-quality perovskite thin films. Accordingly, the optimized TEMPO-modulated PSCs achieved a power conversion efficiency of 20.73% with superior stability. This work makes an important contribution for exploring the effect of radical in perovskites to improve the performance of PSCs and other optoelectronic devices.
Highlights
Organic–inorganic metal halide perovskite material has attracted tremendous attention as a promising renewable energy photovoltaic material due to its excellent properties of high absorption coefficient, tunable direct band gap, low exciton binding energy, long charge carrier lifetime, and low recombination rates (Etgar et al, 2012; Kojima et al, 2012; Lee et al, 2012; Stranks et al, 2013; Xing et al, 2013; Yin et al, 2014; Dong et al, 2015)
Our results show that the addition of a small amount of free radicals can effectively improve the performance of perovskite solar cells (PSCs), which provides a new strategy for the regulation of perovskite
We explored the effects of radical small molecules with different functional groups on the optoelectronic properties of PSCs
Summary
Organic–inorganic metal halide perovskite material has attracted tremendous attention as a promising renewable energy photovoltaic material due to its excellent properties of high absorption coefficient, tunable direct band gap, low exciton binding energy, long charge carrier lifetime, and low recombination rates (Etgar et al, 2012; Kojima et al, 2012; Lee et al, 2012; Stranks et al, 2013; Xing et al, 2013; Yin et al, 2014; Dong et al, 2015). Them, Lewis bases can bind to the positively charged undercoordinated Pb2+ ions, passivating the undercoordinated defect such as pyridine (N-donor), thiophene (S-donor), and carboxyl (O-donor) derivatives (Noel et al, 2014; Lee et al, 2017; Liu et al, 2018; Yang et al, 2018; Zhang et al, 2018). In principle, these molecules have lone pair electrons on their HOMO, while lead ions have “empty orbitals” that accept lone pair electrons forming a Lewis adduct through the coordinate covalent bonds.
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