A Generally Applicable Approach Using Sequential Deposition to Enable Highly Efficient Organic Solar Cells

π-Extended Conjugated Polymer Acceptor Containing Thienylene–Vinylene–Thienylene Unit for High-Performance Thick-Film All-Polymer Solar Cells with Superior Long-Term Stability

The perylene diimide (PDI) chromophore is a classic polycyclic aromatic hydrocarbon that has been widely used in the field of organic electronics. A combination of strong visible light absorption and low-lying frontier molecular orbital (FMO) energy levels make PDI useful as a photoactive electron transporting material in organic solar cells. Indeed, PDI based molecules and polymers have been studied as so-called non-fullerene acceptors (NFAs) for over 30 years. Recent advances in materials design has enabled solution processed organic solar cell devices based on PDI materials to reach power conversion efficiencies (PCEs) upwards of 12%. This perspective highlights recent PDI design strategies developed to enable such highly performing devices and covers recent work on N-annulated PDIs, which have the potential to deliver roll-to-roll compatible processed solar cells with high operating voltages.

Perylene diimide based non-fullerene acceptors: top performers and an emerging class featuring N-annulation

Imidazole-Functionalized Imide Interlayers for High Performance Organic Solar Cells

Layer-by-layer (LbL) processing, otherwise known as sequential deposition, is emerging as the most promising strategy for fabrication of active layers in organic photovoltaic (OPV) devices on both laboratory and industrial scales. In comparison to the bulk heterojunction (BHJ) configuration, LbL facilitates separate and sequential deposition of each layer, enabling greater control and optimization of interfaces and final donor/acceptor morphology. Furthermore, this process encourages formation of an efficient vertical phase separation, where the acceptor and donor aggregations are largest at their respective electrodes, increasing exciton dissociation and transport while reducing unwanted charge recombination. Compared to BHJ OPVs, LbL OPVs are more robust, with less dependence on processing conditions, resulting in increased photo, thermal, and mechanical stability and greater power conversion efficiency retention when applied to large area modules. These advantages have resulted in significant interest in the LbL process and its potential to displace BHJ as the dominant process for large-scale OPV manufacturing. This review summarizes recent developments in OPV fabrication through LbL, with particular emphasis on material selection and thin film processing conditions.

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Layer-by-layer fabrication of organic photovoltaic devices: material selection and processing conditions

Hole transporting materials (HTMs) play a crucial role in achieving highly efficient and stable perovskite solar cells (PSCs). Spiro-typed materials being the most widely used HTMs are commonly uti...

Design of Low Crystallinity Spiro-Typed Hole Transporting Material for Planar Perovskite Solar Cells to Achieve 21.76% Efficiency

Spatially Orthogonal 2D Sidechains Optimize Morphology in All-Small-Molecule Organic Solar Cells

Developing efficient all-polymer solar cells (all-PSCs) has always been a long-standing challenge due to the unfavorable morphology caused by conventional blend casting (BC). Here, we first employ ...

Achieving Optimal Bulk Heterojunction in All-Polymer Solar Cells by Sequential Processing with Nonorthogonal Solvents

A perylene diimide-containing acceptor enables high fill factor in organic solar cells.

By analyzing the photovoltaic parameters of organic solar cells based on perylene diimide (PDI) acceptors, we found that the power conversion efficiencies (PCEs) showed an approximately positive linear correlation with the fill factors (FFs), which were mainly determined by the morphology. To tune the morphology impacted by the molecular geometry of the donor and the acceptor, a fully fused PDI derivative F-2PDI-4F, wherein the adjacent bay positions of PDI were substituted by fluorine atoms, was rationally designed and synthesized. The repulsion of F⋯F reduced the coplanarity of PDI and created a dihedral angle of 12.6°, which endowed F-2PDI-4F with relatively weak crystallinity as compared to its analogue F-2PDI without fluorination. These two acceptors were incorporated with two polymer donors, PTB7-Th and PBDB-T, with varied crystallinities to fabricate a solar cell device. The performance showed that the combination of a highly crystalline donor (acceptor) and a weakly crystalline acceptor (donor) was beneficial for the improvement in FF due to the improved microstructure of the blend films. Thus, the device with PBDB-T and F-2PDI-4F achieved a high FF of 66.9% and the best PCE of 9.05%. F-2PDI-4F is one of the few examples among numerous PDI acceptors that can achieve PCEs exceeding 9%. Our study provides a fruitful avenue for applying electrostatic repulsion to modulate molecular geometry, consequently improving the optoelectronic properties of organic semiconductors.

Kui Ding

Papers

Design of Low Crystallinity Spiro-Typed Hole Transporting Material for Planar Perovskite Solar Cells to Achieve 21.76% Efficiency

Spatially Orthogonal 2D Sidechains Optimize Morphology in All-Small-Molecule Organic Solar Cells

Achieving Optimal Bulk Heterojunction in All-Polymer Solar Cells by Sequential Processing with Nonorthogonal Solvents

A perylene diimide-containing acceptor enables high fill factor in organic solar cells.

Tailoring the molecular geometry of polyfluoride perylene diimide acceptors towards efficient organic solar cells