Synergistic Impact of Passivation and Efficient Hole Extraction on Phase Segregation in Mixed Halide Perovskites

The interface between the hole transport layer (HTL) and perovskite in p-i-n perovskite solar cells (PSCs) plays a vital role in the device performance and stability. However, the impact of this interface on the vertical phase segregation of mixed halide perovskite remains insufficiently understood. In this work, we systematically investigate the impact of chemical and electronic properties of HTL on vertical halide segregation of mixed-halide perovskites. We show that incorporating a PTAA/CuIxBr1-x bilayer as the HTL significantly suppresses light-induced vertical phase segregation in MAPb(I0.7Br0.3)3. We used grazing-incidence X-ray diffraction (GIXRD) to capture the depth-resolved composition change of MAPb(I0.7Br0.3)3 at the interface and within the bulk under illumination. By changing the illumination direction and the electronic properties of HTL, we elucidated the roles of charge carrier extraction and interfacial defects on vertical phase segregation. The PTAA/CuIxBr1-x bilayer, with its synergistic passivation and efficient hole extraction ability, stabilizes the interface and bulk of the mixed halide perovskite layer and prevents phase segregation. This work underscores that synergetic passivation and efficient hole extraction pack a more powerful punch for arresting the vertical phase segregation in mixed-halide perovskite.

在p-i-n型钙钛矿太阳能电池（PSCs）中，空穴传输层（HTL）与钙钛矿之间的界面对器件性能及稳定性起着至关重要的作用。然而，该界面对混合卤化物钙钛矿垂直相分离的影响尚未得到充分理解。本研究系统地探究了HTL的化学与电子特性对混合卤化物钙钛矿垂直卤化物分离的影响。研究表明，采用PTAA/CuIₓBr₁₋ₓ双层结构作为HTL可显著抑制MAPb(I₀.₇Br₀.₃)₃中光诱导的垂直相分离。我们利用掠入射X射线衍射（GIXRD）捕捉了光照下MAPb(I₀.₇Br₀.₃)₃在界面及体相内的深度分辨成分变化。通过改变光照方向及HTL的电子特性，我们阐明了电荷载流子提取与界面缺陷在垂直相分离中的作用。PTAA/CuIₓBr₁₋ₓ双层结构凭借其协同钝化及高效空穴提取能力，可稳定混合卤化物钙钛矿层的界面与体相，并抑制相分离。本研究强调，协同钝化与高效空穴提取对遏制混合卤化物钙钛矿的垂直相分离具有更强的效果。