Optimization of interconnecting layers for double- and triple-junction polymer solar cells

In solution-processed tandem polymer solar cells, one of the most challenging parts is the optimization of interconnecting layers (ICLs) between subcells. In this study, ICLs were optimized for double- and triple-junction polymer solar cells. We investigated the robustness of PEDOT:PSS/AZO/PEIE ICL for tandem polymer solar cells. Solvent testing for ICL robustness showed a uniform coverage of the PEDOT:PSS layer when prepared without adding DMSO and IPA in PEDOT:PSS and with no use of additional filters. The performance of tandem polymer solar cells was investigated on different temperatures of interfacial layer. The PEDOT:PSS annealing temperature can be used from 120 °C to 130 °C, while aluminum-doped zinc oxide (AZO) temperature can be used from 120 °C to 150 °C. Lowering the annealing temperature in ICLs might help to fabricate triple-junction solar cells because they require more layers, and some low-bandgap polymers cannot sustain high temperature. However, reduction in annealing temperature in PEDOT:PSS, AZO, and PEIE led to lower FF and J_sc. A double-junction device V_oc of 1.05 V and a triple-junction V_oc of 1.4 V indicated that the ICLs worked effectively.