Polymer Additives for Morphology Control in High‐Performance Lead‐Reduced Perovskite Solar Cells

Abstract

The organic–inorganic halide perovskite solar cells (PSCs) are rapidly developed in just a few years due to its high power conversion efficiency. However, it still faces some critical issues, one of which is the presence of toxic lead (Pb2+). Recent researches show that barium (Ba2+) can partially replace the Pb2+ in perovskite structure and achieve a promising device performance because of its adequate ionic radius. However, the optimal replacement amount of Ba2+ in perovskite is still limited. Herein, the methylammonium (MA)/formamidinium (FA) mixed‐cation perovskite is used as the active layer in PSCs and Pb2+ is partially substituted with Ba2+. Compared with the pure MA system, the best device efficiency can be achieved using higher Ba2+ replacement ratio. In addition, while introducing the appropriate polymer additive, the replacement ratio can be further increased without compromise of device efficiency. Using polyethylene glycol as polymer additive, 10.0 mol% Ba‐doped MA/FA mixed‐cation PSC with an efficiency of 16.1% can be realized. It is believed that this report provides an effective strategy to fabricate high‐performance lead‐reduced PSCs.

High Efficiency Quasi‐2D/3D Pb–Ba Perovskite Solar Cells via Phenethylammonium Chloride Addition

“…The average PCE of the PSC with MA 0.4 FA 0.6 Pb 0.9 Ba 0.1 I y Cl 3− y film is 15.0%. This efficiency performance is quite similar to our previous study [20b] . The lower fill factor (FF) may be attributed to the pinhole formation and incomplete surface coverage (Figure 2a).…”

“…The observation is consistent with our previous studies. [ 20 ] When x increased to 0.005, the pinholes on the surface of the perovskite film have significantly shrunk (Figure 2b). When the perovskite films were added the suitable amount of PEACl ( x = 0.01 and 0.03), some flake‐like and granular crystalline materials were formed between the perovskite grains (Figure 2c,d).…”

“…[ 19 ] The Pb–Ba perovskite with mixed cations (methylammonium (MA)/formamidinium (FA)) can effectively increase the stability of the material and eliminate hysteresis. [ 20 ] Therefore, the Pb–Ba perovskite materials have received some attention. [ 21 ] However, the amount of Pb replacement and efficiency of the device is often contradictory.…”

Role and Contribution of Polymeric Additives in Perovskite Solar Cells: Crystal Growth Templates and Grain Boundary Passivators

“…Wu et al used the MA/FA mixed‐cation perovskite as the active layer in PSCs in which Pb 2+ was only partially substituted with Ba 2+ . [ 82 ] Using PEO as the polymer additive, the PSC fabricated using a 10.0 mol% Ba‐doped MA/FA mixed‐cation perovskite exhibited a PCE of 16.1% (Table 3: Report E). Cai et al systematically studied the influence of three essentially different polymers on the performance of planar PSCs fabricated based on an MAPbI 3 perovskite layer and low‐temperature‐processed TiO 2 .…”

Improved Efficiency and Stability of Perovskite Solar Cells Using a Difluorobenzothiadiazole-Based Interfacial Material

“…The power conversion efficiency (PCE) of organic–inorganic perovskite solar cells (PSCs) has been boosted to over 25% in the past decade, thus attracting tremendous attention. , Organic–inorganic perovskite possesses a lot of advantages as a light harvester, such as a high absorption coefficient in the visible region, adjustable composition and properties, ambipolar charge transport ability, and solution processability, which is compatible with low-cost, large-area, and roll-to-roll manufacture. − On the other hand, the degradation of perovskite under moisture becomes one of the main drawbacks for commercial application, leading to insufficient long-term stability of PSCs. The water tolerance of perovskite can be moderately increased by composition engineering. − For example, the incorporations of Br – , Cs + , and SCN – are demonstrated to show improved moisture stability of the mixed perovskite in a high-humidity environment. − Hydroscopic polymer PEG is also employed in a perovskite film to bind MAI and prevent its escape in a humid atmosphere. , It is reported that 2D Ruddlesden-Popper perovskites containing diverse large alkylammonium cations exhibit higher hydrophobicity by inhibiting the ion migration . However, the stability of the perovskite often enhances at the expense of the enlargement of the band gap, which would impair the photovoltaic performance of the resultant devices .…”