Mo Sung-In, Choi Sungjin, An Jeong-Ho, Kim Bo-Jong, Min Kwan Hong, Park Sungeun, Hong Ji-Eun, Oh Soong Ju, Song Hee-Eun, Oh Joon-Ho, Kim Ka-Hyun
Ulsan Advanced Energy Technology R&D Center, Korea Institute of Energy Research, 44776 Ulsan, South Korea.
Department of Materials Science and Engineering, Korea University, 02841 Seoul, South Korea.
ACS Appl Mater Interfaces. 2023 Oct 11;15(40):46849-46860. doi: 10.1021/acsami.3c08957. Epub 2023 Sep 29.
A crystalline silicon (c-Si) solar cell with a polycrystalline silicon/SiO (poly-Si/SiO) structure, incorporating both electron and hole contacts, is an attractive choice for achieving ideal carrier selectivity and serving as a fundamental component in high-efficiency perovskite/Si tandem and interdigitated back-contact solar cells. However, our understanding of the carrier transport mechanism of hole contacts remains limited owing to insufficient studies dedicated to its investigation. There is also a lack of comparative studies on the poly-Si/SiO electron and hole contacts for ideal carrier-selective solar cells. Therefore, this study aims to address these knowledge gaps by exploring the relationship among microstructural evolution, dopant in-diffusion, and the resulting carrier transport mechanism in both the electron and hole contacts of poly-Si/SiO solar cells. Electron (n poly-Si/SiO/substrate)- and hole (p poly-Si/SiO/substrate)-selective passivating contacts are subjected to thermal annealing. Changes in the passivation properties and carrier transport mechanisms of these contacts are investigated during thermal annealing at various temperatures. Notably, the results demonstrate that the passivation properties and carrier transport mechanisms are strongly influenced by the microstructural evolution of the poly-Si/SiO layer stack and dopant in-diffusion. Furthermore, electron and hole contacts exhibit common behaviors regarding microstructural evolution and dopant in-diffusion. However, the hole contacts exhibit relatively inferior electrical properties overall, mainly because both the SiO interface and the p poly-Si are found to be highly defective. Moreover, boron in the hole contacts diffuses deeper than phosphorus in the electron contacts, resulting in deteriorated carrier collection. The experimental results are also supported by device simulation. Based on these findings, design rules are suggested for both electron and hole contacts, such as using thicker SiO and/or annealing the solar cell at a temperature not exceeding the critical annealing temperature of the hole contacts.
一种具有多晶硅/二氧化硅（poly-Si/SiO）结构且兼具电子和空穴接触的晶体硅（c-Si）太阳能电池，对于实现理想的载流子选择性并作为高效钙钛矿/硅叠层和叉指背接触太阳能电池的基本组件而言是一个有吸引力的选择。然而，由于专门针对空穴接触载流子传输机制的研究不足，我们对其的理解仍然有限。对于理想的载流子选择性太阳能电池，在多晶硅/二氧化硅电子和空穴接触方面也缺乏比较研究。因此，本研究旨在通过探索多晶硅/二氧化硅太阳能电池电子和空穴接触中的微观结构演变、掺杂剂内扩散以及由此产生的载流子传输机制之间的关系来填补这些知识空白。对电子（n型多晶硅/二氧化硅/衬底）和空穴（p型多晶硅/二氧化硅/衬底）选择性钝化接触进行热退火。研究在不同温度下热退火过程中这些接触的钝化性能和载流子传输机制的变化。值得注意的是，结果表明钝化性能和载流子传输机制受到多晶硅/二氧化硅层堆叠的微观结构演变和掺杂剂内扩散的强烈影响。此外，电子和空穴接触在微观结构演变和掺杂剂内扩散方面表现出共同行为。然而，空穴接触总体上表现出相对较差的电学性能，主要是因为发现二氧化硅界面和p型多晶硅都存在高度缺陷。而且，空穴接触中的硼比电子接触中的磷扩散得更深，导致载流子收集恶化。器件模拟也支持实验结果。基于这些发现，针对电子和空穴接触提出了设计规则，例如使用更厚的二氧化硅和/或将太阳能电池在不超过空穴接触临界退火温度的温度下退火。
