Interface Engineering for Highly Efficient Organic Solar Cells

Abstract

Organic solar cells (OSCs) have made dramatic advancements during the past decades owing to the innovative material design and device structure optimization, with power conversion efficiencies surpassing 19% and 20% for single‐junction and tandem devices, respectively. Interface engineering, by modifying interface properties between different layers for OSCs, has become a vital part to promote the device efficiency. It is essential to elucidate the intrinsic working mechanism of interface layers, as well as the related physical and chemical processes that manipulate device performance and long‐term stability. In this article, the advances in interface engineering aimed to pursue high‐performance OSCs are reviewed. The specific functions and corresponding design principles of interface layers are summarized first. Then, the anode interface layer, cathode interface layer in single‐junction OSCs, and interconnecting layer of tandem devices are discussed in separate categories, and the interface engineering‐related improvements on device efficiency and stability are analyzed. Finally, the challenges and prospects associated with application of interface engineering are discussed with the emphasis on large‐area, high‐performance, and low‐cost device manufacturing.

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

“…However, the thickness of the layers significantly influenced solar cell performance, making them useless in large area coating processes . Subsequently, amine-functionalized conjugated small molecules or polymers were developed to broaden the thickness processing window of the interlayers, including PNDIT-F3N, PDIN, and PDINN. ,, Recent studies have shown, though, that these amine-containing CILs are basic in nature, so they may react with FREAs by a Michael addition, severely degrading device performance and stability. − …”

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

“…Organic solar cells (OSCs) have drawn a lot of interest as a low-cost renewable energy source with large-scale capabilities on various substrates. − As a result, power conversion efficiencies (PCEs) have significantly improved, which have exceeded 20%. − The advancements were acquired by the discovery of an effective active layer, the modification of photoactive layer morphology, and the enhancement of interface properties …”

Synergistic Plasmonic Responses of Multi-Shaped Au Nanostructures Hybridized with Few-Layer WS2 Nanosheets for Organic Solar Cells

“…Despite numerous attempts in the development of organic solar cells (OSCs) such as synthesis of novel organic semiconducting materials, controlling the photoactive layer morphology, nano-engineering at the interfaces, understanding the detailed photo-physics of devices, etc., their power conversion efficiency (PCE) remains below the Shockley–Queisser limit. − The major hurdle in improving the performance of OSCs is overcoming the issues related to the fundamental tradeoff between ray optic path length and Augur charge-carrier recombination losses. Due to the lower charge-carrier mobility of organic semiconductors, the physical thickness of photoactive layers is needed to maintain as low as possible to minimize the recombination losses, which certainly limits light absorption. − To overcome this issue, researchers have designed an optically thick medium by employing the elevated local density of optical states (LDOS) in physically thin photoactive layers, using many innovative strategies such as diffraction gratings, V-shaped light trapping structures, photonic crystals, and metal nanostructures. ,− Among these methods, incorporating the plasmonic metal nanostructures is a simple and effective way to attain higher LDOS, which can provide absorption enhancement factors several times higher than the Yablonovitch limit. , Upon interaction with incident light, the metal nanostructures induce two radiative plasmonic effects, near-field enhancement, and far-field scattering, which considerably increase the electric field intensity and optical path length inside the active layer, respectively. , These effects crucially depend on the size and the location of metal nanostructures in the devices. The nanostructures of small size (<20 nm) are highly beneficial as subwavelength antennas and are incorporated inside the active layer to mainly utilize the near-field enhancement effect.…”