Correlation of Changes in Electronic and Device Properties in Organic Photovoltaic with Exposure to Air. Issue 24 (20th November 2021)

• Record Type: Journal Article
• Authors: Yin, Yanting; Pan, Xun; Andersson, Mats R.; Lewis, David A.; Andersson, Gunther G.
• Is Part Of: Advanced materials interfaces. Volume 8:Issue 24(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-11-20
• Subjects: air exposure -- bulk heterojunction -- interface dipole -- MoO 3 -- organic photovoltaics; Materials science -- Periodicals; 620.11
• DOI: 10.1002/admi.202101657
• Languages: English
• ISSNs: 2196-7350

Abstract

Abstract: In polymer‐based organic photovoltaic cells, the capability of charge extraction/injection of molybdenum trioxide (MoO3 ) is demonstrated as interface layer for polymer bulk heterojunction (BHJ). The present work determines the dipole formed at the MoO3 and conjugated poly [2, 3‐bis (3‐octyloxyphenyl) quinoxaline‐5, 8‐diyl‐alt‐thiophene‐2, 5‐diyl] (TQ1):(6, 6)‐Phenyl C71 butyric acid methyl ester (PC71 BM) bulk heterojunction interface. This dipole has a major influence on the charge transport across the TQ1:PC71 BM interface. The formation of the dipole is determined with electron spectroscopy and the depth profiling technique neutral impact collision ion scattering spectroscopy. Metastable induced electron and UV‐photoelectron spectroscopy is applied to determine the enclosed surface coverage of minimum 1.5 nm MoO3 and a maximized dipole strength of 2.4 eV with >2 nm MoO3 deposition on BHJ. It is also demonstrated that the air exposure reduces the dipole at the interface and leads to a decrease in cell performance providing evidence that the dipole formed at the interface is beneficial for the functioning of photovoltaic cells. The results indicate that the reduction in dipole might not be the only mechanism leading to cell performance degradation. The findings of the present work have relevance for other BHJ systems because MoO3 as high work function material is likely to interact with other organic materials in a similar way. Abstract : A dipole is formed at the interface between MoO3 and poly [2, 3‐bis (3‐octyloxyphenyl) quinoxaline‐5, 8‐diyl‐alt‐thiophene‐2, 5‐diyl]/(6, 6)‐Phenyl C71 butyric acid methyl ester in organic photovoltaic devices. The dipole originates from the high work function of MoO3 relative to that of the BHJ and is 2.4 eV in strength. Further analysis reveals that the dipole deteriorates upon air exposure. The dipole deterioration correlates to the device performance.