Effect of Organic Chloride Additives on the Photovoltaic Performance of MA‐Free Cs_0.1FA_0.9PbI₃ Perovskite Solar Cells

Abstract

The use of chloride additives to achieve high performance in perovskite solar cells (PSCs) is extensively reported in perovskite research. However, few studies are dedicated to understanding and comparing the underlying effects of ammonium cations in organic chloride additives. Herein, the effect of ACl additives (A: ethylammonium [EA], propylammonium [PA], butylammonium [BA]), with increasing ammonium size, on the performance of MA‐free Cs0.1FA0.9PbI3 PSCs is investigated. The obtained results indicate that Cl promotes the growth of large grains, while organic cations facilitate grain favorable orientation. Moreover, it is observed that EACl evaporates during thermal annealing despite the similar ionic size of EA to that of FA, which would lead to A‐site incorporation. However, PACl and BACl remain in final films, passivating grain boundaries. Moreover, by using double BACl–EACl additive, the films show considerably increased grain dimensions, passivated grain boundaries, and longer carrier lifetime. As a result, planar PSCs based on engineered Cs0.1FA0.9PbI3 layers achieve higher power conversion efficiency of 20.98%, 20.07%, 19.64%, and 19.03% for BACl–EACl, BACl, PACl, and EACl, respectively, compared to 17.58%‐efficiency for control PSCs. Moreover, this additive‐based approach also increases moisture resistance of the Cs0.1FA0.9PbI3 films, which consequently enhances the device ambient stability.

Recent advances in ionic molecules applied in perovskite solar cells

“…However, there was only a few reports on this issue in the past year, which is probably due to the complexity in the Fig. 10 Chemical structures of DAGCl, 82 3AP, 83 trometamol, 84 BHF, 85 BACl, 86 BHC, OAm, 87 CsSt 88 and TDCA. 89 molecular design and synthesis.…”

“…84 All these groups could form coordinate bonds with Pb 2+ and hydrogen bonds with I − , which was also demonstrated by the other precursor additive BHF applied in Zhu's work. 85 Other amino-based precursor additives such as butylammonium chloride (BACl), 86 BHC and OAm 87 exhibited similar functions. It should be noted that Castriotta et al developed a universal multi-additive strategy for defect passivation, with the combination of three precursor additives including BHC, OAm and the IL BMIMBF 4 .…”

Ruddlesden–Popper Perovskite Nanocrystals as Interface Modification Layer for Efficient Perovskite Solar Cells

“…13−15 These defects, mainly organic cation and halide anion vacancies, usually accumulate at grain boundaries or on the surface of solution processed perovskites, which act as the nonradiative recombination centers 16,17 leading to PCE loss and instability of corresponding devices. 18,19 Therefore, researchers have developed different strategies to address the issue, such as modulation of grain size and orientation, 20,21 and passivation of bulk and/or surface defects by cations, anions or lowdimensional perovskites. 22−29 Among the strategies for surface defect passivation in perovskite, perovskite nanocrystals (P-NCs) stand out for their flexibility of composition, size, shape, and surface ligands.…”

“…The unique properties of organic–inorganic hybrid halide perovskite materials, such as their high light absorption coefficient, carrier mobility, structural tunability, and defect tolerance, , contribute to the high power conversion efficiency (PCE) of perovskite solar cells (PSCs). − However, hybrid perovskites usually suffer from intrinsic and environmental instability, − and the presence of defects further accelerates their degradation and phase transition. − These defects, mainly organic cation and halide anion vacancies, usually accumulate at grain boundaries or on the surface of solution processed perovskites, which act as the nonradiative recombination centers , leading to PCE loss and instability of corresponding devices. , Therefore, researchers have developed different strategies to address the issue, such as modulation of grain size and orientation, , and passivation of bulk and/or surface defects by cations, anions or low-dimensional perovskites. − …”