Abstract
Black-colored (α, γ-phase) CsPbI3 perovskites have a small bandgap and excellent absorption properties in the visible light regime, making them attractive for solar cells. However, their long-term stability in ambient conditions is limited. Here, we demonstrate a strategy to improve structural and electrical long-term stability in γ-CsPbI3 by the use of an ultraviolet-curable polyethylene glycol dimethacrylate (PEGDMA) polymer network. Oxygen lone pair electrons from the PEGDMA are found to capture Cs+ and Pb2+ cations, improving crystal growth of γ-CsPbI3 around PEGDMA. In addition, the PEGDMA polymer network strongly contributes to maintaining the black phase of γ-CsPbI3 for more than 35 days in air, and an optimized perovskite film retained ~90% of its initial electrical properties under red, green, and blue light irradiation.
Highlights
Black-colored (α, γ-phase) CsPbI3 perovskites have a small bandgap and excellent absorption properties in the visible light regime, making them attractive for solar cells
We investigated in-depth the effect of the content of UV-cured polyethylene glycol dimethacrylate (PEGDMA) polymer network inside CsPbI3 thin film on the atmospheric stability of γ-CsPbI3
The PEGDMA (Mn ≈ 330) has short chain lengths with four repeating units, resulting in a dense network by the UV-curing, which acts to hold CsPbI3 tightly, it is possible to suppress the additional distortion of the γ-CsPbI3 lattice
Summary
Black-colored (α, γ-phase) CsPbI3 perovskites have a small bandgap and excellent absorption properties in the visible light regime, making them attractive for solar cells. Their long-term stability in ambient conditions is limited. The PEGDMA polymer network strongly contributes to maintaining the black phase of γ-CsPbI3 for more than 35 days in air, and an optimized perovskite film retained ~90% of its initial electrical properties under red, green, and blue light irradiation. To secure the long-term stability of the black phase CsPbI3 under ambient conditions, two approaches have been developed: partial substitution of anion or cation[25,26,27,28], and surface passivation using organic additives[29,30,31,32]. To evaluate the photo-electronic properties, two-terminal photoresistors were fabricated and evaluated, the optimized UV-cured γ-CsPbI3 (3 wt% PEGDMA) film showed that ~90% of the initial electrical values responding to red, green, and blue lights, were stably maintained even after 35 days in the ambient conditions
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