Achieving efficient and stable carbon-based perovskite solar cells by grain size doubling and perfect connection of perovskite using borate ionic liquid

Commercially available carbon was used instead of the noble metals. • The grain size of the perovskite was doubly increased and grain boundaries were reduced by [C 6 Py]BF 4 modification. • [C 6 Py]BF 4 modification reduces the non-radiative recombination and enhances the charge transport. • The carbon-based device modified with 0.3 vol% [C 6 Py]BF 4 achieved an optimized efficiency of 15.42%. Additive engineering is one of the key strategies for enhancing the performance of perovskite solar cells. The ionic liquid 1-hexylpyridinium tetrafluoroborate ([C 6 Py]BF 4 ) was employed as an additive in the perovskite precursor solution. [C 6 Py]BF 4 can regulate the crystallization process of the perovskite. Meanwhile, N in the pyridinium group, possessing a lone electron pair, acts as a hydrogen bond acceptor, forming N-H···I hydrogen bonds with the I − in the perovskite. The formation of hydrogen bonds stabilizes the position of I − , suppressing its migration. Additionally, the BF 4 − passivates defects by coordinating with undercoordinated Pb 2+ . SEM characterization revealed that the perovskite films modified with [C 6 Py]BF 4 exhibited a doubling of grain size and a reduction in grain boundaries, resulting in a significant decrease in the defect density within the devices. Consequently, non-radiative recombination was suppressed, ion migration was mitigated, and charge carrier lifetime was improved. At the optimal concentration of 0.3 vol%, the power conversion efficiency of the device reached 15.42%, representing an 8.5% enhancement compared to the pristine device. Furthermore, the hysteresis effect was significantly reduced, and the long-term stability of the device was improved. The ionic liquid 1-hexylpyridinium tetrafluoroborate ([C 6 Py]BF 4 ) was employed as an additive in the perovskite precursor solution. After modification with [C 6 Py]BF 4 , the grain size of the perovskite film was significantly doubly increased, while grain boundaries were reduced, leading to a substantial decrease in defect density within the device. Consequently, non-radiative recombination was suppressed, ion migration was mitigated, and charge carrier lifetime was improved. At the optimal concentration of 0.3 vol%, the power conversion efficiency (PCE) of the device reached 15.42%, representing an 8.5% enhancement compared to the pristine device. Furthermore, the hysteresis effect was significantly reduced, and the long-term stability of the device was improved. Download: Download high-res image (148KB) Download: Download full-size image