Green fluorescence material TBRb enhancing the performance of ternary polymer solar cells via prolonged exciton lifetime and efficient energy transfer

Abstract

In this study, ternary polymer solar cells (PSCs) were prepared using a D18-Cl:N3 binary film as the host system and 2,8-di(t-butyl)-5,11-di[4-(t-butyl) phenyl]-6,12-diphenylnaphthacene (TBRb) as the third component material. The open-circuit voltage (V_OC) and fill factor (FF) exhibited minimal variation when added small amount of TBRb into D18-Cl:N3 binary film, indicating the formation of a compatible interface between D18-Cl:N3 and TBRb. The power conversion efficiency (PCE) of the optimized ternary PSC (D18-Cl:N3:TBRb ratio of 1:1.3:0.15) increased from 16.25% to 17.27%, and the short-circuit current density (J_SC) increased from 25.62 mA cm⁻² to 27.35 mA cm⁻² relative to that of the D18-Cl:N3 binary PSC. The observed increase in J_SC can be attributed to two factors: first, the energy transfer from TBRb to D18-Cl; second, the TBRb complements the light absorption of the D18-Cl:N3 binary film, particularly in the short-wavelength region. An excess of TBRb results in poor compatibility with D18Cl, which may result in a weakening of the acceptor–donor layer interpenetration. Thus, the excess TBRb disrupts the phase separation and surface morphology and subsequently reduces the exciton dissociation and charge transport and collection efficiencies. Consequently, high-TBRb ternary PSCs exhibited the lowest photovoltaic performance, accompanied by simultaneous reductions in the V_OC, J_SC and FF values. This study provides guidance for the selection of green fluorescent materials as the third component with appropriate compatibility with the binary host photoactive layer.