Improving the Open-Circuit Voltage of Sn-Based Perovskite Solar Cells by Band Alignment at the Electron Transport Layer/Perovskite Layer Interface

Tomoyasu Yokoyama; Yu Nishitani; Yumi Miyamoto; Shohei Kusumoto; Ryusuke Uchida; Taisuke Matsui; Kenji Kawano; Takashi Sekiguchi; Yukihiro Kaneko

doi:10.1021/acsami.0c04676

Improving the Open-Circuit Voltage of Sn-Based Perovskite Solar Cells by Band Alignment at the Electron Transport Layer/Perovskite Layer Interface

ACS Appl Mater Interfaces. 2020 Jun 17;12(24):27131-27139. doi: 10.1021/acsami.0c04676. Epub 2020 Jun 2.

Authors

Tomoyasu Yokoyama¹, Yu Nishitani¹, Yumi Miyamoto¹, Shohei Kusumoto¹, Ryusuke Uchida¹, Taisuke Matsui¹, Kenji Kawano¹, Takashi Sekiguchi¹, Yukihiro Kaneko¹

Affiliation

¹ Technology Innovation Division, Panasonic Corporation, 3-1-1 Yagumo-nakamachi, Moriguchi City, Osaka 570-8501, Japan.

PMID: 32427458
DOI: 10.1021/acsami.0c04676

Abstract

Organic-inorganic lead halide perovskites are promising materials for realization of low-cost and high-efficiency solar cells. Because of the toxicity of lead, Sn-based perovskite materials have been developed as alternatives to enable fabrication of Pb-free perovskite solar cells. However, the solar cell performance of Sn-based perovskite solar cells (Sn-PSCs) remains poor because of their large open-circuit voltage (V_OC) loss. Sn-based perovskite materials have lower electron affinities than Pb-based perovskite materials, which result in larger conduction band offset (CBO) values at the interface between the Sn-based perovskite and a conventional electron transport layer (ETL) material such as TiO₂. Herein, the relationship between the V_OC and the CBO in these devices was studied to improve the solar cell performances of Sn-PSCs. It was found that the band offset at the ETL/perovskite layer interface affects the V_OC of the Sn-PSCs significantly but does not affect that of the Pb-PSCs because the Sn-based perovskite material is a p-type semiconductor, unlike the Pb-based perovskite. It was also found that Nb₂O₅ has the CBO that is closest to zero for Sn-based perovskite materials, and the V_OC values of Sn-PSCs that use Nb₂O₅ as their ETL are higher than those of Sn-PSCs using TiO₂ or SnO₂ ETLs. This study indicates that control of the energy alignment at the ETL/perovskite layer interface is an important factor in improving the V_OC values of Sn-PSCs.

Keywords: band alignment; conduction band offset; electron transport layer; formamidinium tin iodide; lead-free; niobium oxide; open-circuit voltage; perovskite solar cells.