Enhancing Efficiency of Organic Bulkheterojunction Solar Cells by Using 1,8-Diiodooctane as Processing Additive
Organic solar cells (OSCs) are attractive as an al- ternative to inorganic devices for their easy fabrication and solution-processability. A major and unsolved problem with bulk heterojunction devices remains the optimization of the network morphology. Here, we discuss the influence of the 1,8-diiodooctane (DIO) solvent additive on the efficiency of OSCs and show that by selectively controlling the crystallization of the organic ma- terial, the power conversion efficiency (PCE) can be increased by about 30%. For P3HT:PCBM-based devices, the power con- version efficiency (PCE) was increased from 3.7% to 4.9% for PCPDTBT:P3HT:PCBM-based devices from 3.2% to 4.1%. This improvement is due to the higher I/subSCsub/ , which is in agreement with the higher external quantum efficiency (EQE) observed on the de- vices fabricated with DIO. We correlate this to an increase of the surface roughness observed with atomic force microscopy (AFM) analysis. We demonstrate that the effect of the DIO additive is equivalent to a high-temperature thermal annealing.
Francesco Arca (@Francesco)
Published in
OrganicElectronics
· 10 Jun 2018
I. INTRODUCTION OVER the past few years, interest in cheap photovoltaic solutions has increased because of growing demand for renewable energy sources. Polymer-based organic solar cells (OSCs) offer a cost-effective option for solar energy conver- sion and are attractive as a solution-processable alternative to classical inorganic photovoltaic solutions. The most commonly used materials for polymeric solar cell fabrication are Poly(3-hexylthiophen-2,5-diyl) (P3HT) as electron donor and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as electron acceptor [1]. Recent reports have shown that this material combination can reach power conve...