Design Rule of Electron- and Hole-Selective Contacts for Polycrystalline Silicon-Based Passivating Contact Solar Cells

Sung-In Mo; Sungjin Choi; Jeong-Ho An; Bo-Jong Kim; Kwan Hong Min; Sungeun Park; Ji-Eun Hong; Soong Ju Oh; Hee-Eun Song; Joon-Ho Oh; Ka-Hyun Kim

doi:10.1021/acsami.3c08957

Design Rule of Electron- and Hole-Selective Contacts for Polycrystalline Silicon-Based Passivating Contact Solar Cells

ACS Appl Mater Interfaces. 2023 Oct 11;15(40):46849-46860. doi: 10.1021/acsami.3c08957. Epub 2023 Sep 29.

Authors

Sung-In Mo^{1

2}, Sungjin Choi³, Jeong-Ho An^{1

2}, Bo-Jong Kim⁴, Kwan Hong Min³, Sungeun Park³, Ji-Eun Hong¹, Soong Ju Oh², Hee-Eun Song³, Joon-Ho Oh¹, Ka-Hyun Kim⁴

Affiliations

¹ Ulsan Advanced Energy Technology R&D Center, Korea Institute of Energy Research, 44776 Ulsan, South Korea.
² Department of Materials Science and Engineering, Korea University, 02841 Seoul, South Korea.
³ Photovoltaics Research Department, Korea Institute of Energy Research, 34129 Daejeon, South Korea.
⁴ Department of Physics, Chungbuk National University, 28644 Cheongju, South Korea.

PMID: 37773933
DOI: 10.1021/acsami.3c08957

Abstract

A crystalline silicon (c-Si) solar cell with a polycrystalline silicon/SiO_x (poly-Si/SiO_x) 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_x 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_x solar cells. Electron (n⁺ poly-Si/SiO_x/substrate)- and hole (p⁺ poly-Si/SiO_x/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_x 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_x 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_x and/or annealing the solar cell at a temperature not exceeding the critical annealing temperature of the hole contacts.

Keywords: SiOx; carrier transport; carrier-selective passivating contact; crystalline silicon solar cell; dopant in-diffusion; microstructure evolution; polycrystalline silicon.