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.