Interface engineering is of paramount importance for optimizing carrier dynamics and stability of perovskite solar cells (PSCs), but little attention has been paid to understanding and managing the buried interfaces. Here, a molecular bridge strategy is developed to modify the properties of buried interfaces in n-i-p PSCs by introducing a multi-functional additive 2-Hydroxyethyl trimethylammonium chloride (ChCl) in the bottom SnO 2 electron transport layer. The ChCl treatment enables bifacial defects passivation and improved perovskite quality, leading to notably enhanced electron extraction and suppressed non-radiative recombination at the buried interfaces. As a result, a significantly improved power conversion efficiency (PCE) from 20.0% to 23.07% with a remarkable open-circuit voltage (V oc ) of up to 1.193 V is achieved, along with superior stability (up to 4000 h) for the unsealed devices under different conditions (moisture, heat and maximum power point). Furthermore, this molecular bridge strategy demonstrates the ability to release the stress in perovskite thin film and simultaneously strengthen the interfacial toughness in flexible PSCs, yielding remarkable mechanical stability and a champion PCE of 21.50%. This study offers deep insights into understanding and engineering the buried interfaces and provides effective strategies to further enhance the performance and stability of PSCs.
The perovskite buried interfaces have demonstrated pivotal roles in determining both the efficiency and stability of perovskite solar cells (PSCs); however, challenges remain in understanding and managing the interfaces due to their non‐exposed feature. Here, we proposed a versatile strategy of pre‐grafted halides to strengthen the SnO2–perovskite buried interface by precisely manipulating perovskite defects and carrier dynamics through alteration of halide electronegativity (χ), thereby resulting in both favorable perovskite crystallization and minimized interfacial carrier losses. Specifically, the implementation of fluoride with the highest χ induces the strongest binding affinity to uncoordinated SnO2 defects and perovskite cations, leading to retarded perovskite crystallization and high‐quality perovskite films with reduced residual stress. These improved properties enable champion efficiencies of 24.2% (the control: 20.5%) and 22.1% (the control: 18.7%) in rigid and flexible devices with extremely low voltage deficit down to 386 mV, all of which are among the highest reported values for PSCs with a similar device architecture. In addition, the resulting devices exhibit marked improvements in the device longevity under various stressors of humidity (>5000 h), light (1000 h), heat (180 h), and bending test (10 000 times). This method provides an effective way to improve the quality of buried interfaces toward high‐performance PSCs.
Surface plasmon resonance (SPR) bridges photonics and photoelectrochemistry by providing an effective interaction between absorption and confinement of light to surface electrons of plasmonic metal nanostructures (PMNs). SPR enhances the Raman intensity enormously in surface-enhanced Raman spectroscopy (SERS) and leads to the plasmon-mediated chemical reaction on the surface of nanostructured metal electrodes. To observe variations in chemical reactivity and selectivity, we studied the SPR photoelectrochemical reactions of para-aminobenzoic acid (PABA) on nanostructured gold electrodes. The head-to-tail coupling product “4-[(4-imino-2,5-cyclohexadien-1-ylidene)amino]benzoic acid (ICBA)” and the head-to-head coupling product p,p′–azodibenzoate (ADBA) were obtained from PABA adsorbed on PMN-modified gold electrodes. In particular, under acidic and neutral conditions, ICBA was obtained as the main product, and ADBA was obtained as the minor product. At the same time, under basic conditions, ADBA was obtained as the major product, and ICBA was obtained as the minor product. We have also provided sufficient evidence for the oxidation of the tail-to-tail coupling reaction product that occurred in a nonaqueous medium rather than in an aqueous medium. The above finding was validated by the cyclic voltammetry, SERS, and theoretical calculation results of possible reaction intermediates, namely, 4-aminophenlylenediamine, 4-hydroxyphenlylenediamine, and benzidine. The theoretical adsorption model and experimental results indicated that PABA has been adsorbed as para-aminobenzoate on the gold cluster in a bidentate configuration. This work offers a new view toward the modulation of selective surface catalytic coupling reactions on PMN, which benefits the hot carrier transfer efficiency at photoelectrochemical interfaces.
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