Development of high optical performance polymer-based solar cell structures

In this thesis, it is aimed to design and fabricate PTB7-based organic solar cells with high optical performance and to investigate their optical and photovoltaic properties. In the scope of the thesis study, optical properties such as average visible transmittance (AVT), color rendering index (CRI), correlated color temperature (CCT) and color perception were examined over 10,000 theoretically calculated cell designs to determine the optimal semi-transparent organic solar cells with MoO3/Ag/WO3 asymmetric DMD integrated active region PTB7:PC71BM blend with different advantages. This optimization was carried out by performing Transfer Matrix Method (TMM) calculations. As a result of the calculations performed within the scope of the thesis, the structure with maximum AVT (AVTmax) and the structure with maximum CRIext ((CRIext)max), where optical properties become prominent in line with the set targets, and the structure with the most extreme color (Extreme Color) that can be achieved without integrating a new photonic-based system into the structure have been produced. In addition, two different color regions selected as a result of the TMM calculations for integrating 1D-PC into the structure with the highest AVT to reach the colored solar cell were fabricated. Furthermore, the bifaciality properties of the fabricated structures were examined in line with a different target. While the theoretically calculated AVT value for the AVTmax is 48.75%, the experimental AVT value for the fabricated one was found to be 47.14%. For the (CRIext)max, CRIext was theoretically 99 and experimentally 97. The theoretical and experimental AVT values for (CRIext)max were found to be 22.29% and 23.82%, respectively, while PCE was 6.21%. In this thesis, using the CIE x, y coordinates determined by TMM calculations, an "Extreme Color" structure that can change the color to the extreme point above the 25% AVT limit was determined. The experimental AVT value of the structure, which has a theoretical AVT value of 25.15%, has an experimental AVT value of 26.34% and a PCE value of 5.81%. With the calculations in the scope of light management engineering, 1D-PC was integrated on the structure and structures with an AVT value above 25% and can be used with different color properties in window applications were designed. As a result of the calculations made using TMM, two extreme color regions were determined. In order to achieve the yellow color target, a 5-period structure of the (MgF2/WO3)N 1D-PC system with λ_B at 425 nm was selected. For the blue color, which can be reached as another endpoint, a 3-period structure of the (MgF2/WO3)N 1D-PC system with λ_B at 650 nm was selected. The solar cells designed as semi-transparent have the potential to be used as bifacial, so the bifacial properties of the structures produced in this thesis were examined. As a consequence of the investigation, the bifaciality parameter for the AVTmax structure was found to be 0.94, while it was determined as 0.25 and 0.34 for the (CRIext)max and "Extreme Color" structures, respectively. The bifaciality parameter obtained for the AVTmax is essential in terms of showing the bifaciality potential of such a structure. As a result of the thesis study, with detailed calculations based on light management engineering, cell structures exhibiting the targeted high optical performance were designed and fabricated, and the targeted increases in photovoltaic performance were achieved.