Suhee Ro1 Shinyoung Choi1 Boseul Choi1 Yukyung Shin1 BongSoo Kim1

1, Ewha Womans University, Seoul, , Korea (the Republic of)

We report the synthesis of a narrow-band-gap, anionic conjugated polyelectrolyte, PCPDT-FBT-SO3K and PCPDT-F2BT-SO3K for applying to the hole-transporting layer (HTL). Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been extensively used as HTL in bulk heterojunction (BHJ) solar cells. However, its anisotropic electrical conduction and intrinsic acidic nature limit the device performance and stability. To overcome these drawbacks of PEDOT:PSS, PCPDT-BT-SO3K was synthesized which has properties of homogeneous electrical conduction, neutral PH. Though PCPDT-BT-SO3K enhanced power conversion efficiency (PCE), organic photovoltaic device using PCPDT-BT-SO3K displayed reduced an open-circuit voltage (Voc) compared with device using PEDOT:PSS as HTL. By contrast, newly synthesized PCPDT-FBT-SO3K and PCPDT-F2BT-SO3K polymers increasing work function of ITO substrates exhibited higher PCEs with higher Voc than PCPDT-BT-SO3K polymer. Overall, this work demonstrate the chemical tuning of conjugated polyelectrolytes can improve the photovoltaic performance of organic solar cells.