Synthesis of planar fluorenimine derivative-based broad band-gap polymers for bulk heterojunction polymer solar cells

Abstract

Two fluorenimine-based broad band-gap polymers PNFDTBF and PNFDTTz were synthesized by Suzuki polycondensation, and their thermal, electrochemical, optical and photovoltaic properties were investigated in detail. Through the introduction of versatile C=N double bond in fluorenimine unit, it can make the architecture of polymers more planar and induce lower band gaps. The optical band gaps of PNFDTBF and PNFDTTz can reach 1.90 and 1.99 eV, respectively. The hole mobilities were 2.78  ×  10⁻⁵ and 3.84  ×  10⁻⁵ cm² v⁻¹ s⁻¹ for PNFDTBF and PNFDTTz, respectively. The photovoltaic characterization under the device architecture of ITO/PEDOT-PSS/active layer/PFN/Al showed that short circuit current densities (J_scs), fill factors (FFs), open circuit voltage (V_ocs) and power conversion efficiencies for PNFDTBF and PNFDTTz were 1.16 mA cm⁻², 32%, 0.70 V and 0.48% and 1.27 mA cm⁻², 33%, 0.60 V and 0.44%, respectively.

Keywords:

• Fluorene
• Fluorenimine
• Polymer
• Broad band gap
• Polymer solar cells

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [Grant No. 51273069]; Research Fund for the Doctoral Program of Higher Education of China [Grant No. 20130172110005]; Fundamental Research Funds for the Central Universities [Grant No. 2014ZB0017].