High-performance α-FAPbI3 perovskite solar cells with an optimized interface energy band alignment by a Zn(O,S) electron transport layer

• Published in: Journal of materials science. Materials in electronics 2023, Vol.34 (1), p.51, Article 51
• Main Authors: Madadi, Dariush, Gharibshahian, Iman, Orouji, Ali A.
• Format: Article
• Language: English
• Subjects: Absorbers; Alignment; Characterization and Evaluation of Materials; Chemistry and Materials Science; Circuits; Conduction bands; Electron transport; Energy bands; Energy levels; Materials Science; Open circuit voltage; Optical and Electronic Materials; Optimization; Perovskites; Photovoltaic cells; Quantum efficiency; Short circuit currents; Solar cells; Sulfur; Titanium dioxide
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1007/s10854-022-09565-z

Short-circuit current density (J sc ) losses in perovskite solar cells are one of the main bottlenecks despite the acceptable open-circuit voltage (V oc ) because of the suitable and wide bandgap of the absorber. A solution to reduce the J sc losses is introducing a suitable n -type electron transport layer (ETL) with a spike-like alignment at the ETL/absorber junction. In this paper, the Zn(O,S) ETL in α-FAPbI 3 perovskite cell has been proposed, and the impact of Zn(O,S) ETL on the performance cell has been investigated. The results indicate that the sulfur ratios in the proposed Zn(O,S) ETL substantially affect the optimization of energy levels of the conduction band at the α-FAPbI 3 /Zn(O,S) junction. The flexibility with ZnO 1− x S x ETL ranging from 60 to 70% sulfur makes it possible to form an ideal conduction band offset (CBO) at absorber/ETL junction in α-FAPbI 3 perovskite solar cells. Based on the external quantum efficiency (EQE), Zn(O,S) ETL with an efficient response to high-energy photons than conventional TiO 2 ETL reduces absorption losses and improves the J sc . The CBO of ~ 0.1 eV with a thin ZnO 0.35 S 0.65 on top of the α-FAPbI 3 absorber led to an increase of V oc to 1.21 V, J sc to 27.2 mA/cm 2 , and fill factor (FF) to 82%, resulting in an efficiency of 27%. According to impedance spectroscopy analysis, this improvement is related to the excellent transport of carriers across the α-FAPbI 3 /ZnO 0.35 S 0.65 interface due to the reduction of interface recombination by spike-like band alignment.