Glucose and Its Derivatives as Interfacial Materials for Inverted Organic Solar Cells

Glucose, a widely distributed biomaterial in nature, is presented as a new cathode interfacial material for highly efficient inverted organic solar cells. The interactions between glucose and the indium tin oxide (ITO) substrate as well as the formation mechanisms of the glucose interlayer were investigated by molecular dynamics simulation and relevant experimental tests. The results revealed that the In-OH coordination between the oxygen atom of glucose and the indium of ITO is the key factor for the formation of interfacial dipoles, thereby reducing the work function of the ITO cathode for efficient charge transfer. With PM6:Y6 as the active layer, the power conversion efficiency (PCE) of the organic solar cells was significantly increased from 1.99 to 15.42% after ITO was modified by a glucose interlayer through the traditional spin-coating method. More importantly, glucose can be adsorbed on the ITO surface by a simple immersion process, and the devices based on the modified ITO by immersed glucose achieved a PCE of 14.48%, which is comparable to that of the traditional spin-coating method. Furthermore, we found that the OSCs with the ITO cathodes modified with glucose derivatives including sorbitol and sodium gluconate by different preparation methods also exhibited high performance. The overall performance of the devices with ITO modified by a simple and low-cost immersion method can be maintained at more than 93% of that prepared with the traditional spin-coating method. The results demonstrated that low-price glucose and its derivatives are good candidates as ITO interlayer materials for OSCs, and the effectiveness of the immersion process paves a way for simplifying the manufacture of low-cost and large-area organic solar cells.