Balancing Intermolecular Interactions between Acceptors and Donor/Acceptor for Efficient Organic Photovoltaics

Abstract

Promoted by uninterrupted materials and device innovation, organic solar cells have achieved impressive development. However, the complicated intermolecular interactions inside active layers are less understood. Herein, the intermolecular interactions are studied from the dual perspectives of acceptor/acceptor (A/A) and donor/acceptor (D/A), and how these interactions synergistically control the final efficiencies. Three small molecular acceptors (SMAs) are designed with different end-caps, which manipulate the crystallinity and electrostatic potential (ESP) distributions of acceptors, and accordingly, the A/A and D/A intermolecular interactions. The results show that SMA LA17 with low A/A interactions exhibits inferior performance around 12%, owing to its strong D/A interaction with donor PM6, which shapes too miscible morphology and increases charge recombination. Instead, LA16 with strong A/A interactions and moderate D/A interactions delivers improved bulk-heterojunction (BHJ) networks, and therefore, enhances charge transport and diminishes geminate or trap-assisted charge recombination. Consequently, PM6:LA16 records the competitive efficiency of up to 13.74% among the three systems. Therefore, this study deepens the synergistic or balancing effect of the D/A and A/A interactions on BHJ blends for efficient organic solar cells.

Manipulating the Intermolecular Interactions through Side Chain Engineering and Unilateral π‐Bridge Strategy for Efficient Small Molecular Photovoltaic Acceptor

“…Then we calculated the overall photon energy loss ( E loss ) of two devices based on the EQE curves and V OC (Table 3). [ 46,47 ] The PM6:ID‐C6Ph‐4F device gives a relatively high E loss up to 0.74 eV, but still lower than that of PM6:ID‐4F device (as high as 0.92 eV). With the insertion of unilateral π‐bridge, the resulting acceptor ID‐C6Ph‐ST‐4F receives a remarkably reduced E loss of 0.57 eV, even mildly smaller than that of PM6:IDST‐4F (0.59 eV).…”

“…Unexpectedly, despite the smaller HOMO energy offset between PM6 and ID‐C6Ph‐ST‐4F compared to PM6:ID‐C6Ph‐4F system, the greater P diss may be promoted by the larger D/A interactions. [ 47 ] Moreover, we calculated the charge collection efficiencies P coll ( P coll = J max / J sat , where J max represents the current density at maximum output power point) of two devices. As Table S2 (Supporting Information) shows, the PM6:ID‐C6Ph‐ST‐4F based solar cell affords greatly improved P coll up to 89.4% compared to 80.0% of PM6:ID‐C6Ph‐ST‐4F counterpart, which is probably contributed to the better charge transport and suppressed charge recombination loss in BHJ networks.…”

Synergetic Strategy for Highly Efficient and Super Flexible Thick‐film Organic Solar Cells

“…The relationship between J SC and P light can be approximately defined as J SC ∝ P light s , [53,54] and that of V OC and P light can be approximately defined as V OC ∝ nkT/q ln(P light ), where k, T, and q represent Boltzmann constant, Kelvin temperature, and elementary charge, respectively. [55,56] The corresponding s and n are summarized in Figure 4c,d The transient photocurrent and transient photovoltage were also measured to further illustrate the carrier transport and collection of OSCs, as shown in Figure S14, Supporting Information. The fitting carrier lifetime (τ rec ) and charge extraction time (τ ext ) are summarized in Figure 4e,f.…”

High‐Performance Ternary Semitransparent Polymer Solar Cells with Different Bandgap Third Component as Non‐Fullerene Guest Acceptor

“…Semitransparent photovoltaic devices [52][53][54][55] were fabricated based on PM6:Y6:ITIC/IT-4 F/IHIC-based ternary systems under optimal conditions via lowering the thickness of the cathode electrode. Ternary semitransparent strategy [56][57][58] could achieve the trade-off among photovoltaic performance, [59] absorption property, and transmittance. In this work, ST-PSCs were fabricated with a device structure of ITO/ PEDOT:PSS/ PM6:Y6:ITIC/ IT-4 F/IHIC (1.0:1.0:0.2, w/w/w)/ PDINO/ Au (1 nm) and Ag (10/15/20 nm).…”