Unraveling High Reproducibility and Broad Composition Tolerance in High‐Efficiency Organic Solar Cells via Sequential Deposition

Abstract

The reproducibility issue is impeding the progress of commercialization in organic photovoltaic (OPV) devices, as the difficulty in precise micro‐nano structure control in bulk heterojunction films, as well as the ineluctable fluctuations of molecular weight and polydispersity index in the synthetic process. Due to such intrinsic properties, the poor regioregularity significantly affects the batch‐to‐batch variation in performance of large‐area or integrative scattered OPV devices. Seeking alternatives as compensatory strategies is expected to reduce the inevitable problem of reproducibility in the fabrication process. Herein, the application potential of a pseudo‐bilayer structure in high‐performance OPVs, by using the solution‐processed method is thoroughly examined, and it is observed that the sequentially‐deposited solar cells enjoy improve device reproducibility in addition to the power conversion efficiency (PCE) enhancement. Importantly, such desirable reproducibility in layer‐by‐layer structures raised from the film formation process provides new opportunities in ternary OPV devices, and an improved PCE of 18.70% can be achieved in a PM6/L8‐BO:PY‐IT device, where the counterpart ternary cases exhibit a decreasing trend in performance with the increasing content of PY‐IT. This work illustrates the spatial effects of pseudo‐bilayer OPV devices in the aspect of charge carrier transport/transfer, morphology and film formation kinetics, and provides a novel perspective to overcome the barriers to commercialization.

Over 19.2% efficiency of layer-by-layer organic photovoltaics enabled by a highly crystalline material as an energy donor and nucleating agent

“…The LbL active layers suffered from soft plasma peeling off by oxygen glow discharge. The FLAS characterization was performed to explore the component variation in LbL film dependence on the peeling time, 57,58 as displayed in Fig. 7a–c.…”

Correlating Aggregation Ability of Polymer Donors with Film Formation Kinetics for Organic Solar Cells with Improved Efficiency and Processability

“…[26,27] Various recent works reported that the film formation kinetics would be significantly affected by device fabrication conditions, such as the processing solvents, the introduction of solid additives, and the processing temperatures. [28][29][30][31][32] For the influence of more basic material properties, such as donor aggregation ability, on film formation kinetics, however, although the conclusions drawn from it would provide important guidance for molecular designs, few studies have touched upon it. Therefore, correlating the aggregation ability of polymer donors with film formation kinetics may lead to efficient devices and some meaningful guidance.…”

Over 17.1% or 18.2% Efficiency of Layer-by-Layer All-Polymer Solar Cells via Incorporating Efficient Pt Complexes as Energy Donor Additive

“…At present, binary all-polymer organic solar cells have achieved a PCE close to 19% . Layer-by-layer (LbL) active layers were prepared by sequential spin-coating technology, which endows the active layers with favorable vertical composition distribution, tunable D/A interfaces and high phase purity in donor or acceptor layer. , Some key scientific issues should be further clarified, such as exciton diffuse distance and exciton utilization efficiency near electrodes. − The efficient exciton dissociation in LbL APSCs is a challenge due to the quite limited exciton diffusion distance in organic materials and the relatively small donor/acceptor interface in LbL devices. − Some smart strategies of enhancing LbL exciton dissociation focus on increasing the interface of donor layer and acceptor layer, such as enlarging component interdiffusion between donor and acceptor layers by solvent additive, introducing dissociation strengthening layer (DSL) or employing donor incorporation into acceptor layer (DIA) strategy. − Wang et al developed a diluted heterojunctions strategy in which APSC of diluting PM6 with 1 wt % PY-IT and diluting PY-IT with 1 wt % D18 achieved a high PCE of 19.4% . It is well-known that exciton diffusion distance strongly depends on the exciton lifetime of donors and acceptors, which should be prolonged by increasing the exciton lifetime of donors and acceptors through incorporating efficient triplet materials with long emission lifetime.…”