Graded bulk-heterojunction enables 17% binary organic solar cells via nonhalogenated open air coating

Abstract

Graded bulk-heterojunction (G-BHJ) with well-defined vertical phase separation has potential to surpass classical BHJ in organic solar cells (OSCs). In this work, an effective G-BHJ strategy via nonhalogenated solvent sequential deposition is demonstrated using nonfullerene acceptor (NFA) OSCs. Spin-coated G-BHJ OSCs deliver an outstanding 17.48% power conversion efficiency (PCE). Depth-profiling X-ray photoelectron spectroscopy (DP-XPS) and angle-dependent grazing incidence X-ray diffraction (GI-XRD) techniques enable the visualization of polymer/NFA composition and crystallinity gradient distributions, which benefit charge transport, and enable outstanding thick OSC PCEs (16.25% for 300 nm, 14.37% for 500 nm), which are among the highest reported. Moreover, the nonhalogenated solvent enabled G-BHJ OSC via open-air blade coating and achieved a record 16.77% PCE. The blade-coated G-BHJ has drastically different D-A crystallization kinetics, which suppresses the excessive aggregation induced unfavorable phase separation in BHJ. All these make G-BHJ a feasible and promising strategy towards highly efficient, eco- and manufacture friendly OSCs.

Volatile Solid Additive‐Assisted Sequential Deposition Enables 18.42% Efficiency in Organic Solar Cells

“…The relevant thick‐film and blade‐coated OSCs also show outstanding PCEs, respectively. [ 11 ] Very recently, Peng et al. introduced a wax additive to produce an interdigitated heterojunction morphology; an impressive PCE of 18.74%.…”

Spectroelectrochemically determined energy levels of PM6:Y6 blends and their relevance to solar cell performance

“…, in ternary blends. 39–44 The phase separation between the donor and acceptor plays a crucial role in efficient charge separation (exciton diffusion length is usually around 20 nm 45,46 ) and is influenced by the miscibility between PM6 and Y6 on the one hand. On the other hand, the properties of the chosen processing solvent and the processing method itself significantly impact the drying kinetics during film formation and therefore can influence the blend morphology.…”

Efficient semi-transparent organic solar cells enabled by a quasi-heterojunction active layer structure

“…1–3 Organic solar cells (OSCs) have attracted much attention in past decades as a competitive renewable energy source. 4–9 In particular, semi-transparent OSCs (ST-OSCs), which convert a certain part of sunlight into electrical energy and let the other part through, have potential applications in building-integrated photovoltaics and portable electronic devices. 10–13 Donor:acceptor blend bulk heterojunctions (BHJs) fabricated via one-step processing are the most prevalent active layer structures in opaque OSCs and ST-OSCs.…”