In Situ Absorption Characterization Guided Slot‐Die‐Coated High‐Performance Large‐Area Flexible Organic Solar Cells and Modules

Abstract

The PCEs of small-area single junction OSCs have reached over 19%, providing an essential foundation for scaling up. [16][17][18] However, these devices with an effective area smaller than 0.1 cm 2 are usually fabricated by the spin-coating method on glassindium tin oxide (ITO) substrates, which limits the further upscale continuous production due to the associated uneven linear speed. Large-area coating methods, such as spray coating, [16] blade coating, [17][18][19] slot-die coating, [20][21][22] inkjet printing, [23] etc., are widely used in the scalable fabrication of large-area OSCs. Due to its advantages of easy operation, low material waste, and high throughput, the slot-die coating process is considered one of the most promising approaches in the field of largearea OSCs and has the potential for further roll-to-roll (R2R) production. [24][25][26][27][28] Recently, many studies revealed that the solvent drying process in the slot-die coating is much slower than that in spin coating, leading to a significant change in the nanoscale morphology of the photoactive layers. [29] Various efforts have been devoted to optimizing the slot-die coating methodology for fabricating high-efficiency OSCs. Early in 2014, Zhan et al. focused on the drying mechanism in the spin-coating and roll-coated methods by comparing the amount of additive, demonstrating the importance of the individual optimization approach in the large-area coating process. [30] By synergistic optimization of slot-die coating conditions, our group successfully acquired high-efficiency flexible devices, which maintain over 98% PCE of the small-area rigid devices. [31] Besides the coating condition optimization, tremendous efforts have been made to investigate the aggregation during the coating process. Ma et al. revealed that processing conditions could affect the phase-separation kinetics of donors and acceptors in the active layer, such as coating temperature and solution temperature. [32,33] Molecular aggregation ability significantly influences film formation kinetics of the active layer, while its influence on slot-die coating fabrication has seldom been investigated. Recently, we developed two acceptors with low reorganization energy, i.e., Qx-1 and Qx-2, and the spin-coated small-area devices of PM6:Qx-1 and PM6:Qx-2 fabricated using chloroform showed similar device performance (≈18%) due to their similar molecular structure. [34] Slot-die coating is recognized as the most compatible method for the roll-toroll (R2R) processing of large-area flexible organic solar cells (OSCs). However, the photovoltaic performance of large-area flexible OSC lags significantly behind that of traditional spin-coating devices. In this work, two acceptors, Qx-1 and Qx-2, show quite different film-formation kinetics in the slot-die coating process. In situ absorption spectroscopy indicates that the excessive crystallinity of Qx-2 provides early phase separation and early aggregation, resulting in oversized crystal domains. Consequently, the PM6:Qx-1-based 1 cm 2 flex...

Batch-Reproducible and Thickness-Insensitive Mesopolymer Zwitterion Interlayers for Organic Solar Cells

“…Organic solar cells (OSCs), capable of converting solar power into electric energy, are promising candidates for a broad range of applications owing to their light weight, flexibility, and large-area solution processability. − Researchers have been improving the power conversion efficiencies (PCEs) of OSCs rapidly by materials innovations and device optimization as shown, in particular, in a recent breakthrough on fused-ring electron acceptors (FREAs). − Among these high-performance photovoltaic materials, interlayer materials are crucial for achieving highly efficient OSCs by removing energy barriers between metal electrodes and active layers, affording efficient interfacial charge transport and collection. − Even in the era of fullerene-based solar cells, aliphatic amine-containing polymers (e.g., polyethylenimine (PEIE)) and amine-substituted polyfluorene derivatives (e.g., PFN) were widely used as cathode interlayers (CILs) to improve device performance. However, the thickness of the layers significantly influenced solar cell performance, making them useless in large area coating processes .…”

Film-formation dynamics coordinated by intermediate state engineering enables efficient thickness-insensitive organic solar cells

“…Normally, D:A phase separation is quickly constructed due to the fast evaporation rate of CF solvent after the liquid–solid transition. 38 Strikingly, the intermediate state explored in this work provides a novel approach to modulating the film-formation kinetics and finely constrains the scale of phase separation. Indeed, for the PM6:Y6 control blend, the transition time occurred at 105 ms, whereas the solidification process evolved earlier after the addition of TBr (58 ms) due to the robust intermolecular interaction between TBr and Y6 and further forms pre-aggregations in the blend solution.…”

18.9% Efficiency Ternary Organic Solar Cells Enabled by Isomerization Engineering of Chlorine‐Substitution on Small Molecule Donors

“…Bulk-heterojunction (BHJ) organic solar cells (OSCs) has been recognized as one of most promising photovoltaic technology owing to the advantage of light weight, mechanical flexibility, low cost, and solution processing ability. [1][2][3][4][5][6] Benefiting from the composition of the active layer, ternary OSCs can be classified to either one donor/two acceptor (1D2A) or two donors/ one acceptor (2D1A). [24][25][26][27] Nowadays, ternary OSCs composing two acceptors are more widely studied because of their high miscibility of the two acceptors and easily tuned energy levels.…”

“…Bulk‐heterojunction (BHJ) organic solar cells (OSCs) has been recognized as one of most promising photovoltaic technology owing to the advantage of light weight, mechanical flexibility, low cost, and solution processing ability. [ 1–6 ] Benefiting from the organic material innovation and device optimization engineering, especially the development of small‐molecule (SM) nonfullerene acceptors (NFAs), tremendous progress has been made in recent years for OSCs. [ 7–15 ] When Y‐series NFAs combined with appropriate wide‐bandgap polymer donors such as PM6, the highest PCE of PM6‐based binary OSCs has achieved 18.74%.…”