关键词: 三元聚合物电池/
PTB7-Th/
激子解离
English Abstract
Mechanism of ternary polymer solar cells based on P3HT: PTB7-Th: PCBM
Deng Li-Juan,Zhao Su-Ling,
Xu Zheng,
Zhao Ling,
Wang Lin
1.Key Laboratory of Luminescence and Optical Information, Ministry of Education, Beijing Jiaotong University, Beijing 100044, China;
2.Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044, China
Fund Project:Project supported by the National High Technology Research and Development Program of China (Grant No. 2013AA032205), the National Natural Science Foundation of China (Grant Nos. 61575019, 51272022, 11474018), the Research Fund for the Doctoral Program of Higher Education, China (Grant Nos. 20120009130005, 20130009130001), and the Fundamental Research Funds for the Central Universities, China (Grant No. 2012JBZ001).Received Date:19 November 2015
Accepted Date:17 January 2016
Published Online:05 April 2016
Abstract:Recently, ternary bulk-heterojunction (BHJ) polymer solar cells (PSCs) occur as an attractive strategy with simple fabrication technology to extend the spectrum of wide bandgap polymers into the near infrared region by adding a narrow bandgap sensitizer. In this paper, a series of cells including binary BHJ-PSCs with P3HT:PCBM as the active layer (control cell) and ternary BHJ-PSCs with different PTB7-Th doping concentrations are fabricated to investigate the effect of PTB7-Th on the performance of PSC. The short-circuit current density (Jsc) and fill factor (FF) of the ternary PSCs are simultaneously improved by adding a small amount of PTB7-Th into P3HT:PCBM. The champion photoelectric conversion efficient of ternary PSCs (with 15 wt% PTB7-Th) is 3.71%, which is larger than 2.71% of the control cell. In a ternary device, the absorption region shows a distinct red-shift and the relative absorption intensity from 650 nm to 800 nm is gradually enhanced with the incrtease of PTB7-Th doping concentration. The increased photon harvesting in the solar spectral range results in an increased short-circuit current density. However, despite the fact that the photoluminescence (PL) spectrum of P3HT has a large overlap with the absorption spectra of PTB7-Th, which makes it possible for Frster resonance energy to transfer between P3HT and PTB7-Th, the PL intensity of P3HT at 650 nm is quenched with the increase of PTB7-Th doping concentration while the photoluminescence remains almost the same in the long wavelength region, which suggests that the main mechanism between PTB7-Th and P3HT is photo-induced electron transfer from P3HT to PTB7-Th (hole transfer from PTB7-Th to P3HT), not energy transfer. The PSCs with P3HT:PTB7-Th (1:1) as an active layer display a large Jsc compared with the P3HT-based one. When the concentration of PTB7-Th decreases and the concentration of P3HT is unchanged (P3HT:PTB7-Th 1 : 0.5), the Jsc can be further enhanced. The increased Jsc value of P3HT: PTB7-Th (1:0.5) PSCs confirms that the photo-generated excitons can be dissociated into free charge carriers at the P3HT:PTB7-Th interface and reinforce the charge transfer between P3HT and PTB7-Th. In P3HT:PCBM binary organic solar cell, the photo-generated excitons only can be directly dissociated into free charge carriers at the P3HT:PCBM interface and then transported to the respective electrodes, while incorporating PTB7-Th, the interaction between P3HT and PTB7-Th also makes the photo-generated excitons dissociated at the interface of P3HT:PTB7-Th, and at the interface of PTB7-Th:PCBM. The increasing of excitons dissociated leads to a higher FF. The present study is the first report on utilizing PTB7-Th in P3HT:PCBM PSC.
Keywords: ternary polymer solar cells/
PTB7-Th/
exciton dissociation
