Organic Solar Cells Based on WO2.72 Nanowire Anode Buffer Layer with Enhanced Power Conversion Efficiency and Ambient Stability

Tungsten oxide as an alternative to conventional acidic PEDOT:PSS has attracted much attention in organic solar cells (OSCs). However, the vacuum-processed WO 3 layer and high-temperature sol–gel hydrolyzed WO X are incompatible with large-scale manufacturing of OSCs. Here, we report for the first time that a specific tungsten oxide WO 2.72 (W 18 O 49 ) nanowire can function well as the anode buffer layer. The nw-WO 2.72 film exhibits a high optical transparency. The power conversion efficiency (PCE) of OSCs based on three typical polymer active layers PTB7:PC 71 BM, PTB7-Th:PC 71 BM, and PDBT-T1:PC 71 BM with nw-WO 2.72 layer were improved significantly from 7.27 to 8.23%, from 8.44 to 9.30%, and from 8.45 to 9.09%, respectively compared to devices with PEDOT:PSS. Moreover, the photovoltaic performance of OSCs based on small molecule p -DTS(FBTTh 2 ) 2:PC 71 BM active layer was also enhanced with the incorporation of nw-WO 2.72 . The enhanced performance is mainly attributed to the improved short-circuit current density ( J sc ), which benefits from the oxygen vacancies and the surface apophyses for better charge extraction. Furthermore, OSCs based on nw-WO 2.72 show obviously improved ambient stability compared to devices with PEDOT:PSS layer. The results suggest that nw-WO 2.72 is a promising candidate for the anode buffer layer materials in organic solar cells.