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

Abstract

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 is possible by using a ternary active layer consisting of either two donors (D) and one acceptor (A) or two acceptors and one donor having complementary absorption and appropriate frontier energy levels for efficient exciton generation and their dissociation into free charge carriers and subsequent charge/energy transfer. Herein, a large bandgap guaiacol‐based small molecule (SMD) is used as 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 (VOC). OSCs based on the optimized ternary blend P:SMD:Y6 (0.8:0.2:1.2, w/w) after solvent vapor annealing attained a higher VOC of 0.85 V and low energy loss of 0.51 eV compared with the binary device P:Y6 (1:1.2, w/w) with VOC of 0.81 V and energy loss of 0.55 eV, delivering an overall PCE of 15.37%.

Branched Alkoxy Side Chain Enables High-Performance Non-Fullerene Acceptors with High Open-Circuit Voltage and Highly Ordered Molecular Packing

“…During the past several years, non-fullerene acceptors (NFAs) have received extensive research attention in the field of organic solar cells (OSCs) for their attractive features, including excellent optical absorption properties, readily tunable structures and energy levels, adjustable solubility, and good crystallinity. − The recent progress of OSCs in the power conversion efficiencies (PCEs) has been driven by the development of emerging NFA molecules, especially the state-of-the-art A-DA′D-A-type molecules (A stands for the acceptor unit and D stands for the donor unit). − For instance, Y6 was the first reported A-DA′D-A-type NFA, and since then, our research community has seen breakthroughs in the PCEs of Y6-family OSC devices. − Y6 exhibits many attractive features, including excellent absorption properties, high crystallinity, and low voltage loss in the corresponding OSC devices. − Due to these advantages of Y6, the majority of our research community has been devoted to optimizing the chemical structures and improving the performance of Y6-based OSCs. − These modifications of Y6 include the modification on their skeletons, end groups, side chains, and center cores, which all yielded excellent photovoltaic performance and interesting structural property comparisons. ,− …”

Ternary Polymer Solar Cells Enabled Using Two Donor Polymers with Broad Absorption and Cascade LUMO Levels

“…Under short-circuit conditions, the J ph a / J sat value of the optimized ternary PSCs reached 95.9%, which was higher than 95.1 and 95.5% for D18-Cl:N3-based binary PSCs and ternary PSCs, respectively, with a D18-Cl:PTB7-Th:N3 ratio of 0.75:0.25:1.3, indicating more sufficient exciton dissociation. Under maximal power output conditions, the J ph b / J sat of the optimized ternary PSCs reached 85.3%, which was much higher than 84.7 and 85.0% for D18-Cl:N3-based binary PSCs and ternary PSCs, respectively, with a D18-Cl:PTB7-Th:N3 ratio of 0.75:0.25:1.3, indicating more efficient charge collection. , …”

“…Under maximal power output conditions, the J ph b /J sat of the optimized ternary PSCs reached 85.3%, which was much higher than 84.7 and 85.0% for D18-Cl:N3-based binary PSCs and ternary PSCs, respectively, with a D18-Cl:PTB7-Th:N3 ratio of 0.75:0.25:1.3, indicating more efficient charge collection. 36,37 The space-charge limited current (SCLC) method was employed to calculate the electron mobility (μ e ) and hole mobility (μ h ) in SCLC devices (the SCLC configuration and calculation method are shown in the Supporting Information). The measured curve and calculated electron and hole mobility values are shown in Figure 4 (a and b, respectively) and Table 4, respectively.…”

Efficient and Stable Ternary Organic Solar Cells Using Liquid Crystal Small Molecules with Multiple Synergies

“…The significantly lower P diss and P coll of BTR-Cl:N3 is responsible for its low J SC , and the addition of BTR-Cl to D18-Cl:N3 further improves P diss and P coll , which resulted in enhanced J SC for the TOSC. 43,44 The space charge-limited current (SCLC) method is used to calculate the electron mobility (μ e ) and hole mobility (μ h ) in the devices to study the charge transport characteristics. 34,45 Detailed device structure in the Supporting Information, using the results obtained from the calculation of eq S2 summarizes the J 0.5 −V curves for pure electron and pure hole devices as shown in Figure S7.…”