Ternary Organic Solar Cells with Minimum Voltage Losses

5 years ago

Ternary Organic Solar Cells with Minimum Voltage Losses

Olle Inganäs, Xiaofeng Xu, Xiangyi Meng, Chuanfei Wang, Mats Fahlman, Jonas Bergqvist, Arkady Yartsev, Xianjie Liu, Zewdneh Genene, Wei Ma, Wei Zhang, Ergang Wang

A new strategy for designing ternary solar cells is reported in this paper. A low-bandgap polymer named PTB7-Th and a high-bandgap polymer named PBDTTS-FTAZ sharing the same bulk ionization potential and interface positive integer charge transfer energy while featuring complementary absorption spectra are selected. They are used to fabricate efficient ternary solar cells, where the hole can be transported freely between the two donor polymers and collected by the electrode as in one broadband low bandgap polymer. Furthermore, the fullerene acceptor is chosen so that the energy of the positive integer charge transfer state of the two donor polymers is equal to the energy of negative integer charge transfer state of the fullerene, enabling enhanced dissociation of all polymer donor and fullerene acceptor excitons and suppressed bimolecular and trap assistant recombination. The two donor polymers feature good miscibility and energy transfer from high-bandgap polymer of PBDTTS-FTAZ to low-bandgap polymer of PTB7-Th, which contribute to enhanced performance of the ternary solar cell. Ternary solar cells with minimum voltage losses around 0.25 eV are designed by combining two donor polymers with same bulk and interface energy which make the hole transportation like in one donor polymer. The voltage losses were minimized due to EICT+ ≈ EICT−, where the trade-off between enhancing of charge generation and charge recombination by ICT states arrives at sweet spot.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/aenm.201700390