Understanding Solvent Manipulation of Morphology in Bulk‐Heterojunction Organic Solar Cells

Abstract

Film morphology greatly influences the performance of bulk-heterojunction (BHJ)-structure-based solar cells. It is known that an interpenetrating bicontinuous network with nanoscale-separated donor and acceptor phases for charge transfer, an ordered molecular packing for exciton diffusion and charge transport, and a vertical compositionally graded structure for charge collection are prerequisites for achieving highly efficient BHJ organic solar cells (OSCs). Therefore, control of the morphology to obtain an ideal structure is a key problem. For this solution-processing BHJ system, the solvent participates fully in film processing. Its involvement is critical in modifying the nanostructure of BHJ films. In this review, we discuss the effects of solvent-related methods on the morphology of BHJ films, including selection of the casting solvent, solvent mixture, solvent vapor annealing, and solvent soaking. On the basis of a discussion on interaction strength and time between solvent and active materials, we believe that the solvent-morphology-performance relationship will be clearer and that solvent selection as a means to manipulate the morphology of BHJ films will be more rational.

A new quinoxaline and isoindigo based polymer as donor material for solar cells: Role of ecofriendly processing solvents on the device efficiency and stability

“…Interestingly, the achievement of the best compromise between light harvesting (thickness), generated current, morphology and charge transport/collection for o ‐xylene processed blends represents an important aspect that highlights the key role of the processing solvent on the self‐assembly of the D:A blend . Indeed, the possibility to have a slightly thicker and more efficient P1:PC 61 BM blend using o ‐xylene as a processing solvent, is likely the result of a fine and ideal polymer entanglement and/or backbone orientation during the drying process.…”

Recent Progress in Fused-Ring Based Nonfullerene Acceptors for Polymer Solar Cells

“…The PCE of PSC is proportional to open-circuit voltage ( V oc ), short-circuit current density ( J sc ), and fill factor (FF). The progress of PSCs is closely related to the innovation of photoactive materials (donor and acceptor materials) (He and Li, 2011 ; Li, 2013 ; Cui et al, 2014 , 2016 ; Ye et al, 2014 ; Lu et al, 2015 ; Cui and Wong, 2016 ; Cui Y. et al, 2017 ; Hu et al, 2017 ; Lopez et al, 2017 ; Osaka and Takimiya, 2017 ; Zou et al, 2017 ; Gupta et al, 2018 ; Liu et al, 2018 ; Sun et al, 2018 ), interface engineering (He et al, 2012 ; Duan et al, 2013 ; Chueh et al, 2015 ; Wang et al, 2015 ; Chen et al, 2016 ; Street, 2016 ), and device optimization (Ameri et al, 2009 , 2013 ; Meillaud et al, 2015 ; Zhao et al, 2018 ). Especially, the development of PSCs is always accompanied by photoactive material innovations.…”

Semiconducting end-perfluorinated P3HT–fullerenic hybrids as potential additives for P3HT/IC70BA blends

“…The performance of such devices can be further improved by the stabilization and control over the morphology of the P3HT:fullerene active blends. This can be achieved through several approaches: (1) functionalisation of either the electron donor or electron acceptor with different functional groups to affect the miscibility and thus co-crystallization in the blend; 25,26,27,28 (2) employing various thermal or solvent annealing steps which both improve the nanophase separation, 11,29,30 25,31,32,33,34,35 or (4) non-covalent interactions between compatibilisers bearing nitrogen heterocycles (such as pyridine-units) and the fullerene acceptor of the active blend. 36,37,38 Incorporation of small amounts (1-20 wt %) of such compatibilisers in the polymer:fullerene blend affects the morphology of the final blend and enhances phase stability between the major components.…”