title: Energy Level Tuning of Non-Fullerene Acceptors in Organic Solar Cells.
abstract: The use of non-fullerene acceptors in organic photovoltaic (OPV) devices could lead to enhanced efficiencies due to increased open-circuit voltage (VOC) and improved absorption of solar light. Here we systematically investigate planar heterojunction devices comprising peripherally substituted subphthalocyanines as acceptors and correlate the device performance with the heterojunction energetics. As a result of a balance between VOC and the photocurrent, tuning of the interface energy gap is necessary to optimize the power conversion efficiency in these devices. In addition, we explore the role of the charge transport layers in the device architecture. It is found that non-fullerene acceptors require adjusted buffer layers with aligned electron transport levels to enable efficient charge extraction, while the insertion of an exciton-blocking layer at the anode interface further boosts photocurrent generation. These adjustments result in a planar-heterojunction OPV device with an efficiency of 6.9% and a VOC above 1 V.
authors.affiliation: †ESAT, KU Leuven, Kasteelpark Arenberg 10, B-3001 Leuven, Belgium.|‡Imec, Kapeldreef 75, B-3001 Leuven, Belgium.
authors.forename: Kjell
authors.initials: K
authors.lastname: Cnops
authors.affiliation: §Department of Organic Chemistry, Universidad Autónoma de Madrid, c/Francisco Tomás y Valiente 7, Cantoblanco, 28049 Madrid, Spain.
authors.forename: German
authors.initials: G
authors.lastname: Zango
authors.affiliation: †ESAT, KU Leuven, Kasteelpark Arenberg 10, B-3001 Leuven, Belgium.|‡Imec, Kapeldreef 75, B-3001 Leuven, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: Genoe
authors.affiliation: †ESAT, KU Leuven, Kasteelpark Arenberg 10, B-3001 Leuven, Belgium.|‡Imec, Kapeldreef 75, B-3001 Leuven, Belgium.
authors.forename: Paul
authors.initials: P
authors.lastname: Heremans
authors.affiliation: §Department of Organic Chemistry, Universidad Autónoma de Madrid, c/Francisco Tomás y Valiente 7, Cantoblanco, 28049 Madrid, Spain.
authors.forename: M Victoria
authors.initials: MV
authors.lastname: Martinez-Diaz
authors.affiliation: §Department of Organic Chemistry, Universidad Autónoma de Madrid, c/Francisco Tomás y Valiente 7, Cantoblanco, 28049 Madrid, Spain.|∥IMDEA-Nanociencia, c/Faraday 9, Campus de Cantoblanco, 28049 Madrid, Spain.
authors.forename: Tomas
authors.initials: T
authors.lastname: Torres
authors.affiliation: ‡Imec, Kapeldreef 75, B-3001 Leuven, Belgium.
authors.forename: David
authors.initials: D
authors.lastname: Cheyns