A Simple Way to Simultaneously Release the Interface Stress and Realize the Inner Encapsulation for Highly Efficient and Stable Perovskite Solar Cells

Abstract

The mixed halide perovskites have become famous for their outstanding photoelectric conversion efficiency among new-generation solar cells. Unfortunately, for perovskites, little effort is focused on stress engineering, which should be emphasized for highly efficient solar cells like GaAs. Herein, polystyrene (PS) is introduced into the perovskite solar cells as the buffer layer between the SnO 2 and perovskite, which can release the residual stress in the perovskite during annealing because of its low glass transition temperature. The stress-free perovskite has less recombination, larger lattices, and a lower ion migration tendency, which significantly improves the cell's efficiency and device stability. Furthermore, the so-called inner-encapsulated perovskite solar cells are fabricated with another PS capping layer on the top of perovskite. As high as a 21.89% photoelectric conversion efficiency (PCE) with a steady-state PCE of 21.5% is achieved, suggesting that the stress-free cell can retain almost 97% of its initial efficiency after 5 days of "day cycle" stability testing.

Intermolecular π–π Conjugation Self‐Assembly to Stabilize Surface Passivation of Highly Efficient Perovskite Solar Cells

“…[ 9 ] A buffer layer, such as fullerene derivative, has been exploited to suppress interface defects by releasing interface stress. [ 10 ] Surface passivation by using organic ammonium salts such as phenethylammonium iodide (PEAI), can effectively eliminate surface halogen deficiency to promote the cell efficiency to exceeding 23%. [ 2a ] However, the stability issue of these coordination interactions or passivation effects is still seldom mentioned, which needs to be concerned because some passivation could be easily damaged under the erosion of the external environment.…”

Modification Engineering in SnO2 Electron Transport Layer toward Perovskite Solar Cells: Efficiency and Stability

“…To minimize the negative impact of tensile stress, increasing efforts have been made, including the annealing process optimization, the stress compensation effect, and the composition engineering of perovskite. [129][130][131][132] Wu et al [133] introduced polystyrene (PS) as a buffer layer between the SnO 2 and perovskite to slow down the stress effect at the heterojunction. The spin-coated PS layer on the SnO 2 significantly decreases the surface roughness from 5.12 to 1.55 nm.…”

“…Wu et al. [ 133 ] introduced polystyrene (PS) as a buffer layer between the SnO 2 and perovskite to slow down the stress effect at the heterojunction. The spin‐coated PS layer on the SnO 2 significantly decreases the surface roughness from 5.12 to 1.55 nm.…”

Strain Engineering of Metal–Halide Perovskites toward Efficient Photovoltaics: Advances and Perspectives

“…[ 10–12,13 ] Commonly, residual stress in semiconductor thin films could be caused by lattice mismatch, thermal stress, and external stimulus, and the accumulation of local stress in the semiconductor could eventually lead to the presence of point defects and dislocations. [ 14 ] These defects can further significantly promote the light‐, heat‐, and moisture‐induced chemical degradation and fracture of the semiconductor film. [ 15 ] What's worse, the generation of any defect will destroy the periodicity of the potential field of the crystal, thereby causing the scattering of carriers, greatly affecting the carrier mobility and local thermal characteristic in the crystal structure.…”