标题： 表面粗糙度对测量薄膜太阳能电池光电特性的影响 显示英文标题

标题： Impact of Surface Roughness in Measuring Optoelectronic Characteristics of Thin-Film Solar Cells

摘要： 薄膜吸收层的微观结构特性在开发高性能太阳能电池中起着至关重要的作用。扫描探针显微镜常用于测量薄膜太阳能电池的空间不均匀特性。虽然强大，但纳米级探针对样品的粗糙度很敏感，会在测量中引入复杂的信号和不必要的伪影。在这里，我们应用掠入射聚焦离子束（FIB）技术来降低CdTe的表面粗糙度，同时保留太阳能电池的次表面光电特性。我们比较了FIB抛光前后纳米尺度的光电特性。同时采集的开尔文探针力显微镜（KPFM）和原子力显微镜（AFM）图像显示，CdTe原始样品（峰谷粗糙度约为600 nm）的接触电位差（CPD）遵循表面形貌。相反，抛光后的CdTe（粗糙度约为20 nm）的CPD图与表面粗糙度无关。我们证明，光滑的CdTe表面还能实现分辨率远小于单个晶粒（<1微米）的高分辨率光致发光（PL）成像。我们的有限差分时域（FDTD）模拟说明了局部光激发如何与CdTe表面相互作用。我们的工作表明，低角度FIB抛光在研究薄膜太阳能电池的埋藏亚微结构特性时是有益的，需要注意近表面可能的离子束损伤。 显示英文摘要

摘要： Microstructural properties of thin-film absorber layers play a vital role in developing high-performance solar cells. Scanning probe microscopy is frequently used for measuring spatially inhomogeneous properties of thin-film solar cells. While powerful, the nanoscale probe can be sensitive to the roughness of samples, introducing convoluted signals and unintended artifacts into the measurement. Here, we apply a glancing-angle focused ion beam (FIB) technique to reduce the surface roughness of CdTe while preserving the subsurface optoelectronic properties of the solar cells. We compare the nanoscale optoelectronic properties before and after the FIB polishing. Simultaneously collected Kelvin-probe force microscopy (KPFM) and atomic force microscopy (AFM) images show that the contact potential difference (CPD) of CdTe pristine (peak-to-valley roughness of approximately 600 nm) follows the topography. In contrast, the CPD map of polished CdTe (roughness of approximately 20 nm) is independent of the surface roughness. We demonstrate the smooth CdTe surface also enables high-resolution photoluminescence (PL) imaging at a resolution much smaller than individual grains (< 1 micrometer). Our finite-difference time-domain (FDTD) simulations illustrate how the local light excitation interacts with CdTe surfaces. Our work supports low-angle FIB polishing can be beneficial in studying buried sub-microstructural properties of thin-film solar cells with care for possible ion-beam damage near the surface.