We developed a stable poly(3-hexylthiophene) (P3HT) nanowire (NW) dispersion solution and applied it to various organic solar cells (OSCs) effectively. In addition, we characterized the interfacial morphology of active layers (ALs) with P3HT NWs and found that they contribute significantly to light absorption. With the inclusion of P3HT NWs in ALs, OSCs based on P3HT donor and indene-C60 bisadduct (ICBA) acceptor showed power conversion efficiency (PCE) improvements for both bulk hetero junction (BHJ)- and bilayer (BL)-structure AL devices. The PCE increase was ~14% for both types of P3HT:ICBA OSCs. The variations in FF with respect to Voc and the equivalent-circuit parameters based on a non-ideal diode model have been discussed. We demonstrated a 47.1% efficiency improvement resulting from the combination of device-architecture modification and the inclusion of P3HT NWs in BHJ ALs. The modeling of ellipsometry spectra showed substantial changes in inhomogeneity and optical constants of the BHJ ALs with the inclusion of P3HT NWs. The operating characteristics of the nominal BL OSCs, the ALs of which consisted of sequentially cast bottom P3HT donor and top ICBA acceptor layers, resembled those of the OSCs with BHJ ALs. Optical analysis and device simulations showed that such resemblance could be attributed to the similarity in micromorphology of the ALs. Separate assessments of the exciton generation and the charge-carrier transport and/or extraction revealed that the contribution of P3HT NWs was more prominent in optical effects.
