Managing Multiple Halide‐Related Defects for Efficient and Stable Inorganic Perovskite Solar Cells

Abstract

Halide-related surface defects on inorganic halide perovskite not only induce charge recombination but also severely limit the long-term stability of perovskite solar cells. Herein, adopting density functional theory calculation, we verify that iodine interstitials (I i ) has a low formation energy similar to that of the iodine vacancy (V I ) and is also readily formed on the surface of all-inorganic perovskite, and it is regarded to function as an electron trap. We screen a specific 2,6-diaminopyridine (2,6-DAPy) passivator, which, with the aid of the combined effects from halogen-N pyridine and coordination bonds, not only successfully eliminates the I i and dissociative I 2 but also passivates the abundant V I . Furthermore, the two symmetric neighboring -NH 2 groups interact with adjacent halides of the octahedral cluster by forming hydrogen bonds, which further promotes the adsorption of 2,6-DAPy molecules onto the perovskite surface. Such synergetic effects can significantly passivate harmful iodine-related defects and undercoordinated Pb 2 + , prolong carrier lifetimes and facilitate the interfacial hole transfer. Consequently, these merits enhance the power-conversion efficiency (PCE) from 19.6 % to 21.8 %, the highest value for this type of solar cells, just as importantly, the 2,6-DAPytreated CsPbI 3À x Br x films show better environmental stability.

Synergistic Surface Defect Passivation of Ionic Liquids for Efficient and Stable MAPbI3-Based Inverted Perovskite Solar Cells

“…Owing to either hydrogenbond formation or electrostatic forces, the iodide ions in the perovskite lattice coordinated with the diethylammonium cations, which shifted the binding-energy peaks, making the binding of DADA to the perovskite surface ions stronger. 38 In addition, the XPS C 1s spectrum (Figure S2) for the control perovskite thin film exhibits a clear C�O peak at 288.5 eV, which is attributed to carbon oxidation due to environmental exposure during the evaluation. In contrast, this C = O peak did not appear in the XPS C 1s spectra of the DADA-treated perovskite thin films, which indicates that DADA can protect perovskite films from the penetration of water and oxygen molecules and subsequent decomposition.…”

“…The I 3d peaks shifted from 618.3 eV (3d 5/2 ) and 629.8 eV (3d 3/2 ) to 619.0 and 630.4 eV for the control and DADA-treated perovskite thin films, respectively. Owing to either hydrogen-bond formation or electrostatic forces, the iodide ions in the perovskite lattice coordinated with the diethylammonium cations, which shifted the binding-energy peaks, making the binding of DADA to the perovskite surface ions stronger . In addition, the XPS C 1s spectrum (Figure S2) for the control perovskite thin film exhibits a clear CO peak at 288.5 eV, which is attributed to carbon oxidation due to environmental exposure during the evaluation.…”

Enhanced performance of perovskite solar cells via a bilateral electron-donating passivator as a molecule bridge

“…More importantly, according to previous works, the uncoordinated Pb 2+ of the [PbI 6 ] 4− octahedral and the electron-donating groups (–NH 2 /–OH) could form Lewis adducts through the interaction between the lone-pair electrons in them, and the formation of Lewis acid–base pairs of Pb 2+ with electron-donating groups helps to stabilize the [PbI 6 ] 4− octahedra. 28–30 Furthermore, the –NH 2 and –OH groups of HAL can connect with the iodide from [PbI 6 ] 4− octahedra via H-bond formation, which is also beneficial for the stabilization of [PbI 6 ] 4− octahedra at the buried interface of PVK. 31–33…”

Healing the Buried Interface by a Plant-Derived Green Passivator for Carbon-Based CsPbIBr2 Perovskite Solar Cells

“…Organic–inorganic hybrid perovskite solar cells (PSCs) have attracted extensive attention due to their unique semiconductor properties, such as long charge carrier diffusion length, tunable bandgap, high defect tolerance, and low exciton binding energies. − Within a very short time span, impressive achievements in photovoltaic applications have been made, and the certificated power conversion efficiency (PCE) of single-junction PSCs has been rapidly increased to 26.1%, which is comparable to that of Si-based solar cells. − However, the poor long-term operational stability still restricts their practical application, largely because of the usage of humidity-/heat-sensitive organic methylammonium and formamidinium. − Substituting organic cations with volatile-free Cs + to fabricate all-inorganic perovskites (CsPbX 3 , X = I, Br, Cl, or mixed) is an effective strategy to settle this issue. , Generally, there is a positive correlation between I doge and corresponding PCE owing to the reduced bandgap but a negative relationship for environmental stability. Although the efficiency of CsPbI 3 -based PSCs has exceeded 20%, the phase instability, which suffers from the phase conversion from the photoactive α-perovskite phase to the nonphotoactive β-perovskite phase, is still a great challenge for future deployment. ,, On the contrary, CsPbBr 3 exhibits the most superior stability, but its PCE is restricted by a narrower light-absorbing range . By balancing the stability and efficiency, the air-stable CsPbIBr 2 perovskite with a suitable bandgap ( E g = 2.10 eV) is regarded as one potential material in practical application for tandem photovoltaics. , …”