Analysis of Interfacial Layer-Induced Open-Circuit Voltage Burn-In Loss in Polymer Solar Cells on the Basis of Electroluminescence and Impedance Spectroscopy.

Stable and robust open-circuit voltage (VOC) is essential to achieve a long lifetime for polymer solar cells (PSCs). Here, we investigate the VOC burn-in loss mechanism on the basis of the analysis of electroluminescence quantum efficiency (EQEEL) and impedance measurements in amorphous PSCs, with an inverted structure having different electron transport layers (ETLs) of ZnO nanoparticles (NPs) and the sol-gel processed ZnO layer. We found that both charge recombination and energetic disorder account for a substantial proportion of the VOC burn-in loss. Moreover, varying the ETL significantly affected the degree of VOC burn-in loss, although relative contribution of these two factors remained constant. To accurately extract charge recombination-induced VOC loss, we applied a novel yet effective method that relates the EQEEL of PSCs to charge recombination-induced VOC loss. Additional analyses, including those focused on light intensity (Plight)-dependent VOC and density of states, will provide an inclusive perspective on the degradation mechanism of VOC and development of stable PSCs.