[23p-B103-1~13] 12.5 Organic solar cells

▼ [23p-B103-6] Unravelling complex performance-limiting factors of brominated ITIC-derivatives:PM6 organic solar cells by using time-resolved measurements

〇(D)Shaoxian Li¹, Ryosuke Nishikubo¹, Tatsuho Wada², Tomokazu Umeyama², Hiroshi Imahori³, Akinori Saeki¹ (1.Osaka Univ., 2.Hyogo Univ., 3.Kyoto Univ.)

Keywords:organic solar cell, charge transport dynamics, power conversion efficiency

The power conversion efficiency (PCE) of non-fullerene acceptor (NFA) organic solar cells (OSCs) has exceeded 19%, while the roles of many contributing factors are still vague. In this work, we measured the charge carrier dynamics in three end-group-brominated ITIC (β, γ, δ):PM6 OSCs using simultaneous time-of-flight (TOF) and time-resolved microwave conductivity (TRMC) and charge extraction by linearly increasing voltage (CELIV) techniques. The measured PCE was ITIC-γ:PM6 (9.3%)> ITIC-β:PM6 (8.5%)> ITIC:PM6 (7.5%)> ITIC-δ:PM6 (2.3%). TOF-TRMC and CELIV results revealed that ITIC-γ:PM6 has both low electron and hole mobilities, while its mobility relaxation was moderate among the OSCs. In contrast, ITIC-γ:PM6 showed the smallest bimolecular recombination coefficient. Further, we found the reduced domain size, shortened π-π stacking distance, red-shifted UV-vis absorption and enhanced charge separation efficiency seem to be more decisive for the higher PCE of ITIC-γ:PM6 than carrier mobility. Finally, regression coefficients of 13 parameters were calculated, rendering a clearer understanding of PCE determination in NFA OSCs.