Lin Yida, Gao Tina, Pan Xiaoyun, Kamenetska Maria, Thon Susanna M
Department of Electrical and Computer Engineering, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD, 21218, USA.
Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, MA, 02215, USA.
Adv Mater. 2020 Mar;32(11):e1906602. doi: 10.1002/adma.201906602. Epub 2020 Feb 3.
The morphology, chemical composition, and electronic uniformity of thin-film solution-processed optoelectronics are believed to greatly affect device performance. Although scanning probe microscopies can address variations on the micrometer scale, the field of view is still limited to well under the typical device area, as well as the size of extrinsic defects introduced during fabrication. Herein, a micrometer-resolution 2D characterization method with millimeter-scale field of view is demonstrated, which simultaneously collects photoluminescence spectra, photocurrent transients, and photovoltage transients. This high-resolution morphology mapping is used to quantify the distribution and strength of the local optoelectronic property variations in colloidal quantum dot solar cells due to film defects, physical damage, and contaminants across nearly the entire test device area, and the extent to which these variations account for overall performance losses. It is found that macroscopic defects have effects that are confined to their localized areas, rarely prove fatal for device performance, and are largely not responsible for device shunting. Moreover, quantitative analysis based on statistical partitioning methods of such data is used to show how defect identification can be automated while identifying variations in underlying properties such as mobilities and recombination strengths and the mechanisms by which they govern device behavior.
人们认为，通过溶液处理的薄膜光电器件的形态、化学成分和电子均匀性会极大地影响器件性能。尽管扫描探针显微镜可以检测微米尺度上的变化，但视场仍然局限于远小于典型器件面积以及制造过程中引入的外在缺陷的尺寸。在此，展示了一种具有毫米级视场的微米分辨率二维表征方法，该方法同时收集光致发光光谱、光电流瞬变和光电压瞬变。这种高分辨率形态映射用于量化胶体量子点太阳能电池中由于薄膜缺陷、物理损伤和污染物导致的局部光电性能变化的分布和强度，这些变化几乎覆盖整个测试器件区域，以及这些变化对整体性能损失的影响程度。研究发现，宏观缺陷的影响局限于其局部区域，很少对器件性能造成致命影响，并且在很大程度上与器件短路无关。此外，基于此类数据的统计划分方法的定量分析用于展示如何在识别迁移率和复合强度等潜在特性变化及其控制器件行为的机制的同时实现缺陷识别的自动化。
