Microcavity is an efficient approach to manufacture colorful semitransparent organic solar cells (ST-OSCs) with high color purity by tailoring the transmission spectrum to narrow peaks. However, in this type of colorful semitransparent devices, high power conversion efficiency (PCE) and high peak transmittance are not yet simultaneously achieved. This paper proposes a new type of microcavity structure to achieve colorful ST-OSCs with both high PCE and high peak transmittance, in which a hybrid Au/Ag electrode is used as a mirror and WO3 is used as a spacer layer. First, it is demonstrated that the hybrid Au/Ag electrode mirror brings about an improvement of 7.7 and 5.5% for PCE and peak transmittance, respectively, when compared with those of the reference devices using the Ag electrode mirror. Specifically, the PCE of the optimized devices reaches the satisfactory value of over 9%, and the peak transmittance is over 25%. This value of PCE is the highest one reported so far for the microcavity-based ST-OSCs with the same peak transmittance. Second, it is demonstrated that the second-order resonance of the microcavity can be used to improve the color purity of green ST-OSCs by narrowing the transmission peak, and the combination of the second-order and third-order resonance can be used to construct colorful ST-OSCs with mixed colors. Thus, a novel approach is developed to tune the color of ST-OSCs, which is based on high-order resonance modes of the microcavity.

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The current high-performance polymerized small molecular acceptors (PSMAs) are mainly polymerized through terminal groups of small molecular acceptors (SMAs), which will inevitably damage the preferred stackings of terminal groups and render an inferior photoelectric performance of all-polymer solar cells (all-PSCs). In order to liberate terminal groups for more efficient intermolecular stackings, a new pathway to construct PSMAs is explored by extending molecular conjugation in branched directions, thereby affording two PSMAs of SP-T and SP-TT with thiophene and bithiophene as linkers, respectively. Benefiting from more compact/ordered π–π stackings and superior morphology, the SP-T-based all-PSC exhibits facilitated charge generation/transport and suppressed recombination, thus yielding a greatly improved efficiency of 13.54% compared with 9.76% for the SP-TT-based one. Our work not only develops a new type of PSMA featuring much enhanced molecular packings but also demonstrates its great potential for achieving state-of-the-art all-PSCs through the delicate engineering of linkers.

Given the great potential for achieving record breaking organic solar cells (OSCs), newly explored solid additives that could optimize nanoscale morphology of active layers have rapidly gained widespread attention. Herein, a new volatile solid additive 2,5-dichlorothieno[3,2-b]thiophene (TT-Cl) is delicately explored, fully satisfying the design criteria of a planar conjugated skeleton with suitable molecular size, symmetrical geometry, and proper halogenation. When applied in the state-of-the-art OSCs with diverse active layers, the quite high crystallinity of TT-Cl and strong interactions with light-harvesting components lead to optimized molecular crystalline ordering, fibrillar networks, and vertical phase distributions, thus offering a significant performance enhancement. Consequently, PM6:Y6-based binary and ternary OSCs achieved PCEs of 18.20% and 18.95%, respectively. Moreover, PM6:CH23-based binary OSCs presented an outstanding PCE of 18.72%. Our work not only provides a broad-spectrum solid additive to optimize film morphologies powerfully but also manifests great potential for achieving a record-breaking PCE of OSCs.

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