[22p-P07-1~25] 12.5 Organic solar cells

▲ [22p-P07-3] Photovoltaic Behavior of Centimeter-Long Lateral Organic Junctions

〇(M2)Jaseela Palasheriithikkal^1,2, Adrien Girault^1,3, Mitsuru Kikuchi¹, Yusuke Yabara¹, Seiichiro Izawa^1,2, Masahiro Hiramoto^1,2 (1.Institute for Molecular Science, 2.The graduate university for advanced studies, SOKENDAI, 3.Chimie ParisTech Ecole nationale superieure de chimie de Paris)

Keywords:organic solar cells, long length carrier transport, mobility

Recently, we reported a lateral alternating multilayered junction using a high mobility organic semiconductor¹⁾. In this study, we fabricated lateral junction cells having distance reaching cm order (Fig. 1). A donor [C8-BTBT (m_h = 43 cm²V^-1s^-1)] – acceptor [PTCDI-C8 (m_e = 1.7 cm²V^-1s^-1)] combination was used. Buffer layers of BCP and MoO₃ were used for the selective carrier collection of electrons and holes, respectively (Fig. 1). Surprisingly, even lateral cells with L=1.8 cm showed clear photovoltaic behavior (Fig. 2, red curve). Fig. 3 shows the L dependence of observed J_sc (red curve) and calculated J_sc (blue curve) obtained from diffusion lengths of electrons (4.7 mm) and holes (5.5 mm), which are dominated by traps. These diffusion lengths were obtained by the experiments using the moving photomask covering the irradiated surface from respective electrodes. Thus, considerable decrease in photocurrent is attributed to the trap-assisted recombination indicated by the blue curve. A further difference between the observed and calculated curves is due to bimolecular recombination and its effect is small. Thus, we concluded that trap-assisted recombination can be the main reason for photocurrent loss of the long lateral cells. Hence, identifying and removing the defects acting as traps can be done to improve cell performance.
M. Kikuchi, et al, ACS Appl. Energy Mater., 2, 2087-2093 (2019).