• Ali, Fawad
• Tiong, Vincent
• Wang, Hongxia
• Fan, Lijuan

Abstract

Perovskite solar cells utilize metal oxide thin films as electronic transport for high performance devices. These electronic transport metal oxides are generally processed at higher temperatures. In this research we report room temperature processed WO3-x thin film as electron transport layer for high performance and low hysteresis device. High oxygen deficient WO3-x film was deposited at room temperature using e-beam evaporation in high vacuum condition. For comparison, the amount of oxygen vacancies was reduced by post-annealing of the as-deposited WO3-x films at 300 oC for 1 hour in air. XRD and Raman measurements showed no WO3-x characteristic peak of both the as-deposited and annealed films. From XPS and EPR, the as-deposited film shows large amount of oxygen vacancies compared to the post-annealed film. The bandgap of the post-annealed film increases due to reduced conductivity and thus a reduction in the device performance, mainly because of the low Voc and high current-voltage hysteresis in the forward and reverse scans. The perovskite solar cell device developed using the room temperature deposited electron transport WO3-x layer has shown low current-voltage hysteresis. This device achieved a power conversion efficiency of 10.3% and hysteresis index of 2.1%. This work demonstrates the feasibility of WO3-x film as electron transport layer for high efficiency perovskite solar cell with reduced hysteresis fabricated at low temperature using industrially viable e-beam evaporation method.

Topics

• perovskite
• x-ray diffraction
• thin film
• x-ray photoelectron spectroscopy
• Oxygen
• electron spin resonance spectroscopy
• annealing
• evaporation
• power conversion efficiency