An Alcohol‐Soluble N‐Annulated Perylene Diimide Cathode Interlayer for Air‐Processed, Slot‐Die Coated Organic Photovoltaic Devices and Large‐Area Modules

Abstract

Cathode interlayers (CILs) in organic photovoltaics (OPVs) are actively being researched as they are critical for device stability and performance. Herein, N‐annulated perylene diimide with a 2‐ethyl‐hexyl side chain (PDIN‐EH) is demonstrated, which is facile to synthesize as compared with conventional CILs such as PFN‐Br, exhibits solubility, and subsequent processability from ethanol. The PDIN‐EH is evaluated as a CIL in an air‐processed, slot‐die coated OPV consisting of PEDOT:PSS as the hole transport layer, PM6:Y6C12 as the bulk heterojunction, and top silver cathode electrode. All the organic layers are slot‐die coated from green solvents and devices achieve a power convention efficiency of more than 12%, a result that is among the best reported under ambient conditions for printed OPVs. Microscopy images reveal that the PDIN‐EH affords smooth film formation when slot‐die coated on top of PM6:Y6C12 bulk heterojunction for an improved contact with the Ag electrode. Furthermore, the fabrication of large‐area OPV modules on glass and flexible (polyethylene terephthalate) substrates is successfully demonstrated, with five cells connected in series achieving efficiency over 7% and open‐circuit voltage over 3.5 V. Herein, useful guidelines for achieving fully printed organic electronic devices from green solvents at a potential industrial scale are provided.

Systematic Investigation of Core and Endcap Selection on the Development of Functional π-Conjugated Materials

“…OPVs are considered a leading alternative energy source candidate, whereby abundant solar energy that irradiates the bulk heterojunction (BHJ) photoactive layer facilitates photon harvesting and exciton splitting to generate electricity. ,, The development of advanced π-conjugated materials has swiftly overtaken conventional fullerenes because the synthetic versatility of π-conjugated materials allows for better optical and energetic matching with electron donor polymer(s) in the photoactive layer. , In fact, recent reports have even shown that pairing highly fused A–D–A systems (i.e., Y6) with appropriate donor polymer materials (i.e., PM6) can lead to power conversion efficiencies (PCEs) exceeding 18%. − However, limitations in the PM6:Y6-based OPV device size and air stability have prompted our group (and many others) to fabricate large-scale, roll-to-roll solution-processable OPV devices. Although the use of ambient conditions lowered the overall PCE of these PM6:Y6-based devices, we have found the integration of NPDI-derived materials as the CIL can significantly improve the overall OPV device PCE and stability. − …”

“…In this preliminary CIL thickness-dependence experiment, it was observed that CIL thin films <10 nm gave the best OPV device performance and that OPV device PCE significantly dropped if the CIL thin film thickness exceeded 15 nm. These results suggest that while molecule A can effectively modify the energy levels of the PM6:Y6/Ag interface in such a way that charge carrier mobility is improved, molecule A can also act as a barrier to charge transport and collection if the CIL thin film is too thick. , Since we expect similar thickness-dependence behavior for CIL molecules B–D , all OPV devices were processed using 0.5 mg mL –1 solutions of A–D in EtOAC.…”

“…These results suggest that while molecule A can effectively modify the energy levels of the PM6:Y6/Ag interface in such a way that charge carrier mobility is improved, molecule A can also act as a barrier to charge transport and collection if the CIL thin film is too thick. 53,58 Since we expect similar thickness-dependence behavior for CIL molecules B−D, all OPV devices were processed using 0.5 mg mL −1 solutions of A−D in EtOAC.…”

A dπ‐pπ Conjugated System with High Mobility and Strong Emission Simultaneously

“…It is worth noting that in order to prepare PDI derivatives with certain solubility in alcohols, to meet the processing needs of interface layers in OSCs, the skeleton of PDI usually needs to be modified with amino, amino-N-oxide, or aliphatic amine groups. [39][40][41] In this case, the PDI-based carbolong complexes 1a-1c and 2a-2b are soluble in alcohols, and they were chosen as the ETL materials in OSCs to evaluate their photovoltaic performances. The devices are fabricated with the architecture of ITO/PEDOT:PSS/ PM6:Y6/ETL (1 mg mL −1 )/Ag (see Supporting Information for details).…”

Ternary organic solar cells with a selenophene-containing donor guest achieve a high efficiency of 18.41%

“…With the constant development of photoactive materials and device engineering, in recent years, bulk heterojunction (BHJ) organic solar cells (OSCs) have made significant achievements. [1][2][3][4][5][6][7][8][9][10][11][12] Power conversion efficiencies (PCEs) of over 19% have been achieved for both single junction and tandem OSCs. [13][14][15][16][17][18][19][20][21][22] Combining the unique advantages of light weight, large-area fabrication, and flexibility, BHJ-OSCs show great commercialization prospects.…”