High-performance ternary blend polymer solar cells involving both energy transfer and hole relay processes.

Luyao Lu,Luping Yu,Wei Chen,Tao Xu

doi:10.1038/ncomms8327

Abstract

The integration of multiple materials with complementary absorptions into a single junction device is regarded as an efficient way to enhance the power conversion efficiency (PCE) of organic solar cells (OSCs). However, because of increased complexity with one more component, only limited high-performance ternary systems have been demonstrated previously. Here we report an efficient ternary blend OSC with a PCE of 9.2%. We show that the third component can reduce surface trap densities in the ternary blend. Detailed studies unravel that the improved performance results from synergistic effects of enlarged open circuit voltage, suppressed trap-assisted recombination, enhanced light absorption, increased hole extraction, efficient energy transfer and better morphology. The working mechanism and high device performance demonstrate new insights and design guidelines for high-performance ternary blend solar cells and suggest that ternary structure is a promising platform to boost the efficiency of OSCs.

Highlights

The integration of multiple materials with complementary absorptions into a single junction device is regarded as an efficient way to enhance the power conversion efficiency (PCE) of organic solar cells (OSCs)
A highly efficient ternary structure polymer solar cells (PSCs) is developed by adding PID2 as the additional donor polymer into the PTB7-Th:phenyl C71 butyric acid methyl ester (PC71BM) binary device
A PCE of 9.20% was achieved with 20% of PID2 incorporation, which is the highest PCE reported for ternary PSCs

Summary

Introduction

The integration of multiple materials with complementary absorptions into a single junction device is regarded as an efficient way to enhance the power conversion efficiency (PCE) of organic solar cells (OSCs). Detailed studies unravel that the improved performance results from synergistic effects of enlarged open circuit voltage, suppressed trap-assisted recombination, enhanced light absorption, increased hole extraction, efficient energy transfer and better morphology. In addition to a complementary absorption with the primary donor material in the solar spectrum and cascade energy levels between highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the dominating donor polymer and fullerene acceptor to facilitate charge transport[17,26], our recent results revealed that the ternary blend exhibits improved nanomorphology over the binary device by carefully selecting the third component used. The results indicate that the mechanism of the enhancement is completely different from our recent work based on donor polymer PTB7 (ref. 27)

Methods

Results

Conclusion