From Straw to Device Interface: Carboxymethyl‐Cellulose‐Based Modified Interlayer for Enhanced Power Conversion Efficiency of Organic Solar Cells

Abstract

The research on organic solar cells (OSCs) has made an immense progress over the last one decade because OSCs possess multiple advantages, such as light-weight, efficient, economical and large-area fabrication. [1][2][3] To date, the power conversion efficiency (PCE) at the laboratory scale has reached up to ≈16% by employing novel interfacial and photoactive materials. [4] Prior to the importance of photoactive layer, interfacial layer also plays a vital role to fabricate high-performance OSC by reducing the energy barrier at the interface and improving charge transfer. [5,6] However, it is usually impossible for the conventional single interlayer materials to satisfy all the requirements. In this regard, it is highly desirable to develop novel interfacial materials with suitable modification for highly efficient OSCs.To develop effective cathode interfacial materials, interface barrier should be minimized with improved electron mobility. Generally, interface barrier originates directly from the mismatch of the energy levels between the active layer and electrodes. Therefore, the key is to design suitable interfacial materials which can significantly reduce the interface barrier between the electrodes and active layer. In the past decades, numerous attempts have been made and significant progresses have been achieved for the cathode interface modification of OSCs. For example, few metallic salts, including LiF, CsF, and Cs 2 CO 3 , [7][8][9] have been integrated into OSCs to modify the interface and the devices exhibited enhanced efficiencies. However, the electron transfer ability of these metallic salts is low and these layers are thickness sensitive (<1 nm), which restrict their application on large scale. In this regard, some organic materials are also introduced for the interface modification of OSCs. Generally, organic materials are synthesized easily with high electron mobility and tunable bandgap energy. Some of them (poly [(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctyfluorene)], polyethylenimine, and polyethylenimine ethoxylated (PEIE)) were found to be effective interface modifiers with matched performance of these devices, compared to the devices using conventional interlayer materials (Ca/Mg). [10,11] However, OSC devices. However, the limited resources, high-cost, and non-ecofriendly nature of petrochemical-based interface materials restrict their commercial applications. Here, a facile and effective approach to prepare cellulose and its derivatives as a cathode interface layer for OSCs with enhanced performance from rice straw of agroforestry residues is demonstrated. By employing this carboxymethyl cellulose sodium (CMC) into OSCs, a highly efficient inverted OSC is constructed, and a power conversion efficiency (PCE) of 12.01% is realized using poly[(2,6-(4,8-bis(5-(2-ethylhexyl)-thiophen-2-yl)-benzo[1,2-b:4,5-b′] dithiophene))-alt-(5,5-(1′,3′-di-2thienyl-5′,7-bis(2-ethylhexyl)benzo[1′,2′-c: 4′,5′-c′]dithiophene-4,8-dione): 3,9-bis(2-methylene -((3-(1, 1-dicyanomethylen...

A Universal Method to Enhance Flexibility and Stability of Organic Solar Cells by Constructing Insulating Matrices in Active Layers

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Flexible and conductive cellulose substrate by layered growth of silver nanowires and indium-doped tin oxide

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