ITO‐free organic solar cells are fabricated on glass and on flexible substrates. The efficiencies of these cells on glass and plastic substrates (3.27% and 2.8%, respectively) were comparable to those of ITO‐based devices (3.66% and 2.9%, respectively). Furthermore, in the flexibility test the ITO‐free cells on flexible substrates manifested superior mechanical robustness compared with ITO‐based cells.

To enhance solar harvesting in organic solar cells, uniform-sized metal nanoparticles of ∼13 nm were incorporated to the device via pulse-current electrodeposition, which is a kind of simple and quick solution process that can control the density and size of metal nanoparticles. By incorporating plasmonic Ag nanoparticles on surface modified transparent electrodes, overall power conversion efficiency was increased from 3.05% to 3.69%, mainly resulting from the improved photocurrent density as a result of enhanced absorption of the photoactive conjugate polymer due to the high electromagnetic field strength in the vicinity of the excited surface plasmons.

Changes in the nanoscale morphologies of the blend films of poly (3‐hexylthiophene) (P3HT) and [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM), for high‐performance bulk‐heterojunction (BHJ) solar cells, are compared and investigated for two annealing treatments with different morphology evolution time scales, having special consideration for the diffusion and aggregation of PCBM molecules. An annealing condition with relatively fast diffusion and aggregation of the PCBM molecules during P3HT crystallization results in poor BHJ morphology because of prevention of the formation of the more elongated P3HT crystals. However, an annealing condition, accelerating PCBM diffusion after the formation of a well‐ordered morphology, results in a relatively stable morphology with less destruction of crystalline P3HT. Based on these results, an effective strategy for determining an optimized annealing treatment is suggested that considers the effect of relative kinetics on the crystallization of the components for a blend film with a new BHJ materials pair, upon which BHJ solar cells are based.

Polymer‐based photovoltaic cells, with periodic sub‐micrometer structures as an efficient light‐trapping scheme, are investigated to improve the performance of organic solar cells based on poly(3‐hexylthiophene) and 1‐(3‐methoxycarbonyl)propyl‐1‐phenyl‐(6,6)C61. A soft lithographic approach that uses photoresponsive azo polymer films as masters and poly(dimethylsiloxane) as stamps is used to form surface relief gratings (SRGs) on the active layers. The effect of periodic gratings on solar cell performance is precisely investigated according to various grating conditions such as period, depth, and dimension. The solar cells with 1D and 2D SRGs present improved incident‐photon‐to‐current conversion efficiencies and an overall increase in power conversion efficiencies, primarily resulting from the enhancement of short‐circuit current density, indicating that periodic structures induce further photon absorption in the active film.

The preparation of a reduced graphene oxide (pr‐Go) is with a novel p‐TosNHNH2 reductant is demonstrated for use as an efficient anode interfacial layer for high‐performance and highstability organic solar cells (OSCs). The efficiency of the cells with pr‐GO is highly comparable to those of the PEDOT:PSSbased devices. Furthermore, the pr‐GO based OSCs show a much longer cell life time in air stability tests in comparison with PEDOT:PSS‐based cells.