Constructing tandem and multi‐blend organic solar cells (OSCs) is an effective way to overcome the absorption limitations of conventional single‐junction devices. However, these methods inevitably require tedious multilayer deposition or complicated morphology‐optimization procedures. Herein, sequential deposition is utilized as an effective and simple method to fabricate multicomponent OSCs with a double‐bulk heterojunction (BHJ) structure of the active layer to further improve photovoltaic performance. Two efficient donor‐acceptor pairs, D18‐Cl:BTP‐eC9 and PM6:L8‐BO, are sequentially deposited to form the D18‐Cl:BTP‐eC9/PM6:L8‐BO double‐BHJ active layer. In these double‐BHJ OSCs, light absorption is significantly improved, and optimal morphology is also retained without requiring a more complicated morphology optimization involved in quaternary blends. Compared to the quaternary blend devices, energy loss (Eloss) is also reduced by rationally matching each donor with an appropriate acceptor. Consequently, the power conversion efficiency (PCE) is improved from 18.25% for D18‐Cl:BTP‐eC9 and 18.69% for PM6:L8‐BO based binary blend OSCs to 19.61% for the double‐BHJ OSCs. In contrast, a D18‐Cl:PM6:L8‐BO:BTP‐eC9 quaternary blend of OSCs exhibited a dramatically reduced PCE of 15.83%. These results demonstrate that a double‐BHJ strategy, with a relatively simple processing procedure, can potentially enhance the device performance of OSCs and lead to more widespread use.

A facile strategy was developed here to improve the film quality of nickel‐based hole transporting layer (HTL) for efficient organic solar cell (OSC) applications. To prevent the agglomeration of Ni(NO3)2 during film deposition, acetylacetonate was added into the precursor solution, which led to the formation of an amorphous and glass‐like state. After thermal annealing (TA) treatment, the film‐forming ability could be further improved. The additional UV‐ozone (UVO) treatment continuously improved the film quality and increased the work function and conductivity of such HTL. The resulting TA & UVO modified Ni(NO3)2 & Hacac HTL produced highly efficient organic solar cells with exciting power conversion efficiencies of 18.42 % and 19.02 % for PM6 : BTP‐eC9 and D18 : BTP‐Th devices, respectively, much higher than the control PEDOT : PSS devices.

Noble-metal catalyst is widely-used to synthesize high-efficiency photovoltaic materials. However, expensive catalysts are difficult to remove and the residual catalysts have deleterious effects on photovoltaic performance. In this study, novel efficient non-fullerene acceptors (NFAs) are synthesized via simple nucleophilic substitution without any noble-metal catalyst. An impressive power conversion efficiency (PCE) of 8.91% is obtained using a single triazine-cored NFA, called NAQ-3. To the best of our knowledge, this is the highest PCE for NFAs synthesized via simple nucleophilic substitution or noble-metal-free reactions. Moreover, a delicate four-armed NFA with a bitriazine core, called NAQ-4, is synthesized as an extension example of this synthesis method. Furthermore, the absorption spectra and energy levels of NAQ-3 and NAQ-4 are compared, and the photovoltaic performance, dissociation process and underlying recombination mechanisms of NAQ-3-and NAQ-4-based organic solar cells are analyzed to determine the structure-performance relationship. The results indicate a successful example of high-performance NFAs synthesized via nucleophilic substitution reactions.

A facile strategy was developed here to improve the film quality of nickel‐based hole transporting layer (HTL) for efficient organic solar cell (OSC) applications. To prevent the agglomeration of Ni(NO3)2 during film deposition, acetylacetonate was added into the precursor solution, which led to the formation of an amorphous and glass‐like state. After thermal annealing (TA) treatment, the film‐forming ability could be further improved. The additional UV‐ozone (UVO) treatment continuously improved the film quality and increased the work function and conductivity of such HTL. The resulting TA & UVO modified Ni(NO3)2 & Hacac HTL produced highly efficient organic solar cells with exciting power conversion efficiencies of 18.42 % and 19.02 % for PM6 : BTP‐eC9 and D18 : BTP‐Th devices, respectively, much higher than the control PEDOT : PSS devices.

Additives are extensively explored for improving PEDOT:PSS performances mainly through the removal of excess PSS and as a secondary dopant. In this work, amine‐containing additives are introduced to PEDOT:PSS solutions as processing additives where the interactions to the PSS are anticipated through electrostatic interactions. Such interactions affected solution property where the increased viscosity is found to significantly increase the out‐of‐plane conductivity of the PEDOT:PSS thin films. Organic solar cells adopting these additive‐assisted processed PEDOT:PSS layers as hole transporting layers (HTL) showed the improved device performances that resulted from the reduced series resistance provided by the PEDOT:PSS HTL. A top power conversion efficiency of 18.28% is achieved with para‐phenylenediamine (PPD) additive in the PEDOT:PSS HTL, which is 3.5% higher compared to devices with neat PEDOT:PSS thin film as the HTL.