MAAc Ionic Liquid-Assisted Defect Passivation for Efficient and Stable CsPbIBr₂ Perovskite Solar Cells

Abstract

Cesium-based all-inorganic perovskite solar cells (PSCs), such as CsPbIBr 2 PSCs, have attracted wide attention for good thermal and wet stability, but the low open-circuit voltage (V oc ) mainly caused by the inadequate coverage of CsPbIBr 2 films is the main reason for limiting their development. The CsPbIBr 2 films grown on TiO 2 substrate directly have a large number of pinholes, which bring a lot of defects and lead to an increase of nonradiative recombination. In this work, a strategy extended for CsPbIBr 2 films by precoating methylammonium acetate (MAAc) ionic liquid onto a TiO 2 layer before depositing the CsPbIBr 2 film is demonstrated. The uniformly distributed MA + will be the nucleation center at the bottom of the CsPbIBr 2 film, which exhibited a notable impact on the crystallization kinetics of CsPbIBr 2 films. This effect simultaneously enhanced the crystal quality of the CsPbIBr 2 film and interfacial contact between the electron transporting layer (ETL) and CsPbIBr 2 layer. It is instrumental in decreasing the trap state density, suppressing nonradiative recombination, and extracting the charge carriers. Therefore, the stability of the optimized device has been improved considerably, and the champion power conversion efficiency (PCE) is up to 8.85% with a high V oc of 1.26 V. Benefiting from passivation, the PSC with 2 M MAAc IL interfacial modification remains 82% of its initial PCE after 30 days of exposing the device to ambient air at room temperature.

Robust Interfacial Modifier for Efficient Perovskite Solar Cells: Reconstruction of Energy Alignment at Buried Interface by Self‐Diffusion of Dopants

“…Organic lead halide perovskites (PVK) have proven to be competitive light-harvesting materials for photovoltaic devices owing to their superior photoelectric properties and simple To address these issues, different passivation molecules as modification layers were used in the buried interface of n-i-p structured PSCs, such as the ionic liquids, organic polymers and small molecules, [16][17][18][19][20] which markedly passivated the trap defects and improved the stability by the introduction of surface interaction with these defect charges or under-coordinated ionic components. In addition, researchers also modified the work function (W F ) of electron transport layers (ETLs) to regulate the mismatch of conduction band minimum (CBM) between ETLs and perovskites, thus alleviating the interface carrier recombination.…”

Ionic Liquid‐Assisted Crystallization and Defect Passivation for Efficient Perovskite Solar Cells with Enhanced Open‐Circuit Voltage

“…Although all parameters for the devices fabricated by DMII‐modified perovskite film have been enhanced obviously, the increase of the V OC was the most noticeable. The significant enhancement of V OC can be attributed to the fact that undercoordinated lead ions (Pb 2+ ) in perovskite film passivated effectively, and the detrimental PbI 2 on surfaces and at grain boundaries has also been substantially reduced [49] . The slight increase in J SC might be mainly due to the improved absorption ability in the visible light region for the cell composed of DMII‐modified perovskite film.…”

“…The significant enhancement of V OC can be attributed to the fact that undercoordinated lead ions (Pb 2 + ) in perovskite film passivated effectively, and the detrimental PbI 2 on surfaces and at grain boundaries has also been substantially reduced. [49] The slight increase in J SC might be mainly due to the ChemSusChem improved absorption ability in the visible light region for the cell composed of DMII-modified perovskite film. The higher FF value can be attributed to DMII-modified perovskite film with a higher quality, in which smooth and flat surface of perovskite film enabled better contact with the adjacent charge transport layer, leading to more efficient charge transfer and extraction at the interfaces.…”

Organic Molecules in All‐Inorganic CsPbIxBr3−xPerovskite Solar Cells: Interface Modifiers or Precursor Additives

“…As provided in Figure 7d, the uniformly distributed MA + will become the nucleation center at the bottom of the CsPbIBr 2 film by precoating the MAAc ionic liquid on the TiO 2 , which has a significant effect on the crystallization kinetics. [ 109 ] This effect simultaneously improves the crystal quality of the CsPbIBr 2 film and the interfacial contact between the ETL and the perovskite layer. It is beneficial to reduce the density of trap states, suppress nonradiative recombination, and extract carriers.…”