New Ternary Blend Strategy Based on a Vertically Self‐Assembled Passivation Layer Enabling Efficient and Photostable Inverted Organic Solar Cells

• Published in: Advanced science Vol. 10; no. 17; pp. e2206802 - n/a
• Main Authors: Jeong, Soyeong, Rana, Aniket, Kim, Ju‐Hyeon, Qian, Deping, Park, Kiyoung, Jang, Jun‐Ho, Luke, Joel, Kwon, Sooncheol, Kim, Jehan, Tuladhar, Pabitra Shakya, Kim, Ji‐Seon, Lee, Kwanghee, Durrant, James R., Kang, Hongkyu
• Format: Journal Article
• Language: English
• Published: Germany John Wiley & Sons, Inc 01.06.2023; John Wiley and Sons Inc; Wiley
• Subjects: Interfaces; inverted organic solar cells; Mass spectrometry; nonfullerene acceptor; Photocatalysis; photostability; Photovoltaic cells; Scientific imaging; self‐assembled monolayers; Zinc oxides; inverted organic solar cells; nonfullerene acceptor; photostability; self-assembled monolayers
• ISSN: 2198-3844; 2198-3844
• DOI: 10.1002/advs.202206802

Herein, a new ternary strategy to fabricate efficient and photostable inverted organic photovoltaics (OPVs) is introduced by combining a bulk heterojunction (BHJ) blend and a fullerene self‐assembled monolayer (C60‐SAM). Time‐of‐flight secondary‐ion mass spectrometry ‐ analysis reveals that the ternary blend is vertically phase separated with the C60‐SAM at the bottom and the BHJ on top. The average power conversion efficiency ‐ of OPVs based on the ternary system is improved from 14.9% to 15.6% by C60‐SAM addition, mostly due to increased current density (Jsc) and fill factor ‐. It is found that the C60‐SAM encourages the BHJ to make more face‐on molecular orientation because grazing incidence wide‐angle X‐ray scattering ‐ data show an increased face‐on/edge‐on orientation ratio in the ternary blend. Light‐intensity dependent Jsc data and charge carrier lifetime analysis indicate suppressed bimolecular recombination and a longer charge carrier lifetime in the ternary system, resulting in the enhancement of OPV performance. Moreover, it is demonstrated that device photostability in the ternary blend is enhanced due to the vertically self‐assembled C60‐SAM that successfully passivates the ZnO surface and protects BHJ layer from the UV‐induced photocatalytic reactions of the ZnO. These results suggest a new perspective to improve both performance and photostability of OPVs using a facial ternary method. A new ternary system is introduced that can form a vertically self‐assembled passivation layer on the interface between photoactive layer and ZnO layer in n‐i‐p device architecture. This system not only improves photostability against UV light but also increases in Jsc and fill factor ‐ by encouraging to make a favorable molecular orientation of photoactive materials from edge‐on to face‐on orientation.