Controlled Growth of Large Grains in CH₃NH₃PbI₃ Perovskite Films Mediated by an Intermediate Liquid Phase without an Antisolvent for Efficient Solar Cells

Abstract

High-quality crystalline large grains with uniform morphologies of the perovskite films are particularly important for achieving stable, high-performance perovskite solar cells. Herein, an effective strategy to control the growth of large grains in the CH3NH3PbI3 perovskite films is demonstrated by modifying the perovskite film deposition process through forming an intermediate CH3NH3PbI3·methylammonium chloride (MACl)·xCH3NH2 liquid phase induced by CH3NH2 gas treatment in combination with a MACl additive without an antisolvent. By tuning the incorporation of the MACl additive to the perovskite precursor solution, this intermediate liquid phase enables the well-controlled growth of large grains up to 3 μm, highly uniform morphology, and higher crystallinity in the final CH3NH3PbI3 perovskite films. The high-quality CH3NH3PbI3 film derived from the CH3NH3PbI3·MACl·xCH3NH2 phase leads to enhanced carrier lifetime and reduced charge-trap density and nonradiative recombination of the perovskite films. In addition, the defect healing and reduced grain boundaries also greatly improve the environmental stability in ambient air. The perovskite solar cells made via the CH3NH3PbI3·MACl·xCH3NH2 phase exhibit high power conversion efficiency of 18.4%, much higher than that of the perovskite solar cells made without MACl (15.8%).

N‐methyl‐2‐pyrrolidone Iodide as Functional Precursor Additive for Record Efficiency 2D Ruddlesden‐Popper (PEA)2(Cs)n−1PbnI3n+1 Solar Cells

“…These results further confirm the conclusion of PL spectrum that NMPI could retard the rapid crystallization rate to form a uniform morphology with fewer trap states and suppressed recombination. [8,53] Subsequently, the femtosecond transient absorption (fs-TA) measurements are conducted to study the photoinduced charge-transfer dynamics of quasi-2D CsPbI 3 , which is applied under a 400 nm laser pump excitation. Figure 4a,d shows the 3D plot TA spectrograms of quasi-2D (n = 20) CsPbI 3 , which is a function of delay time and wavelength.…”

“…These results further confirm the conclusion of PL spectrum that NMPI could retard the rapid crystallization rate to form a uniform morphology with fewer trap states and suppressed recombination. [ 8,53 ]…”

Unveiling the Effect of Potassium Treatment on the Mesoporous TiO2/ Perovskite Interface in Perovskite Solar Cells

“…The SCLC technique was applied to quantitatively evaluate the influence of the K treatment on the density of electronic trap states in the perovskite films with the configuration of FTO/c-TiO 2 /mesoporous TiO 2 without or with K treatment/perovskite/PCBM/Au, and the dark I – V curves are presented in Figure . In the dark I – V curves, the voltage between the Ohmic region and the trap-filled limit region is called the trap-filled limit voltage ( V TFL ), and the formula for estimating the trap state density is , where L , e , ε r , and ε 0 are the thickness of the perovskite film, the elementary charge, the dielectric constant, and the vacuum permittivity, respectively. , The V TFL values of the perovskite film deposited on pristine and K-treated mesoporous TiO 2 are 0.43 and 0.15 V, respectively. Thus, the trap state densities ( n t ) are estimated to be 8.30 × 10 14 and 2.38 × 10 15 cm –3 for the perovskite films deposited on K-treated mesoporous TiO 2 and pristine mesoporous TiO 2 , respectively.…”

“…, where L, e, ε r , and ε 0 are the thickness of the perovskite film, the elementary charge, the dielectric constant, and the vacuum permittivity, respectively. 48,49 The V TFL values of the perovskite film deposited on pristine and K-treated mesoporous TiO 2 are 0.43 and 0.15 V, respectively. Thus, the trap state densities (n t ) are estimated to be 8.30 × 10 14 and 2.38 × 10 15 cm −3 for the perovskite films deposited on K-treated mesoporous TiO 2 and pristine mesoporous TiO 2 , respectively.…”

What Happens at Surfaces and Grain Boundaries of Halide Perovskites: Insights from Reactive Molecular Dynamics Simulations of CsPbI$_{3}$

“…or carbonyl 57 and azo 58 containing ligands; ii) the grafting of surfaces with sterically hindering groups, such as phenylalkylammonium [59][60][61] and even bulkier organic groups; 62 (iii) optimizing the synthesis conditions, through the type of precursors, solvents, additives etc., to stimulate the growth of non-detrimental surface orientations, 63 reduce the formation of grain boundaries 64 and suppress the formation of defects altogether. 65 3 Computational details…”