Low-Voltage, Low-Waste Fabrication of Semiconducting Thin Films by Continuous Flow Electrophoretic Deposition

太阳能广泛使用的最大障碍之一是太阳能电池组件的制造成本。电泳沉积利用电场将带电粒子驱动到表面，具有可伸缩性和低成本，为这一制造问题提供了一个引人注目的解决方案。该项目将研究无机半导体材料的电泳法沉积。该项目的目标是从由分散在溶剂中的纳米级半导体晶体组成的墨水中电泳法沉积薄膜。这项研究可能会带来廉价、高效和可持续的加工方法，用地球上丰富的无毒材料制造太阳能电池。该项目将为研究生和本科生提供尖端纳米制造工艺方面的多学科培训。研究成果和成果将在公共活动中分享，整合到讲座和基于实验室的本科课程中，并被带到当地一所公立学校的教室里。该项目的目标是使用胶体，全无机，纳米晶分散体，在极性，非水的电解液中进行低压电泳沉积。这一假设将被检验，即在电解液的电解与电泳颗粒的沉积相耦合的条件下，用于电泳沉积的阈值电压可以降低一个数量级至小于1伏。如此低的电压将导致传统反应堆的低沉积速率。因此，第二个假设将被检验，即通过电泳沉积微反应器连续流动纳米晶分散体可以获得高沉积速率和厚膜。可以调节流量、反应器几何形状和施加的偏压，以实现对纳米晶体原料的近乎完全的利用，并将废物产生降至最低。工作将集中在地球上丰富的、无毒的铜锌锡硫化物和硫化铅纳米晶体上，这些纳米晶体已经被用于最高效率的量子点太阳能电池。这项研究将加深对外加电场影响下的定向和自组装过程的理解，重点关注体相和纳米尺度带电表面交叉处化学反应离子的非平衡行为。具体地说，它将探索低电压下电泳沉积的基本机理。

One of the most significant impediments to the widespread use of solar energy is the manufacturing cost of the solar cell modules. Electrophoretic deposition, which uses an electric field to drive charged particles to a surface and which is scalable and low cost, presents a compelling solution to this manufacturing problem. This project will study electrophoretic deposition of inorganic semiconducting materials. The objective of this project is to electrophoretically deposit thin films from an ink comprised of nanometer-scale semiconductor crystals dispersed in a solvent. This research could lead to inexpensive, efficient, and sustainable processing methods for manufacturing solar cells from earth-abundant, non-toxic materials. The project will provide graduate and undergraduate students multidisciplinary training in cutting edge nanomanufacturing processes. The research results and accomplishments will be shared at public events, integrated into lectures and lab-based undergraduate courses and brought into the classrooms of a local public school. The objective of this project is to use colloidal, all-inorganic, nanocrystal dispersions in polar, non-aqueous electrolytes for low-voltage electrophoretic deposition. The hypothesis will be tested that the threshold voltage for electrophoretic deposition can be lowered by an order of magnitude to less than 1 volt under conditions in which electrolysis of the electrolyte is coupled with deposition of the electrophoresing particles. Such low voltages would lead to low deposition rates in conventional reactors. Therefore, a second hypothesis will be tested that continuously flowing the nanocrystal dispersion through an electrophoretic deposition microreactor can achieve both high deposition rate and thick films. Flow rate, reactor geometry, and applied bias can be tuned to achieve near-complete utilization of the nanocrystal feedstock and minimal waste generation. Work will focus on earth-abundant, non-toxic nanocrystals of copper zinc tin sulfide and lead sulfide, which have been used in the highest efficiency quantum dot solar cells. This research will deepen understanding of directed- and self-assembly processes under the influence of applied electric fields, focusing on the poorly understood, non-equilibrium behavior of chemically reactive ions at the intersection of bulk and nanoscale charged surfaces. Specifically it will probe the fundamental mechanism of electrophoretic deposition at low voltage.