Wang Na, Wu Yaqiong
Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China.
School of Metallurgical and Ecological Engineering, University of Science and Technology, Beijing 100083, China.
Materials (Basel). 2024 Feb 27;17(5):1091. doi: 10.3390/ma17051091.
CsPbI possesses three photoactive black phases (α, β, and γ) with perovskite structures and a non-photoactive yellow phase (δ) without a perovskite structure. Among these, α-CsPbI exhibits the best performance. However, it only exists at high temperatures and it tends to transform into the δ phase at room temperature, especially in humid environments. Therefore, the phase stability of CsPbI, especially in humid environments, is the main obstacle to its further development. In this study, we studied the interaction of HO with α-CsPbI and the intrinsic defects within it. It was found that the adsorption energy in the bulk is higher than that on the surface (-1.26 eV in the bulk in comparison with -0.60 eV on the surface); thus, HO is expected to have a tendency to diffuse into the bulk once it adsorbs on the surface. Moreover, the intrinsic vacancy of V in the bulk phase can greatly promote HO insertion due to the rearrangement of two I atoms in the two PbI octahedrons nearest to V and the resultant breaking of the Pb-I bond, which could promote the phase transition of α-CsPbI in a humid environment. Moreover, HO adsorption onto V contributes to a further distortion in the vicinity of V, which is expected to enhance the effect of V on the phase transition of α-CsPbI. Clarifying the interaction of HO with α-CsPbI and the intrinsic defects within it may provide guidance for further improvements in the stability of α-CsPbI, especially in humid environments.
CsPbI具有三种具有钙钛矿结构的光活性黑色相（α、β和γ）以及一种没有钙钛矿结构的非光活性黄色相（δ）。其中，α-CsPbI表现出最佳性能。然而，它仅在高温下存在，并且在室温下容易转变为δ相，尤其是在潮湿环境中。因此，CsPbI的相稳定性，尤其是在潮湿环境中的相稳定性，是其进一步发展的主要障碍。在本研究中，我们研究了HO与α-CsPbI及其内部固有缺陷的相互作用。结果发现，体相中的吸附能高于表面吸附能（体相为-1.26 eV，而表面为-0.60 eV）；因此，HO一旦吸附在表面，预计有扩散到体相中的趋势。此外，体相中的V固有空位可极大地促进HO插入，这是由于最靠近V的两个PbI八面体中的两个I原子重排以及由此导致的Pb-I键断裂，这可能促进α-CsPbI在潮湿环境中的相变。此外，HO吸附到V上会导致V附近进一步畸变，预计这会增强V对α-CsPbI相变的影响。阐明HO与α-CsPbI及其内部固有缺陷的相互作用可能为进一步提高α-CsPbI的稳定性提供指导，尤其是在潮湿环境中。
