Effect of a Long Alkyl Group on Cyclopentadithiophene as a Conjugated Bridge for D-A-π-A Organic Sensitizers: IPCE, Electron Diffusion Length, and Charge Recombination

被引:73
作者
Chai, Qipeng [1 ,2 ]
Li, Wenqin [1 ,2 ,3 ]
Wu, Yongzhen [1 ,2 ]
Pei, Kai [1 ,2 ]
Liu, Jingchuan [1 ,2 ]
Geng, Zhiyuan [4 ]
Tian, He [1 ,2 ]
Zhu, Weihong [1 ,2 ]
机构
[1] E China Univ Sci & Technol, Shanghai Key Lab Funct Mat Chem, Key Lab Adv Mat, Shanghai 200237, Peoples R China
[2] E China Univ Sci & Technol, Inst Fine Chem, Shanghai 200237, Peoples R China
[3] Shanghai Second Polytech Univ, Sch Urban Dev & Environm Engn, Shanghai 201209, Peoples R China
[4] Northwest Normal Univ, Gansu Key Lab Polymer Mat, Coll Chem & Chem Engn, Key Lab Ecoenvironm Related Polymer Mat,Minist Ed, Lanzhou 730070, Gansu, Peoples R China
关键词
solar cells; organic sensitizers; conjugation bridge; alkyl group; electron diffusion length; photovoltaic efficiency; OPEN-CIRCUIT VOLTAGE; SOLAR-CELLS; CONVERSION-EFFICIENCY; ENERGY-LEVELS; SIGNIFICANT ENHANCEMENT; RUTHENIUM SENSITIZERS; TIO2; FILM; DYES; MOIETY; PERFORMANCE;
D O I
10.1021/am503891q
中图分类号
TB3 [工程材料学];
学科分类号
0805 ; 080502 ;
摘要
The option of using conjugated pi-linkers is critical for rational molecular design toward an energy-level strategy for organic sensitizers. To further optimize photovoltaic performance, methyl- and octyl-substituted 4H-cyclopenta[2,1-b:3,4-b']dithiophene ( CPDT) are introduced into D-A-pi-A featured sensitizers. Along with CPDT, instead of thiophene as conjugated bridge, WS-39 and WS-43 exhibit an extended spectral response due to the excellent conjugation and coplanarity of CPDT. Specifically, we focused on the critical effect of length of the alkyl group linked to the bridging carbon atoms of CPDT on the photovoltaic performances. Octyl-substituted WS-39 shows a broader IPCE onset with an enhanced photovoltage relative to the analogue WS-5. In contrast, WS-43, with methyl substituted on the CPDT moiety, presents a relatively low quantum conversion efficiency within the whole spectral response region, along with low photocurrent density. WS-43 displays a distinctly low IPCE platform, predominately arising from the short electron diffusion length with significant electron loss during the electron transport. The relative movement of the conduction band edge (E-CB) and charge transfer resistance as well as lifetime of injected electrons are studied in detail. Under standard AM 1.5 conditions, WS-39-based solar cells show a promising photovoltaic efficiency of 9.07% (J(SC) = 16.61 mA cm(-2), V-OC = 770 mV, FF = 0.71). The octyl chains attached on CPDT can provide dual protection and exhibit a high propensity to prevent binding of the iodide triiodide redox couple, producing an efficient shielding effect to retard the charge recombination and resulting in improvement of V-OC. Our research paves the way to explore more efficient sensitizers through ingenious molecular engineering.
引用
收藏
页码:14621 / 14630
页数:10
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