CPOS Seminar: "On Optoelectronic Processes in Organic Solar Cells: From Opaque to Transparent"

Speaker: NORA SCHOPP, Graduate Student Researcher, Chemistry and Biochemistry Department, UCSB

Abstract: Organic (semi)transparent photovoltaics (ST-OPVs) promise integrated, sustainable, low-cost energy harvesting solutions. However, current efficiency limitations must be overcome to make STOPV a competitive technology. In this talk, I discuss the effect of the transparency on the photoelectronic processes in ST-OPVs. Our simulation-based approach allows us to systematically vary the extinction coefficient while keeping all other parameters constant. This way, we can gain insights that are not accessible experimentally, quantifying changes in the generation–recombination dynamics and the extraction efficiency that are causally linked to the increased transparency. Our simulationbased findings give experimentally relevant insights into the alteration of processes in ST-OPVs and yield practical advice for the future development of ST-OPVs.
I will show that reduced generation rates and altered generation rate profiles lead to a reduced Voc and an increased relative bulk trap-assisted recombination contribution, indicating that highpurity and morphologically optimized active layers with low trap density are required. Transparent devices are more sensitive to shunt-leakage, which reinforces the requirement of a high-quality active layer. Furthermore, the effect of surface recombination at the active layer interfaces becomes less pronounced for systems with higher AVT and limitations due to high series resistance decrease, suggesting that a broader range of materials and deposition techniques can be considered for transparent electrodes. Furthermore, I will discuss the reduction of the short-circuit current, and show that the extraction efficiency increases with the AVT, counteracting to a small extent the decreased charge carrier generation rates.