Towards High Performance Organic Photovoltaic Cells: A Review of Recent Development in Organic Photovoltaics

Abstract

Organic photovoltaic cells (OPVs) have been a hot topic for research during the last decade due to their promising application in relieving energy pressure and environmental problems caused by the increasing combustion of fossil fuels. Much effort has been made toward understanding the photovoltaic mechanism, including evolving chemical structural motifs and designing device structures, leading to a remarkable enhancement of the power conversion efficiency of OPVs from 3% to over 15%. In this brief review, the advanced progress and the state-of-the-art performance of OPVs in very recent years are summarized. Based on several of the latest developed approaches to accurately detect the separation of electron-hole pairs in the femtosecond regime, the theoretical interpretation to exploit the comprehensive mechanistic picture of energy harvesting and charge carrier generation are discussed, especially for OPVs with bulk and multiple heterojunctions. Subsequently, the novel structural designs of the device architecture of OPVs embracing external geometry modification and intrinsic structure decoration are presented. Additionally, some approaches to further increase the efficiency of OPVs are described, including thermotics and dynamics modification methods. Finally, this review highlights the challenges and prospects with the aim of providing a better understanding towards highly efficient OPVs.

Star-shaped D–π–A oligothiophenes with a tris(2-methoxyphenyl)amine core and alkyldicyanovinyl groups: synthesis and physical and photovoltaic properties

“…Synthesis of star-shaped oligomers with m-TPA and alkyl-DCV groups, N(Ph-OMe-2T-DCV) 3 , N(Ph-OMe-2T-DCV-Me) 3 , 35 N(Ph-OMe-3T-DCV-Et) 3 , and N(Ph-OMe-3T-DCV-Hex) 3 , was carried out using our recently developed approach for their analogs with the TPA core. 15,16 The synthetic routes outlined in Scheme 2 include several key reaction stages: preparation of the initial aldehyde or ketones (Schemes 2a and b), synthesis of an organoboron derivative of bi-or terthiophene precursors (Scheme 2c), and preparation of star-shaped precursors with protective groups followed by the deprotection reaction and substitution of carbonyl functions by DCV groups (Scheme 2d).…”

“…Second, protection of carbonyl functions of the ketones was found to be more convenient with 5,5-dimethyl-1,3-dioxane groups as compared to previously used 1,3-dioxolane ones, due to higher stability and better isolated yields of the protected compounds. Note that for the synthesis of the model star-shaped molecule with DCV groups, N(Ph-OMe-2T-DCV) 3 , we have used for the first time a similar strategy as employed for the molecules with alkyl-DCV groups, whereas their common preparation is based on Vilsmeier-Haack formylation of star-shaped oligothiophenes followed by Knöevenagel condensation. 12,16 The main difference in the synthetic route for N(Ph-OMe-2T-DCV) 3 , as compared to the molecules with alkyl-DCV groups, is preparation of the aldehyde precursor (1a) instead of the ketone one, which was done by lithiation of commercially available 2,2 0 -bithiophene followed by its reaction with dimethylformamide (DMF) in 94% yield.…”

“…[1][2][3] Despite the fact that conjugated polymers are dominating the field of bulk heterojunction (BHJ) organic solar cells (OSCs), 4 small molecules are receiving increasing attention due to their well-defined molecular structures, ease of functionalization, amenability to standard organic purification and characterization methods, and reduced batch-to-batch variability. Recently, there has been significant progress in the development of small molecules for use in BHJ OSCs.…”

Modifications of ZnO Interlayer to Improve the Power Conversion Efficiency of Organic Photovoltaic Cells

“…Yu et al [23] have studied the influence of device structures on power conversion efficiency, among other factors.…”

Optimization of Cu2ZnSnS4 Absorber Layers via Sulfurization of Electrodeposited Cu-Zn-Sn Precursors for Photovoltaic Applications

“…New generation PV devices made of materials containing earth-abundant elements include perovskites, polymers, quantum dots, and CZTS based solar cells [14][15][16][17][18][19][20]. For each of these, material complexity and manufacturing methods are bottlenecks towards the implementation of efficient earth-abundant based PVs.…”