Cesium lead iodide (CsPbI3) with a bandgap of ~1.7 eV is an attractive material for use as a wide-gap perovskite in tandem perovskite solar cells due to its single halide component, which is capable of inhibiting halide segregation. However, phase transition into a photo inactive δ-CsPbI3 at room temperature significantly hinders performance and stability. Thus, maintaining the photo-active phase is a key challenge because it determines the reliability of the tandem device. The dimethylammonium (DMA)-facilitated CsPbI3, widely used to fabricate CsPbI3, exhibits different phase transition behaviors than pure CsPbI3. Here, we experimentally investigated the phase behavior of DMA-facilitated CsPbI3 when exposed to external factors, such as heat and moisture. In DMA-facilitated CsPbI3 films, the phase transition involving degradation was observed to begin at a temperature of 150 °C and a relative humidity of 65 %, which is presumed to be related to the sublimation of DMA. Forming a closed system to inhibit the sublimation of DMA significantly improved the phase transition under the same conditions. These results indicate that management of DMA is a crucial factor in maintaining the photo-active phase and implies that when employing DMA designs are necessary to ensure phase stability in DMA-facilitated CsPbI3 devices.

1. 서 론
2. 실험 방법
    2.1. 시약
    2.2. 페로브스카이트 박막 제작 및 봉지화 방법
    2.3. 분석법
3. 결과 및 고찰
    3.1. 열에 의한 상안정성
    3.2. 수분에 의한 상안정성
    3.3. 상안정화를 위한 격자 유지 방안
4. 결 론
Acknowledgement

• 강소현(고려대학교 건축사회환경공학부 학생) | Sohyun Kang (School of Civil, Environmental and Architectural Engineering, Korea University, Seoul 02841, Republic of Korea)
• 이승민(고려대학교 건축사회환경공학부 학생) | Seungmin Lee (School of Civil, Environmental and Architectural Engineering, Korea University, Seoul 02841, Republic of Korea)
• 노준홍(고려대학교 건축사회환경공학부 교수) | Jun Hong Noh (School of Civil, Environmental and Architectural Engineering, Korea University, Seoul 02841, Republic of Korea) Corresponding author