High Performance Roll‐to‐Roll Produced Fullerene‐Free Organic Photovoltaic Devices via Temperature‐Controlled Slot Die Coating

Abstract

Solution‐processed organic photovoltaics (OPVs) have continued to show their potential as a low‐cost power generation technology; however, there has been a significant gap between device efficiencies fabricated with lab‐scale techniques—i.e., spin coating—and scalable deposition methods. Herein, temperature‐controlled slot die deposition is developed for the photoactive layer of OPVs. The influence of solution and substrate temperatures on photoactive films and their effects on power conversion efficiency (PCE) in slot die coated OPVs using a 3D printer‐based slot die coater are studied on the basis of device performance, molecular structure, film morphology, and carrier transport behavior. These studies clearly demonstrate that both substrate and solution temperatures during slot die coating can influence device performance, and the combination of hot substrate (120 °C) and hot solution (90 °C) conditions result in mechanically robust films with PCE values up to 10.0% using this scalable deposition method in air. The efficiency is close to that of state‐of‐the‐art devices fabricated by spin coating. The deposition condition is translated to roll‐to‐roll processing without further modification and results in flexible OPVs with PCE values above 7%. The results underscore the promising potential of temperature‐controlled slot die coating for roll‐to‐roll manufacturing of high performance OPVs.

Slot‐Die and Roll‐to‐Roll Processed Single Junction Organic Photovoltaic Cells with the Highest Efficiency

“…[31][32][33][34][35] For example, Yan and co-workers showed that blade-coated PSCs with PffBT4T-2OD:PC 71 BM based BHJ can produce a high PCE of up to 9.9%. [37][38][39] However, the slot-die method has not been well studied and the efficiency of slot-die based devices has still remained low, compared to the high PSCs in the recent reported spin-coating based PSCs. [31] In particular, 12.88% PCE was achieved in doctor blade-coated PBDB-TF:IT-4F PSCs through controlling the surface morphology of the ZnO interlayer; [36] and more recently, Hou and co-workers demonstrated a top efficiency of 13.1% from the blade-coated PSCs based on T1:IT-4F.…”

“…[35] Hou and coworkers also presented the excellent PCE of 9.5% in doctor blade-coated PSCs based on PTB7-Th and 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′] dithiophene) (ITIC) NFA. [39,40] Furthermore, the PCEs of roll-to-roll slot-die PSCs have been only within ≈(5-7)% [39][40][41] and the 7.32% PCE has been known as the top record efficiency of the roll-to-roll processed PSC. [21] Although the abovementioned studies showed promising results, the blade coating method could have limited practicality in manufacturing, especially for roll-to-roll production, due to the method having difficulty in controlling film-thickness and fabricating stripe patterns; and in fact, there has been no report on the roll-to-roll fabrication of blade-coated PSCs.…”

“…More importantly, the slot-die deposition condition developed by the batch process was translated to roll-to-roll processing equipment and resulted in roll-to-roll processed flexible PSCs with a PCE of 9.57%, which is the highest PCE to date. [39,50] Figure 1c and Figure S1 in the Supporting Information show a schematic of the slot-die coating process and photographic images of the 3D-printer based slot-die coater, respectively. Figure 1a shows the molecular structures of the one electron donor (PTB7-Th) and two electron acceptors (PC 71 BM and COi8DFIC) used in this study.…”

“…Furthermore, the GIWAXS image of the blended film with DIO/Annealing reveals that the DIO additive and thermal Adv. In addition, compared with the DIO-based films with 1.34 nm RMS, the printed films processed with both DIO and thermal annealing conditions resulted in a rougher RMS surface (1.46 nm) that possessed more distinct phase-separation and surface-corrugation for superior carrier-transport/collection and better FF and J sc , [39,66] which could result from the crystallinity improvement in the solid films slot-die processed under the DIO/Annealing conditions. 2019, 9,1901805 annealing treatment clearly improves the face-on orientation.…”

“…We found a higher PCE only in a proceeding report that describes a 9.5% module, without disclosing details of the materials and processing parameters. [39,40,42] More importantly, the performance is still impressive, and the loss in the transition from the batch on glass to continuous roll-to-roll process on flexible substrate was minimal. The inset of Figure 5b shows the flexible PSCs and the roll-to-roll deposition system used for this demonstration.…”