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

Abstract

Stable and robust open-circuit voltage (V_OC) is essential to achieve a long lifetime for polymer solar cells (PSCs). Here, we investigate the V_OC burn-in loss mechanism on the basis of the analysis of electroluminescence quantum efficiency (EQE_EL) 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 V_OC burn-in loss. Moreover, varying the ETL significantly affected the degree of V_OC burn-in loss, although relative contribution of these two factors remained constant. To accurately extract charge recombination-induced V_OC loss, we applied a novel yet effective method that relates the EQE_EL of PSCs to charge recombination-induced V_OC loss. Additional analyses, including those focused on light intensity (P_light)-dependent V_OC and density of states, will provide an inclusive perspective on the degradation mechanism of V_OC and development of stable PSCs.