The effect of rubidium and guanidinium additives on the morphological, optoelectronic and photovoltaic properties of the state-of-the-art triple A-cation based PSCs is investigated.
Interfacial engineering between the perovskite and hole transport layers has emerged as an effective way to improve perovskite solar cell (PSC) performance. A variety of organic halide salts are developed to passivate the traps and enhance the charge carrier transport. Here, the use of guanidinium iodide (GuaI) for interfacial modification of mixed‐cation (Cs)x(FA)1−xPbI3 perovskite films, which results in the formation of a low‐dimensional δ‐FAPbI3‐like phase on the 3D perovskite surface, is reported. The presence of this thin layer facilitates charge transfer at interfaces and reduces charge carrier recombination pathways as evidenced by enhanced carrier lifetimes and favorable interfacial band alignment. As a result, the power conversion efficiency of the control device is boosted from 19.22% to 20.07%, mainly due to improved open‐circuit voltage (Voc) and fill factor. Furthermore, the post‐treatment with GuaI improves the moisture stability of perovskite polycrystalline films and ambient stability of PSCs.
The quality of perovskite films plays a crucial role in improving the optoelectronic properties and performance of perovskite solar cells (PSCs). Herein, high‐quality CsxFA1−xPbI3 perovskite films with different compositions (x = 0, 5, 10, and 15) are achieved by controlling the amount of cesium chloride (CsCl) in the respective FAPbI3 precursor solution. The effects of CsCl addition on the morphological and optoelectronic properties of the resulting perovskite films and on the performance of the corresponding devices are systematically studied. Introduction of CsCl into FAPbI3 shows a great potential to stabilize the α‐FAPbI3 perovskite phase by forming CsxFA1−xPbI3 films with improved morphology and carrier lifetimes. With an optimal 10 mol% CsCl additive, the average power conversion efficiency (PCE) is increased from 16.83 ± 0.30% for the reference FAPbI3‐based PSCs to 18.87 ± 0.25% (with a steady‐state PCE of 18.89%). Moreover, the optimized device performance is more stable after 20 days than the controlled one under ≈40% humidity in air.
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