Design and production of semi-transparent organic solar cells including photonic crystal

In this thesis, organic semiconductor-based bulk-heterojunction (BHJ) inverted organic solar cells (IOSC) with opaque and semi-transparent (ST) optical characteristics have been investigated. The active site of IOSCs is composed of a mixture of organic semiconductors poly (3-hexylthiophene-2, 5-diyl) (P3HT) as the donor and poly (6, 6-phenyl C61-butyric acid methyl ester) (PCBM) as the acceptor, the electron transport layer (ETL) and hole transporting layer (HTL) are composed of transition metal-oxide (TMO) material systems. The production and characterization of OSC structures, which are theoretically designed, examined and optimal values are determined, were carried out in Gazi University Photonics Application and Research Center. Within the scope of the thesis, the examination of OSCs can be considered methodologically in three parts. First, the IOSC structure that gives the best cell performance has been determined by using different HTL materials. Power conversion efficiency (PCE) values are taken as a reference in determining the IOSC with the best cell performance. Then, the high-performance opaque-IOSC structure with the appropriate HTL material is transformed into an ST-OSC structure with a dielectric/metal/dielectric (DMD) based transparent top contact. Optimal structural parameters with high average apparent transmittance (AVT) of the ST-OSC structure, which is designed considering AVT have been obtained. Finally, with the integration of one-dimensional (1D) photonic crystals (PC) into ST-OSCs, the color coordinates of the structures have been shifted towards the Planckian locus. In P3HT:PCBM based IOSCs, ZnO is used as ETL and MoO3, V2O5 and WO3 TMO material systems are used as HTL.mThe effects of each HTL layer on the optical, structural, and electrical properties of the IOSC were investigated by using transmittance, atomic force microscope (AFM), and current-voltage measurements, respectively. The HTL material that gives the best cell performance has been determined as MoO3, and the fill factor (FF) of the structure is 51.17% and the PCE value is 2.1%. The opaque top contact of the opaque-IOSC structure has been modified with the MoO3/Ag/ MoO3 DMD transparent top electrode for which the appropriate design parameters have been determined and ST-OSC structures have been designed. Theoretical absorption, transmittance and reflection characteristics of DMD and ST-OSC structures have been calculated using the transfer matrix method (TMM). By changing the MoO3/Ag/ MoO3 layer thicknesses in the designs, the optimal structure parameters with the highest AVT value were determined and the ST-OSC structure was produced at these values. Theoretically 38.52% and experimentally 37.42% AVT values have been obtained. The modification of the color coordinates of the ST-OSC structure with a high AVT value (MgF2/MoO3)N has been carried out with the integration of the 1D-PC system. It was determined that the color coordinates of ST-OSC shifted to the Planckian locus and D65 color coordinates by using (MgF2/MoO3)N 1D-PC designed with N=4 period and 700 nm Bragg wavelength (λ_B). For this structure, x ve y are determined as 0.3248 and 0.3733, respectively, and the AVT value is calculated as 18.63%. In ST-OSC designs containing 1D-PC, it has been determined that the Δ_(u,v)<0.0054 requirement for CCT determination is valid only for λ_B=725 nm at N=4 and 8 periods. At λ_B=725 nm, Δ_(u,v) values for N=4 and 8 periods are 0.0031 and 0.0039, respectively, and CCT values are 3483 K and 3161 K, respectively. It has also been observed that the CRI values of ST-OSCs are significantly reduced with the integration of 1D-PC. It has been determined that the cell performance of ST-OSC is positively affected by the (MgF2/MoO3)N PC system. It was observed that J_sc in ST-OSC containing 1D-PC was higher than that of ST and less than that of opaque one. The FF value of the ST-OSC structure with a photonic band gap (PBG) in N=4 periods at λ_B 700 nm is 53.61% and PCE value is 1.90%. Finally, as a result of detailed calculations and examinations on the OSCs produced at optimal values, it has been determined that the optical properties of the structure can be modified and the color coordinates can be shifted to the Planckian locus, as well as the cell output parameters can be improved with an ST-OSC design including 1D-PC.