protocols that tailor the absorption spectrum of the active material. [1][2][3][4][5][6] While such efforts have resulted in a library of active materials, they have also presented challenges for commercial viability due to the different processes and costs associated with employing distinct active materials to display different colors. Their use has also resulted in varied performances among devices of different colors, adding to the difficulty for practical implementation. Furthermore, challenges in organic synthesis have limited the achievable types of color and their spectral purity. In this work, we introduce a strategy that enables a single active material that absorbs uniformly across the visible range to display different colors with high spectral purity and consistent device performances through the implementation of a color filtering (CF) electrode. The electrode consists of a Ag-TiO x -Ag Fabry-Perot (FP) resonant cavity, where the thickness of the TiO x layer determines the spectral position of the transmission peak and the inner Ag layer functions as an electrical contact. The electrode also functions as a mirror for all wavelengths of light except that within the resonant band (i.e., the spectral transparency window) of the CF. Therefore, light that has not been selectively transmitted may reflect back into the active material, contributing to additional charge generation. This implies that the short-circuit current density, which is largely a function of the optical absorption, must be higher for a CF-integrated OPV compared to a transparent OPV, under the condition that the two devices show similar peak transmission efficiencies.The use of photonic structures as optical filters in OPVs or inorganic solar cells has been previously reported in the form of distributed Bragg reflectors, [7][8][9] photonic arrays, [10][11][12] and plasmonic resonators. [13][14][15] While such filters enable various colors to be transmitted or reflected through tuning of the characteristic dimension of the filter components, in many cases they suffer from increased fabrication costs and duration because of the structural complexity. Moreover, photonic structures employing low-loss dielectrics exhibit poor electrical conductivity, precluding their use as an electrode. Finally, the structural anisotropy intrinsic to 1D or 3D photonic structures can result in asymmetric responses for light incident from above and below the device. Such behavior can complicate design schemes for creating bidirectional colored windows.Colorful, semitransparent organic photovoltaic cells (OPVs) are increasing in demand due to their applicability in aesthetically fashioned powergenerating windows. The traditional method of generating different colors in OPVs has been through employing different active materials exhibiting distinct absorption spectra. This can complicate fabrication processes for production and cause deviations in device performance among differently colored OPVs. Herein, semitransparent and colorful OPVs with a single broadban...

Semitransparent colorful organic solar cells (OSC) provide exciting opportunities for harnessing sunlight as colored windows. Previously, color filter (CF) electrodes on (OSC) were demonstrated via vacuum-deposition techniques, resulting in deposition-induced damage. Thus, we present CF integrated organic photovoltaics (CF-OPVs) using solution-processed TiO2–AcAc as the dielectric component. The noninvasive processing substantially expands the range of usable active materials, allowing the device to display pure and vibrant colors that are independent of the inherent color of the active material and show superior optical and photovoltaic characteristics. These results provide practical pathways to realizing colored semitransparent solar cells.

Abstract:A morphologically-stable polymer/fullerene heterojunction has been prepared by minimizing the intermixing between polymer and fullerene via sequential deposition (SqD) of a polymer and a fullerene solution. A low crystalline conjugated polymer of PCPDTBT (poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b ]dithiophene)-alt-4,7(2,1,3-benzothiadiazole)]) has been utilized for the polymer layer and PC 71 BM (phenyl-C 71 -butyric-acid-methyl ester) for the fullerene layer, respectively. Firstly, a nanostructured PCPDTBT bottom layer was developed by utilizing various additives to increase the surface area of the polymer film. The PC 71 BM solution was prepared by dissolving it in the 1,2-dichloroethane (DCE), exhibiting a lower vapor pressure and slower diffusion into the polymer layer. The deposition of the PC 71 BM solution on the nanostructured PCPDTBT layer forms an inter-digitated bulk heterojunction (ID-BHJ) with minimized intermixing. The organic photovoltaic (OPV) device utilizing the ID-BHJ photoactive layer exhibits a highly reproducible solar cell performance. In spite of restricted intermixing between the PC 71 BM and the PCPDTBT, the efficiency of ID-BHJ OPVs (3.36%) is comparable to that of OPVs (3.87%) prepared by the conventional method (deposition of a blended solution of polymer:fullerene). The thermal stability of the ID-BHJ is superior to the bulk heterojunction (BHJ) prepared by the conventional method. The ID-BHJ OPV maintains 70% of its initial efficiency after thermal stress application for twelve days at 80 • C, whereas the conventional BHJ OPV maintains only 40% of its initial efficiency.

Colorful indoor organic photovoltaics (OPVs) have attracted considerable attention in recent years for their autonomous function in internet-of-things (IoT) devices. In this study, a solutionprocessed TiO 2 layer in a metal-oxide-metal (MOM) color filter electrode is used for light energy recycling in P3HT:ICBA-based indoor OPVs. The MOM electrode allows for tuning of the optical cavity mode to maximize photocurrent production by modulating the thickness of the TiO 2 layer in the sandwich structure. This approach preserves the OPVs' optoelectronic properties without damaging the photoactive layer and enables them to display a suitable range of vivid colors. The optimized MOM-OPVs demonstrated an excellent power conversion efficiency (PCE) of 8.8%±0.2%, which is approximately 20% higher than that of reference opaque OPVs under 1000 lx light emitting diode illumination. This can be attributed to the high photocurrent density due to the nonresonant light reflected from metals into the photoactive layer. Additionally, the proposed MOM-OPVs exhibited high external quantum efficiency and large parasitic shunt resistances, leading to improved fill factor and PCE values. Thus, the study's MOM electrode provides excellent feasibility for realizing colorful and efficient indoor OPVs for IoT applications.

Low dark current (off-current) and high photo current are both essential for a solution processed organic photodetector (OPD) to achieve high photo-responsivity. Currently, most OPDs utilize a bulk heterojunction (BHJ) photo-active layer that is prepared by the one-step deposition of a polymer:fullerene blend solution. However, the BHJ structure is the main cause of the high dark current in solution processed OPDs. It is revealed that the detectivity and spectral responsivity of the OPD can be improved by utilizing a photo-active layer consisting of an interdiffused polymer/fullerene bilayer (ID-BL). This ID-BL is prepared by the sequential solution deposition (SqD) of poly(3-hexylthiophene) (P3HT) and [6,6] phenyl C61 butyric acid methyl ester (PCBM) solutions. The ID-BL OPD is found to prevent undesirable electron injection from the hole-collecting electrode to the ID-BL photo-active layer resulting in a reduced dark current in the ID-BL OPD. Based on dark current and external quantum efficiency (EQE) analysis, the detectivity of the ID-BL OPD is determined to be 7.60 × 10(11) Jones at 620 nm. This value is 3.4 times higher than that of BHJ OPDs. Furthermore, compared to BHJ OPDs, the ID-BL OPD exhibited a more consistent spectral response in the range of 400 - 660 nm.