Cathode Interlayer Based on Naphthalene Diimide: A Modification Strategy for Zinc-Oxide-Free Inverted Organic Solar Cells

Abstract

Perylene diimide with ammonium oxide as a terminal group (named PDIN-O) is a well-known cathode interlayer in conventional-type organic solar cells (OSCs). Since naphthalene diimide exhibits a lower LUMO level than perylene diimide, we chose it as a core to further control the LUMO level of the materials. Small molecules (SMs) produce a beneficial interfacial dipole by the end of ionic functionality at the side chain of naphthalene diimide. With the active layer based on a nonfullerene acceptor (PM6:Y6BO), the power conversion efficiency (PCE) is enhanced by utilizing SMs as cathode interlayers. We discovered that the inverted-type OSC with naphthalene diimide with oxide as a counteranion (NDIN-O) shows poor thermal stability, which can cause irreversible damage to the interlayer−cathode contact, leading to poor PCE (11.1%). To overcome the disadvantage, we introduce NDIN-Br and NDIN-I with a higher decomposition temperature. An excellent PCE of 14.6% was achieved with the device based on NDIN-Br as an interlayer, which is almost the same as the PCE of the ZnO-based device (15.0%). The device based on NDIN-I without the ZnO layer exhibits an improved PCE of 15.4%, which is slightly higher than the ZnO-based device. The result offers a replacement of the ZnO interlayer, which is necessary to carefully manage the sol−gel transition by annealing temperatures as high as 200 °C and leading to low-cost manufacture of OSCs.

Brominated Quaternary Ammonium Salt-Assisted Hybrid Electron Transport Layer for High-Performance Conventional Organic Solar Cells

“…HB contains a hexane alkyl chain sandwiched between two electropositive quaternary ammonium and electronegative bromine (Br) pairs. With the strong polarity of ammonium and Br, HB shows a large dipole moment of 10.9 D from amine to Br (Figure c), which might be helpful in forming interfacial dipoles in the device and assisting charge collection. , Additionally, HB possesses a high transmittance from 300 to 900 nm. When HB was dissolved in methanol (MeOH) and cast on a PM6:C5-16 photoactive layer, negligible difference was observed in the absorption spectrum of PM6:C5-16 (Figure d), implying that HB did not alter the morphology of the photoactive layer.…”

Novel Polyelectrolytes Based on Naphthalene Diimide with Different Counteranions for Cathode Interlayers in Polymer Solar Cells

“…The values of the align closely with the values. Lower values were observed when PF-NDIN-I-OH was applied in the device, suggesting a potential for leakage current in the device with PF-NDIN-I-OH as the interlayer [ 27 ]. Even though the device with PF-NDIN-I-OH has the lowest values, the device exhibits the best , which mostly contributes to PCE enhancement.…”

“…The ionic charges offer polyelectrolytes a straightforward process for a action between molecules and fine-tuning the optical properties [25]. Ad interface properties can be finely tuned by different types of counteranio search has demonstrated that the WF of electrodes and ZnO can be modifi the counteranion [5,[26][27][28]. Polyelectrolytes with various CAs have been u imize the collection of charge capability at the cathode interface [29].…”

“…Additionally, the interface properties can be finely tuned by different types of counteranions (CAs). Research has demonstrated that the WF of electrodes and ZnO can be modified by varying the counteranion [ 5 , 26 , 27 , 28 ]. Polyelectrolytes with various CAs have been utilized to maximize the collection of charge capability at the cathode interface [ 29 ].…”

High-efficiency ultrathin flexible organic solar cells with a bilayer hole transport layer

“…1–8 In recent years, with the rapid development of active layer materials and interface engineering, the power conversion efficiency (PCE) of single-junction organic solar cells has surpassed 19%. 9–22 However, the lightweight and flexible characteristics of organic solar cells will not be reflected in rigid devices. 23–30 The fabrication of organic solar cells on ultrathin substrates (typically <10 μm in thickness), distinguished by excellent mechanical flexibility and conformable attachment, presents promising applications in the realm of wearable devices.…”