Molecular design of interfacial layers based on conjugated polythiophenes for polymer and hybrid solar cells

Abstract

In the past two decades, bulk heterojunction organic photovoltaic (OPV) devices have emerged as attractive candidates for solar energy conversion due to their lightweight design and potential for low‐cost, high‐throughput, solution‐phase processability. Interfacial engineering is a proven efficient approach to achieve OPV devices with high power conversion efficiencies. This mini‐review provides an overview of the key structural considerations necessary when undertaking the molecular design of conjugated polyelectrolytes, for application as interfacial layers (ILs). The different roles of ILs are outlined, together with the advantages and disadvantages of competing classes of IL materials. Particular emphasis is placed on the design and synthesis of water‐soluble polythiophene‐based IL materials and the influence of their structural characteristics on their performance as a promising class of IL material. Finally, the challenges and opportunities for polythiophenes as IL materials for OPV devices and other solution‐processed solar cell technologies (e.g. perovskite solar cells) are discussed. © 2017 Society of Chemical Industry

Conjugated ionic (co)polythiophene-based cathode interlayers for bulk heterojunction organic solar cells

“…[4][5][6][7][8] Even though most research activities have been oriented on the development of novel active layer materials with appropriate optoelectronic properties, the introduction of interlayer materials has become a widely accepted approach to further enhance the device efficiency. [9][10][11][12][13][14][15][16][17] One class of interlayer materials of particular interest are conjugated polyelectrolytes (CPEs). They can be processed from eco-friendly, orthogonal solvents, thereby preventing re-dissolution of the underlying layer during device fabrication.…”

“…The conjugated polymer backbone has not been explored much further than polyfluorene and polythiophene derivatives and most variation has been introduced in the ionic moieties. 12 Previous work in our group focused on imidazolium-functionalized polythiophenes, outperforming the ammonium-functionalized counterparts. 11 More recently, impedance spectroscopy measurements revealed that the dielectric permittivity, induced by the ionic functionalities, is an important parameter to improve charge collection.…”

Theoretical evaluation of chemical substitutions along the main chain of poly(3‐hexylthienylene‐vinylene) for solar cell applications

“…In all, 143 new P3HTV derivatives were obtained. We choose to substitute at position 4 of the thiophene ring because there have already been reports in the literature of substitutions at this position for similar materials, such as P3HT , , , . As regards the vinyl group, only one chemical substitution was performed in the position highlighted in Fig.…”

“…We choose to substitute at position 4 of the thiophene ring because there have already been reports in the literature of substitutions at this position for similar materials, such as P3HT. 9,13,14,21 As regards the vinyl group, only one chemical substitution was performed in the position highlighted in Fig. 1 because there are works in the literature that indicate that replacing the two hydrogens of the vinyl group causes a considerable worsening in the morphology of the material without significant gains in electronic structure.…”

“…To improve the efficiency of BHJ OSCs, one of the options is to study/produce new organic materials for application in the active layer that have better intrinsic properties than those that are already used. 2,[7][8][9][10] Current works have focused on the search for new electron donor polymers, 11,12 since the derivatives of fullerenes used as electron acceptors are already well established in this area. 3 The use of chemical substitutions in existing organic materials has been a very useful tool when it is desired to modify electronic properties.…”