Performance of Flexible MAPbI₃ Solar Cells Made on Different Transparent Conducting Electrodes with Different Hole Transport Layers

Perovskite solar cells (PSCs) have gained interest as a viable technology in recent years because of their low fabrication cost, solution processability, and high-power conversion efficiency. Commercializing perovskite solar cells requires high-throughput and low-cost manufacturing, e.g., solution-based roll-to-roll (R2R) process for making flexible PSCs. Transparent conducting electrodes (TCEs) are critical for flexible PSCs to achieve high efficiency. In our laboratory, flexible hybrid TCEs are made on polyethylene terephthalate (PET) with R2R flexographically printed Ag metal lines by blade coating silver nanowires (AgNWs) and planarized with indium zinc oxide (IZO) on top, and then the entire stack is photonic cured. With this process, we achieve TCEs with transmittance averaged between 400 and 700 nm wavelengths (T_avg ) = 81 ± 0.4 %, sheet resistance (R_sh ) = 11 ± 0.5 Ω/sq, and root-mean-square surface roughness (σ_rms) = 4.3 ± 0.4 nm. Flexible PSCs were fabricated on the hybrid TCEs and compared to devices made on commercially available PET/TCEs. We also investigated the J-V characteristics of these flexible PSCs using different hole transport layer materials. TCEs with comparable electrical, optical, and morphological properties displayed varied J-V performance with different hole transport layers. These results are surprising because, normally, other than transmittance and sheet resistance, TCEs are not considered to have a great effect on solar cell performance. We perform additional studies to probe the factors that influence the J-V characteristics of these flexible PSCs, such as contact resistance losses and interfacial properties between the TCE and the charge transport layers. The size of devices is also varied to study upscaling behavior. We aim to understand the charge extraction and recombination process and gain insights into the underlying mechanism affecting the performance and efficiency of flexible PSCs.<br/><br/>This work is supported by DOE SETO DE-EE0009518.