Incorporation of a Guaiacol-Based Small Molecule Guest Donor Enables Efficient Nonfullerene Acceptor-Based Ternary Organic Solar Cells

摘要

To improve the power conversion efficiency (PCE) of the organic solar cells(OSCs), it is necessary to widen the absorption profile of the active layer. It ispossible by using a ternary active layer consisting of either two donors (D) andone acceptor (A) or two acceptors and one donor having complementaryabsorption and appropriate frontier energy levels for efficient exciton generationand their dissociation into free charge carriers and subsequent charge/energytransfer. Herein, a large bandgap guaiacol-based small molecule (SMD) is usedas guest donor in ternary OSCs to improve the PCE and suppress the energy loss.SMD exhibits a lager bandgap and deeper highest occupied molecular orbital(HOMO) energy level compared with conjugated polymer donor (P). Therefore,the HOMO energy level is effectively down-shifted when P is mixed with SMD,which is beneficial for attaining high open circuit voltage (V_(OC)). OSCs based onthe optimized ternary blend P:SMD:Y6 (0.8:0.2:1.2, w/w) after solvent vaporannealing attained a higher V_(OC) of 0.85 V and low energy loss of 0.51 eVcompared with the binary device P:Y6 (1:1.2, w/w) with V_(OC) of 0.81 V and energyloss of 0.55 eV, delivering an overall PCE of 15.37%.