Sb2S3 solar cells with TiO2 electron transporting layers synthesized by ALD and USP methods
Tatjana Dedova, Robert Krautmann, Marin Rusu, Atanas Katerski, Malle Krunks, Thomas Unold, Nicolae Spalatu, Arvo Mere, J. Sydorenko, Maciej Sibiński, Ilona Oja Açik
Abstract
Electronic characteristics were investigated for solar cells (SCs) based on FTO/TiO 2 /Sb 2 S 3 /P3HT/Au structure, employing TiO 2 electron transport layers (ETLs) fabricated by two different methods: ultrasonic spray pyrolysis (USP) and atomic layer deposition (ALD). Regardless of the deposition method, both ALD and USP-TiO 2 exhibit the anatase crystal structure. The calculated crystallite sizes, derived from the (101) reflection of TiO 2 layers using the Scherrer equation, show minimal variance between the two methods, with values 25 nm for USP and 30 nm for ALD TiO 2 , respectively. Optical band gaps (E g ) were found to be 3.31 eV and 3.35 eV for USP and ALD methods, respectively. Exploring the thickness series of ALD-TiO 2 , ranging from 100 to 1000 cycles (approximately 5–75 nm), solar cell performance was evaluated, with the highest power conversion efficiency (PCE) of 3.3 % achieved using ALD-TiO 2 of 400 cycles (approximately 30 nm thick). Notably, SCs featuring USP TiO 2 ETL layers, with a thickness of approximately 35–40 nm, outperform their ALD-TiO 2 counterparts, improving PCE by 15 %, recording 4.0 % versus 3.3 %, respectively. This superiority in PCE is attributed to the more favorable conduction band minimum (CBM) position of USP-TiO 2 relative to the Fermi level, as revealed in the band diagram. Specifically, a lower CBM spike at the USP-TiO 2 /-Sb 2 S 3 interface indicates reduced recombination rates compared to those at the ALD-TiO 2 /-Sb 2 S 3 interface. This study offers valuable insights into enhancing SC performance by optimizing deposition methods and synthesis parameters of ETL layers. • Sb 2 S 3 solar cells with TiO 2 electron transporting layers synthesized by ALD and USP methods are studied. • 15 % boost in performance of SC based on USP-TiO 2 ETL layers. • The lower CBM spike at the USP-TiO 2 /Sb 2 S 3 interface indicates a reduced recombination rate. • USP-TiO 2 is cost-effective and high-quality ETL for thin film Sb 2 S 3 solar cells.