26.75,cm2,organic,solar,modules,demonstrate,a,certified,efficiency,of,14.34%

Erming Feng ,Yunfei Han ,Jianhui Chang ,Hengyue Li ,Keqing Huang, ,Lixiu Zhang,Qun Luo,Jidong Zhang,Changqi Ma,Yingping Zou,Liming Ding,,and Junliang Yang,

1Hunan Key Laboratory for Super-Microstructure and Ultrafast Process,School of Physics and Electronics,Central South University,Changsha 410083,China

2Printable Electronics Research Center,Suzhou Institute of Nano-Tech and Nano-Bionics,Chinese Academy of Sciences,Suzhou 215123,China

3College of Engineering and Computer Science,Australian National University,Canberra 2600,Australia

4Center for Excellence in Nanoscience,Key Laboratory of Nanosystem and Hierarchical Fabrication (CAS),National Center for Nanoscience and Technology,Beijing 100190,China

5Changchun Institute of Applied Chemistry,Chinese Academy of Sciences,Changchun 130022,China

6College of Chemistry and Chemical Engineering,Central South University,Changsha 410083,China

Organic solar cells (OSCs) have been developed rapidly in past years,due to the fast evolution of wide-bandgap copolymer donors and low-bandgap non-fullerene acceptors[1-9].At present,the highest power conversion efficiencies (PCEs) for single-junction OSCs and tandem OSCs exceed 19% and 20%,respectively[10,11].These OSCs are typically fabricated by using low-boiling-point solvent chloroform (CF) with an effective area ＜0.1 cm2.The doctor-blading deposition is the most advantageous technique to fabricate OSCs with low-boilingpoint solvent for upscaling lab cells to industrial-scale modules[12],exhibiting simple operation,low cost,and high material utilization[13-15].Herein,a typical OSC material system PM6:Y6 (Fig.1(a)) was used to fabricate OSCs modulesviadoctor-blading deposition in ambient condition,and the influence of the ambient temperature and substrate temperature on the film quality was investigated.Furthermore,PC61BM was incorporated into PM6:Y6 blend,and a certified record efficiency of 14.34% was achieved for OSC modules with a designated illumination area of 26.75 cm2.

Some works indicated that the performance parameters for doctor-bladed OSCs from low-boiling-point solvent CF were normally dependent on the temperatures (25—45 °C)[12,16-18].However,controlling the ambient temperature and substrate temperature at the same value,for example,from 17 to 30 °C,interesting results were achieved,i.e.,doctor-bladed film quality and device performance are almost independent on temperature.Atomic force microscopy(AFM) images of doctor-bladed PM6:Y6 films at different temperatures (17,24 and 30 °C) are almost the same (Fig.S1).Meanwhile,the root-mean-square roughnesses (Rrms) are around 1.50 nm.In addition,grazing incidence wide-angle Xray scattering (GIWAXS) patterns for doctor-bladed PM6:Y6 thin films at different temperatures also exhibit the similar line-cut profiles (Fig.1(b) and Fig.S2).The (010) peaks at 1.73 Å—1in the out-of-plane (OOP) direction and the (100)peaks at 0.29 Å—1in the in-plane (IP) direction indicate the coexistence of face-on and edge-on orientation in three cases.The diffraction peaks of PM6:Y6 films locate at the sameqvalues,indicating the same lamellar stacking distance and π—π stacking distance.

Doctor-bladed cells at three temperatures were fabricated with a structure of ITO/ZnO:PEI/PM6:Y6/MoO3/Ag[19-21].The current density—voltage (J—V) curves and external quantum efficiency (EQE) spectra are shown in Figs.1(c) and 1(d),and the performance data are listed in Table S1.The cells processed at 17,24 and 30 °C exhibit PCEs of 14.57%,14.78% and 14.64%,respectively,and the average PCEs are 14.35%,14.58% and 14.46%,respectively.The results suggest that the performance parameters for three cases are almost the same,which are consistent with the results of morphology and GIWAXS.The dependence ofJ—Vcharacteristics on light intensity (Plight) was used to investigate the recombination kinetics in cells.As shown in Fig.S3(a),three cells show an almost equalαvalue of 0.975,indicating that the bimolecular recombination is not remarkable in PM6:Y6 cells made at three temperatures.TheVocas a function ofPlightis plotted in Fig.S3(b).When the slope ofVocversus ln(Plight) is equal to 1 or 2kT/q,the dominant recombination mechanism is bimolecular recombination or Shockley-Real-Hall recombination,respectively.The calculated slopes for the devices at 17,24 and 30 °C are 1.398,1.387 and 1.414kT/q,respectively.The results indicate that PM6:Y6 cells processed at three temperatures have relatively strong trap-assisted recombination,instead of bimolecular recombination.

Furthermore,doctor-bladed large-area OSC modules were made at 24 °C in ambient condition.TheJ—Vcurves of the modules with a designated illumination area of 26.75 cm2are shown Fig.1(e),and the photovoltaic parameters are listed in Table 1.The modules gave a PCE of 13.71%,with aVocof 10.73 V,aJscof 1.792 mA/cm2,and an FF of 71.29%.The certified PCE is 13.56% by the Chinese National PV Industry Measurement and Testing Center (NPVM) (Figs.S4—S10).Using fullerene derivatives is a simple and effective way to enhance PCE[22-24].Thus,it is possible to further improve the module efficiencyviaintroducing PC61BM into PM6:Y6 blend.The modules based on PM6:Y6:PC61BM (1 : 1 : 0.2) offer a record PCE of 14.35%,with aVocof 10.89 V,aJscof 1.814 mA/cm2,and an FF of 73.42% (Table 1).NPVM demonstrates a PCE of 14.34% (Figs.S11—S17).This certified PCE is the highest value reported to date for large-area OSC modules.

Fig.1.(Color online) (a) Chemical structures of PM6 and Y6.(b) 1D GIWAXS line curves along the out-of-plane (OOP,dotted line) and in-plane (IP,solid line) directions.(c) J—V curves for PM6:Y6 cells made at different temperatures.(d) EQE spectra for PM6:Y6 cells made at different temperatures.(e) J—V curves for PM6:Y6 and PM6:Y6:PC61BM modules with a designated illumination area of 26.75 cm2.

Table 1. Performance data for doctor-bladed modules with a designated illumination area of 26.75 cm2.

In short,we found that the morphology and device performance for doctor-bladed PM6:Y6 thin films from low-boiling-point solvent are almost independent on the temperatures if controlling the ambient temperature and substrate temperature at the same value.With a designated illumination area of 26.75 cm2,the large-area PM6:Y6 modules demonstrate a certified PCE of 13.56%,and the PM6:Y6:PC61BM modules demonstrate a certified record PCE of 14.34%.

Acknowledgements

This work was supported by the National Key Research and Development Program of China (2017YFA0206600),the National Natural Science Foundation of China (52173192),the Science and Technology Innovation Program of Hunan Province (2020RC4004),and the Special Funding for the Construction of Innovative Provinces in Hunan Province(2020GK2024).L.Ding thanks the open research fund of Songshan Lake Materials Laboratory (2021SLABFK02) and the National Natural Science Foundation of China (51922032,21961160720).The authors also thank Vacuum Interconnected Nanotech Workstation,Suzhou Institute of Nano-Tech and Nano-Bionics (CAS).

Appendix A.Supplementary materials

Supplementary materials to this article can be found online at https://doi.org/10.1088/1674-4926/43/10/100501.