Balancing the Efficiency and Synthetic Accessibility of Organic Solar Cells with Isomeric Acceptor Engineering

Abstract

With the continuous development of organic semiconductor materials and on‐going improvement of device technology, the power conversion efficiencies (PCEs) of organic solar cells (OSCs) have surpassed the threshold of 19%. Now, the low production cost of organic photovoltaic materials and devices have become an imperative demand for its practical application and future commercialization. Herein, the feasibility of simplified synthesis for cost‐effective small‐molecule acceptors via end‐cap isomeric engineering is demonstrated, and two constitutional isomers, BTP‐m‐4Cl and BTP‐o‐4Cl, are synthesized and compared in parallel. These two non‐fullerene acceptors (NFAs) have very similar optoelectronic properties but nonuniform morphological and crystallographic characteristics. Consequently, the OSCs composed of PM6:BTP‐m‐4Cl realize PCE of 17.2%, higher than that of the OSCs with PM6:BTP‐o‐4Cl (≈16%). When ternary OSCs are fabricated with PM6:BTP‐m‐4Cl:BTP‐o‐4Cl, the averaged PCE value reaches 17.95%, presenting outstanding photovoltaic performance. Most excitingly, the figure of merit (FOM) values of PM6:BTP‐m‐4Cl, PM6:BTP‐o‐4Cl, and PM6:BTP‐m‐4Cl:BTP‐o‐4Cl based devices are 0.190, 0.178, and 0.202 respectively. The FOM values of these systems are all among the top ones of the current high‐efficiency OSC systems, revealing high cost‐effectiveness of the two NFAs. This work provides a general but accessible strategy to minimize the efficiency‐cost gap and promises the economic prospects of OSCs.

A Partial Metal Coordination Strategy toward High‐Performance and Cost‐Effective Electron Transporting Layer for Organic Solar Cells

“…We assessed electron mobility through the space-charge-limited current (SCLC) method. [50] Figure 3a displays the current-voltage ( J-V ) characteristics of devices utilizing P2VP and P2VP-Co. For P2VP devices, the electron mobility is measured to be 1.07 Â 10 À4 cm 2 V À1 s À1 . Following the coordination of polymer P2VP with CoCl 2 , this parameter escalates to 4.03 Â 10 À4 cm 2 V À1 s À1 .…”

“…The elucidation of charge extraction and recombination processes in devices is further confirmed through transient photocurrent (TPC) and transient photovoltage (TPV) measurements (Figure 3e-f ). [13,50] TPC provides insights into charge extraction, with charge extraction times measured at 0.29 μs for P2VP devices and 0.25 μs for P2VP-Co devices, as depicted in Figure 3f. Notably, devices utilizing P2VP-Co exhibit a shorter charge extraction time, indicating more effective charge extraction.…”

Rational molecular and device design enables organic solar cells approaching 20% efficiency

“…Considering the excellent efficiency in state-of-the-art binary NFA OSCs, the third component is naturally better not to disturb the excellent morphology of the host binary blend. In this regard, NFAs with smart halogen substitution positions in end groups have high potential to provide similar molecular orientation and excellent miscibility 19 , but adjustable different aggregation and photoelectronic properties. In this sense, the development of such NFAs is likely to achieve the efficiency enhancement goal.…”

Silane or Siloxane‐Side‐Chain Engineering of Photovoltaic Materials for Organic Solar Cells†

“…[1][2][3][4][5][6] With reasonable design of the photovoltaic materials, innovative device fabrication technologies, and a deep understanding of morphology optimization, the power conversion efficiencies (PCEs) of OSCs have been approaching 20%. [7][8][9][10][11][12][13] As a vital component, the photovoltaic layer consists of bi-continuous donors/acceptors interpenetrating network. The characters of these photovoltaic materials such as absorption, energy level, and charge mobility influence the short-circuit current density (J SC ), open circuit voltage (V OC ), and ultimately impact device performance.…”