Tandem polymer solar cells: simulation and optimization through a multiscale scheme.

Fanan Wei,Fei Lan,Ligang Yao,Guangyong Li,Lianqing Liu

doi:10.3762/bjnano.8.13

Abstract

In this paper, polymer solar cells with a tandem structure were investigated and optimized using a multiscale simulation scheme. In the proposed multiscale simulation, multiple aspects – optical calculation, mesoscale simulation, device scale simulation and optimal power conversion efficiency searching modules – were studied together to give an optimal result. Through the simulation work, dependencies of device performance on the tandem structures were clarified by tuning the thickness, donor/acceptor weight ratio as well as the donor–acceptor distribution in both active layers of the two sub-cells. Finally, employing searching algorithms, we optimized the power conversion efficiency of the tandem polymer solar cells and located the optimal device structure parameters. With the proposed multiscale simulation strategy, poly(3-hexylthiophene)/phenyl-C61-butyric acid methyl ester and (poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b]dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)])/phenyl-C61-butyric acid methyl ester based tandem solar cells were simulated and optimized as an example. Two configurations with different sub-cell sequences in the tandem photovoltaic device were tested and compared. The comparison of the simulation results between the two configurations demonstrated that the balance between the two sub-cells is of critical importance for tandem organic photovoltaics to achieve high performance. Consistency between the optimization results and the reported experimental results proved the effectiveness of the proposed simulation scheme.

Highlights

Polymer solar cells, known as organic solar cells, have been attracting a wealth of attention due to their great potential as an alternative to the presently extensively used inorganic solar cells
We found that most of the simulation work was focused on tuning the thickness of active layers [20], while efforts were rarely devoted to the optimization of the internal material distribution and D/A weight ratio in the active layers of tandem organic solar cells
From the optical calculation module, the photon absorption efficiency (Figure 3c,d) of the two active layers were computed under varied thickness values for the two layers

Summary

Introduction

Known as organic solar cells, have been attracting a wealth of attention due to their great potential as an alternative to the presently extensively used inorganic solar cells. Considering the strong optical and electrical coupling between the two sub-cells in tandem photovoltaics, to optimize device performance, it is essential to tune the thickness of both active layers. We found that most of the simulation work was focused on tuning the thickness of active layers [20], while efforts were rarely devoted to the optimization of the internal material distribution and D/A weight ratio in the active layers of tandem organic solar cells.

Results

Conclusion