Inhibiting excessive molecular aggregation to achieve highly efficient and stabilized organic solar cells by introducing a star-shaped nitrogen heterocyclic-ring acceptor

Abstract

Inhibiting excessive aggregation and migration of active layer molecules is essential to improve the stability and performance of organic solar cells (OSCs). Herein, the star-shaped nitrogen heterocyclic-ring acceptor TF1 featuring...

Layer‐by‐Layer Processed PM6:Y6‐Based Stable Ternary Polymer Solar Cells with Improved Efficiency over 18% by Incorporating an Asymmetric Thieno[3,2‐b]indole‐Based Acceptor

“…It was well known that the good miscibility between two different acceptors was considered to be an essential prerequisite for the formation of the alloying acceptor. [ 32 ] As a consequence, the contact angles measurement of PM6, Y6, and TIT‐2Cl films were performed and presented in Figure 1f and Table S2, Supporting Information. The similar surface energy (γ) of Y6 and TIT‐2Cl (24.53 mN m −1 for Y6 and 26.53 mN m −1 for TIT‐2Cl) indicated the good miscibility between Y6 and TIT‐2Cl.…”

“…Significantly, it is clearly seen that the V OC of BHJ‐type and LBL‐type ternary PSCs increases gradually with the increase of TIT‐2Cl ratios ( Table 1 and Table S7, Supporting Information), which mainly results from the formation of an alloy state between the TIT‐2Cl and Y6 accompanied by the addition of TIT‐2Cl. [ 32 ] To deeply confirm the formation of the alloyed acceptor between the two different acceptors, the energy level of TIT‐2Cl:Y6 was obtained from the CV measurement (Figure S3, Supporting Information). The LUMO level of TIT‐2Cl:Y6 was −3.96 eV, which was lower than that of TIT‐2Cl (−3.91 eV) and also higher than that of Y6 (4.02 eV), suggesting that the alloy state might be formed between TIT‐2Cl and Y6.…”

“…[21,[26][27][28][29][30] Sometimes, due to the strong intermolecular interaction between the third guest and host donor (or host acceptor), it could cause excessive aggregation in the PM6:Y6 system (especially for the Y6 with unique 3D stacking structure, [31] and thus serious over-aggregation phenomenon often occurs in Y6-based system), and thus leading to the poor long-term stability of the devices. [32] In consequence, it is urgent to develop a novel material or device optimization method that can not only enhance the PCE of PSCs but also maintain long-term stability of morphology.…”

“…[37,38] To realize vertical phase separation, a layer-by-layer (LBL) spin-coating means was designed to form a P-i-N-type device structure (as shown in Figure 1d) by sequentially depositing donor layer and acceptor layer. [32,[38][39][40][41][42][43][44][45][46][47][48] For instance, Min et al prepared the LBL-type device using the blade-coating method by inserting the PM6 layer below the Y6 layer. Compared with the BHJ-type device, the LBL-type device has the advantages of P-i-N-type morphology control, good charge transfer, and extraction performance, and thus displayed a higher PCE of 16.35%.…”

Green‐Solvent‐Processed 17% Efficient Polymer Solar Cell Achieved Synergistically by Aligning Energy Levels and Improving Morphology with the Quaternary Strategy

“…To address this issue, we proposed the "voltage-increased" ternary approach in which increased device V OC values were obtained in combination with improved FFs, in general, by employing a higher-LUMO acceptor guest. [26,[49][50][51][52][53][54] However, increased J SC values were rarely observed when using nonfullerene small-molecule acceptor guests. In contrast, employing narrowed optical bandgap acceptor guests, increased J SC could be obtained, while decreased V OC values were generally observed.…”