Interface Engineering of Imidazolium Ionic Liquids toward Efficient and Stable CsPbBr₃ Perovskite Solar Cells

Abstract

The defect passivation of perovskite films is an efficacious way to further boost the power conversion efficiency (PCE) and long-term stability of perovskite solar cells (PSCs). In this work, ionic liquids (ILs) of 1-butyl-2,3-dimethylimidazolium chloride ([BMMIm]Cl) are used as a modification layer in perovskite films in carbon-based CsPbBr 3 PSCs without a hole-transporting material (HTM) for passivating the surface defects. The preliminary results demonstrate that the [BMMIm]Cl modifier passivates the surface defects of the perovskite film and reduces the valence band of perovskite close to the work function of the carbon electrode, which causes a remarkably inhibited nonradiative and radiative charge recombination, improved energy-level matching, and decreased energy loss. After optimization, a champion efficiency of 9.92% with a V oc as high as 1.61 V is achieved for the [BMMIm]Cl tailored carbon-based CsPbBr 3 PSC without HTM, which is improved by 61.3% in comparison with 6.15% for the control device. Furthermore, the encapsulation-free PSC presents good longterm stability after storage in an air atmosphere with 70% RH at 20 °C or 0% RH at 80 °C as well as under continuous illumination conditions for 30 days. The significantly improved PCE and stability in high humidity or temperature suggest that the perovskite passivation by ILs is an effective strategy for fabricating high-PCE and stable PSCs.

High‐Efficiency Carbon‐Based CsPbIBr2 Solar Cells with Interfacial Energy Loss Suppressed by a Thin Bulk‐Heterojunction Layer

“…[25] Generally, the growth of crystal grains perpendicular to the direction of the indium tin oxide (ITO)/TiO 2 substrate is more conducive to charge transfer. [26] This is also consistent with the vertical growth crystal grain morphology observed in the cross-sectional SEM image of CsPbIBr 2 in Figure 1c.…”

Examining the Interfacial Defect Passivation with Chlorinated Organic Salt for Highly Efficient and Stable Perovskite Solar Cells

“…It is remarkably efficient in suppressing the series resistance and improving the charge carriers’ dynamics by close contact modification between interlayers. [ 20 ] Figure 3b represents the current density–voltage ( J – V ) characteristics of MAPbI 3 PSCs with and without [BZTAm]Cl treatment, measured under standard simulated illumination of AM 1.5G (1000 Wm 2 ) and the corresponding device parameters are tabulated in Table 1 . The control device without [BZTAm]Cl modification acquired an average device PCE of 16.87% ± 1% with an open‐circuit voltage ( V OC ) of 1.07 ± 0.01 V, a current density ( J SC ) of 21.12 ± 1.29 mA cm −2 , and fill factor (FF) of 74% ± 1%.…”

“…[ 17 ] Moreover, previously reported work indicated that trap states mainly located at the interfaces of multilayers of whole device (called interface defects) and at the perovskite surface (called surface defects), which are effectively related to the energy level matching, hysteresis, charge carriers dynamics, and the long‐term environmental and operational stability. [ 18–22 ] Therefore, it is indispensable to explore an impressive way to diminish the defects, particularly at the interfaces, for acquiring the high‐efficient and stable PSCs. Currently, there are lots of approaches to improve the performance and stability of PSCs, containing additive engineering, using additive into a perovskite absorber layer and interface engineering, modifying the hole transport layer (HTL)/perovskite or perovskite/electron transport layer (ETL) interfaces.…”

All-inorganic CsPbBr3 perovskite: a promising choice for photovoltaics

“…However, most of ionic liquids such as methylammonium acetate [193] , 1-methyl-3imidazolium iodide [194] as 1-alkyl-4-amino-1,2,4-triazolium, [195],1-hexyl-3methylimidazolium chloride, [196] and 1-ethylpyridinium chloride [197], are incorporated in the perovskite solution which requires complex optimization processes as the blending system could undergo severe phase transition. The interface modification of CsPbBr 3 via incorporating Ionic liquid (IL) of 1-butyl-2,3-dimethylimidazolium chloride ([BMMIm]Cl) was studied by Zhang group [198]. In their study, they found out that the incorporation of ionic liquid modifier the surface defects of the films were passivated and the valence band of perovskite is shifted close to the work function of the carbon electrode, which substantially suppressed the radiative and improved energy-level matching, non-radiative charge recombination , and reduced energy loss.…”