Influence of metal salts (Al, Ca, and Mg) on the work function and hole extraction at carbon counter electrodes in perovskite solar cells

Muna Fathiah Don; Piyasiri Ekanayake; James Robert Jennings; Hideki Nakajima; Udaya Kumar D; Chee Ming Lim

doi:10.1016/j.heliyon.2023.e17748

Influence of metal salts (Al, Ca, and Mg) on the work function and hole extraction at carbon counter electrodes in perovskite solar cells

Heliyon. 2023 Jun 28;9(7):e17748. doi: 10.1016/j.heliyon.2023.e17748. eCollection 2023 Jul.

Authors

Muna Fathiah Don¹, Piyasiri Ekanayake^{1

2}, James Robert Jennings^{1

2}, Hideki Nakajima³, Udaya Kumar D⁴, Chee Ming Lim⁵

Affiliations

¹ Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, Gadong BE 1410, Brunei Darussalam.
² Optoelectronic Device Research Group, Universiti Brunei Darussalam, Jalan Tungku Link, Gadong BE 1410, Brunei Darussalam.
³ Synchrotron Light Research Institute, 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand.
⁴ Department of Chemistry, National Institute of Technology Karnataka, Surathkal, India.
⁵ Centre for Advanced Material and Energy Sciences, Universiti Brunei Darussalam, Jalan Tungku Link, Gadong BE 1410, Brunei Darussalam.

Abstract

Hole transport material-free carbon-based perovskite solar cells (HTM-free C-PSCs) are recognized as a cost-effective and stable alternative to conventional perovskite solar cells. However, the significant energy level misalignment between the perovskite layer and the carbon counter electrode (CE) results in ineffective hole extraction and unfavorable charge recombination, which decreases the power conversion efficiency (PCE). Here, we report the introduction of metal salts (Al, Ca, and Mg) into graphite/carbon black (Gr/CB) CEs to modify the work function and enhance the hole selectivity of the CE. This modification leads to improved energy level alignment, efficient hole extraction, and reduced charge recombination. The PCE of the HTM-free C-PSC based on Al-modified Gr/CB as the CE material reached 9.91%, which is approximately 12% higher than that of devices employing unmodified Gr/CB CEs. This work demonstrates that by directly incorporating metal salts into the Gr/CB CE, the energy level alignment and hole extraction at the perovskite/carbon interface can be improved. This presents a viable method for enhancing the PCE of HTM-free C-PSCs.

Keywords: Carbon black; Carbon counter electrodes; Energy level alignment; Graphite; Metal salts; Perovskite solar cells; Work function tuning.