Abstract
In recent years, ternary organic photovoltaic cells (OPVs) have been dedicated to improving power conversion efficiency (PCE) by broadening optical absorption spectra. Ternary OPVs with different poly[thieno[3,2-b]thiophene-2,5-diyl-alt-4,9-bis(4-(2-decyltetradecyl)thien-2-yl)naphtho[1,2-c:5,6-c’]bis[1,2,5]thiadiazole-5,5′-diyl] (PTT-DTNT-DT) doping concentrations were designed and the effect of PTT-DTNT-DT as a complementary electron donor on the performance of OPVs was investigated. The optimized PCE of OPVs was increased from 3.42% to 4.66% by doping 20 wt % PTT-DTNT-DT. The remarkable improvement in the performance of the ternary device is mainly attributed to the sharp increase in the short-circuit current density and fill-factor. The major reasons have been systematically studied from atomic force microscopy, electrochemical impedance spectroscopy, surface energy, space charge limited current and photocurrent behavior. It has been found that the separation of excitons and the transportation of charge are enhanced while light absorption is increased, and the charge recombination also decreases due to the optimization of the cascade energy level and the morphology of the ternary active layer. The results show that it is feasible to improve the performance of ternary OPVs by their complementary absorption.
Highlights
Bulk heterojunction (BHJ) organic photovoltaic cells (OPVs) have been widely developed for their advantages of low cost, low environmental pollution, simple process and large area preparation [1,2,3].Many strategies have been devised to elevate OPVs performance; for example, designing new device structures [4], designing and synthesizing high-performance materials [5,6], using effective interlayers [7], and optimizing device morphology [8,9]
It has been found that the separation of excitons and the transportation of charge are enhanced while light absorption is increased, and the charge recombination decreases due to the optimization of the cascade energy level and the morphology of the ternary active layer
The results show that it is feasible to improve the performance of ternary OPVs by their complementary absorption
Summary
Bulk heterojunction (BHJ) organic photovoltaic cells (OPVs) have been widely developed for their advantages of low cost, low environmental pollution, simple process and large area preparation [1,2,3].Many strategies have been devised to elevate OPVs performance; for example, designing new device structures [4], designing and synthesizing high-performance materials [5,6], using effective interlayers [7], and optimizing device morphology [8,9]. The power conversion efficiency (PCE) has been greatly improved in the recent decade, it is still restricted by a few factors, such as insufficient optical absorption and low carrier mobility [10,11]. Ternary strategy has emerged as an effective technique to improve photon capture and charge carrier mobility, and maintain a simple manufacturing process for single-layer active devices, rather than more complex tandem cells [12]. For ternary blend OPVs with “two donors/one acceptor”, the third component should be a material whose absorption spectral is complementary with that of the host system; this was helpful to improve the photonic capture performance of active layers with different bandgap materials [13,14,15,16,17,18,19,20,21,22].
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