Regulating Bulk‐Heterojunction Molecular Orientations through Surface Free Energy Control of Hole‐Transporting Layers for High‐Performance Organic Solar Cells

Interface properties are of critical importance for high‐performance bulk‐heterojunction (BHJ) organic solar cells (OSCs). Here, a universal interface approach to tune the surface free energy (γ_S) of hole‐transporting layers (HTLs) in a wide range through introducing poly(styrene sulfonic acid) sodium salts or nickel formate dihydrate into poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is reported. Based on the optimal γ_S of HTLs and thus improved face‐on molecular ordering in BHJs, enhanced fill factor and power conversion efficiencies in both fullerene and nonfullerene OSCs are achieved, which is attributed to the increased charge carrier mobility and sweepout with reduced recombination. It is found that the face‐on orientation‐preferred BHJs (PBDB‐TF:PC₇₁BM, PBDB‐T:PC₇₁BM, and PBDB‐TF:IT‐4F) favor HTLs with higher γ_S while the edge‐on orientation‐preferred BHJs (PDCDT:PC₇₁BM, P3HT:PC₇₁BM and PDCBT:ITIC) are partial to HTLs with lower γ_S. Based on the surface property–morphology–device performance correlations, a suggestion to select a suitable HTL in terms of γ_S for a specific BHJ with favored molecular arrangement is provided. This work enriches the fundamental understandings on the interface characteristics and morphological control toward high‐efficiency OSCs based on a wide range of BHJ materials.     

16.67% Rigid and 14.06% Flexible Organic Solar Cells Enabled by Ternary Heterojunction Strategy

Ternary heterojunction strategies appear to be an efficient approach to improve the efficiency of organic solar cells (OSCs) through harvesting more sunlight. Ternary OSCs are fabricated by employing wide bandgap polymer donor (PM6), narrow bandgap nonfullerene acceptor (Y6), and PC₇₁BM as the third component to tune the light absorption and morphologies of the blend films. A record power conversion efficiency (PCE) of 16.67% (certified as 16.0%) on rigid substrate is achieved in an optimized PM6:Y6:PC₇₁BM blend ratio of 1:1:0.2. The introduction of PC₇₁BM endows the blend with enhanced absorption in the range of 300–500 nm and optimises interpenetrating morphologies to promote photogenerated charge dissociation and extraction. More importantly, a PCE of 14.06% for flexible ITO‐free ternary OSCs is obtained based on this ternary heterojunction system, which is the highest PCE reported for flexible state‐of‐the‐art OSCs. A very promising ternary heterojunction strategy to develop highly efficient rigid and flexible OSCs is presented.     

A General Approach for Lab‐to‐Manufacturing Translation on Flexible Organic Solar Cells

The blossoming of organic solar cells (OSCs) has triggered enormous commercial applications, due to their high‐efficiency, light weight, and flexibility. However, the lab‐to‐manufacturing translation of the praisable performance from lab‐scale devices to industrial‐scale modules is still the Achilles' heel of OSCs. In fact, it is urgent to explore the mechanism of morphological evolution in the bulk heterojunction (BHJ) with different coating/printing methods. Here, a general approach to upscale flexible organic photovoltaics to module scale without obvious efficiency loss is demonstrated. The shear impulse during the coating/printing process is first applied to control the morphology evolution of the BHJ layer for both fullerene and nonfullerene acceptor systems. A quantitative transformation factor of shear impulse between slot‐die printing and spin‐coating is detected. Compelling results of morphological evolution, molecular stacking, and coarse‐grained molecular simulation verify the validity of the impulse translation. Accordingly, the efficiency of flexible devices via slot‐die printing achieves 9.10% for PTB7‐Th:PC₇₁BM and 9.77% for PBDB‐T:ITIC based on 1.04 cm² . Furthermore, 15 cm² flexible modules with effective efficiency up to 7.58% (PTB7‐Th:PC₇₁BM) and 8.90% (PBDB‐T:ITIC) are demonstrated with satisfying mechanical flexibility and operating stability. More importantly, this work outlines the shear impulse translation for organic printing electronics.     

Photovoltaic contribution of photo-generated excitons in acceptor material of organic solar cells

Contribution of exciton generation in acceptor material to the photovoltaic performance of three bulk-heterojunction organic solar cells (BHJ OSCs), PTB7:PC₇₁BM, P3HT:ICBA and P3HT:PC₆₁BM are studied. Singlet and triplet rates of absorption and dissociation and diffusion lengths are calculated and compared with those when excitons are generated in the donor of these BHJ OSCs. It is found that the rates of absorption and dissociation and diffusion lengths are comparable whether excitons are generated in donor or acceptor of these BHJ OSCs. Therefore, it is proposed that the contribution of exciton generation in acceptor may not be negligible.     

Semiconducting Carbon Nanotube Aerogel Bulk Heterojunction Solar Cells

Using a novel two‐step fabrication scheme, we create highly semiconducting‐enriched single‐walled carbon nanotube (sSWNT) bulk heterojunctions (BHJs) by first creating highly porous interconnected sSWNT aerogels (sSWNT‐AEROs), followed by back‐filling the pores with [6,6]‐phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM). We demonstrate sSWNT‐AERO structures with density as low as 2.5 mg cm^?3, porosity as high as 99.8%, and diameter of sSWNT fibers ≤10 nm. Upon spin coating with PC₇₁BM, the resulting sSWNT‐AERO‐PC₇₁BM nanocomposites exhibit highly quenched sSWNT photoluminescence, which is attributed to the large interfacial area between the sSWNT and PC₇₁BM phases, and an appropriate sSWNT fiber diameter that matches the inter‐sSWNT exciton migration length. Employing the sSWNT‐AERO‐PC₇₁BM BHJ structure, we report optimized solar cells with a power conversion efficiency of 1.7%, which is exceptional among polymer‐like solar cells in which sSWNTs are designed to replace either the polymer or fullerene component. A fairly balanced photocurrent is achieved with 36% peak external quantum efficiency (EQE) in the visible and 19% peak EQE in the near‐infrared where sSWNTs serve as electron donors and photoabsorbers. Our results prove the effectiveness of this new method in controlling the sSWNT morphology in BHJ structures, suggesting a promising route towards highly efficient sSWNT photoabsorbing solar cells.     

Impact of Solvent Additive on Carrier Transport in Polymer:Fullerene Bulk Heterojunction Photovoltaic Cells

The effects of a solvent additive, 1,8‐diiodooctane (DIO), on both hole and electron transport are investigated in a state‐of‐the‐art bulk‐heterojunction (BHJ) system, namely PTB7:PC₇₁BM. For a polymer:fullerene weight ratio of 1:1.5, the electron mobility in the blend film increases by two orders of magnitude with the DIO concentration while almost no change is found in the hole mobility. For lower DIO concentrations, the electron mobility is suppressed because of large, but poorly connected PC₇₁BM domains. For higher concentrations of DIO, the electron mobility is improved progressively and the hole mobility becomes the limiting factor. Between 1 and 5 vol%, the electron and hole mobilities are balanced. Using the Gaussian disorder model (GDM), we found that the DIO concentration modifies fundamentally the average hopping distances of the electrons. In addition, there exist alternative donor–acceptor ratios to achieve optimized PTB7:PC₇₁BM based solar cells. It is demonstrated that the fullerene content of the BHJ film can be significantly reduced from 1:1.5 to 1:1 while the optimized performance can still be preserved.     

Single‐Junction Binary‐Blend Nonfullerene Polymer Solar Cells with 12.1% Efficiency

A new fluorinated nonfullerene acceptor, ITIC‐Th1, has been designed and synthesized by introducing fluorine (F) atoms onto the end‐capping group 1,1‐dicyanomethylene‐3‐indanone (IC). On the one hand, incorporation of F would improve intramolecular interaction, enhance the push–pull effect between the donor unit indacenodithieno[3,2‐b]thiophene and the acceptor unit IC due to electron‐withdrawing effect of F, and finally adjust energy levels and reduce bandgap, which is beneficial to light harvesting and enhancing short‐circuit current density (J _SC). On the other hand, incorporation of F would improve intermolecular interactions through C? F···S, C? F···H, and C? F···π noncovalent interactions and enhance electron mobility, which is beneficial to enhancing J _SC and fill factor. Indeed, the results show that fluorinated ITIC‐Th1 exhibits redshifted absorption, smaller optical bandgap, and higher electron mobility than the nonfluorinated ITIC‐Th. Furthermore, nonfullerene organic solar cells (OSCs) based on fluorinated ITIC‐Th1 electron acceptor and a wide‐bandgap polymer donor FTAZ based on benzodithiophene and benzotriazole exhibit power conversion efficiency (PCE) as high as 12.1%, significantly higher than that of nonfluorinated ITIC‐Th (8.88%). The PCE of 12.1% is the highest in fullerene and nonfullerene‐based single‐junction binary‐blend OSCs. Moreover, the OSCs based on FTAZ:ITIC‐Th1 show much better efficiency and better stability than the control devices based on FTAZ:PC₇₁BM (PCE = 5.22%).     

Efficient bulk heterojunction solar cells based on D–A copolymers as electron donors and PC70BM as electron acceptor

Two low band gap conjugated polymers P1 (alternating phenylenevinylene containing thiophene and pyrrole rings) and P2 (alternating phenylenevinylene with dithenyl (thienothiadiazole) segments) having optical band gap 1.65 eV and 1.74 eV, respectively, were used as electron donor along with the PC₇₀BM as electron acceptor for the fabrication of bulk heterojunction solar cells. The power conversion efficiency (PCE) of BHJ devices based on P1:PC₇₀BM and P2:PC₇₀BM cast from THF solvent is about 2.84% and 2.34%, respectively, which is higher than the BHJ based on PCBM as electron acceptor. We have investigated the effect of mixed (1-chloronaphthalene (CN)/THF) solvent, modification of PEDOT:PSS layer and inserting of TiO₂ layer, on the photovoltaic performance of polymer solar cell. We have achieved power conversion efficiency of 5.07% for the polymer solar cells having structure ITO/PEDOT:PSS (modified)/P1:PC₇₀BM (CN/THF cast)/TiO₂/Al. The effect of solvent used for spin coating, modification of PEDOT:PSS layer and inclusion of TiO₂ layer has been discussed in detail.     

Superiority of branched side chains in spontaneous nanowire formation: exemplified by poly(3-2-methylbutylthiophene) for high-performance solar cells

One‐dimensional nanostructures containing heterojunctions by conjugated polymers, such as nanowires, are expected to greatly facilitate efficient charge transfer in bulk‐heterojunction (BHJ) solar cells. Thus, a combined theoretical and experimental approach is pursued to explore spontaneous nanowire formation. A dissipative particle dynamics simulation is first performed to study the morphologies formed by rodlike polymers with various side‐chain structures. The results surprisingly predict that conjugated polymers with branched side chains are well suited to form thermodynamically stable nanowires. Proof of this concept is provided via the design and synthesis of a branched polymer of regioregular poly(3‐2‐methylbutylthiophene) (P3MBT), which successfully demonstrates highly dense nanowire formation free from any stringent conditions and stratagies. In BHJ solar cells fabricated using a blend of P3MBT and [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC₇₁BM), P3MBT polymers are self‐organized into highly crystalline nanowires with a d₁₀₀ spacing of 13.30 Å. The hole mobility of the P3MBT:PC₇₁BM (1:0.5 by weight) blend film reaches 3.83 × 10^?4 cm² V^?1 s^?1, and the maximum incident photon‐to‐current efficiency reaches 68%. The results unambiguously prove the spontaneous formation of nanowires using solution‐processable conjugated polymers with branched alkyl side chains in BHJ solar cells.     

Investigation of structural, optical, and electrical properties of regioregular poly(3-hexylthiophene)/fullerene blend nanocomposites for organic solar cells

We investigated the influence of thermal annealing on the structural and optical properties of two variations of organic nanocomposite materials; 1) poly [3-hexylthiophene] and [6,6]-phenyl C₆₁ butyric acid methyl ester ( P3HT:PC₆₁BM), and 2) poly [3-hexylthiophene] and [6,6]-phenyl C₇₁ butyric acid methyl ester) (P3HT:PC₇₁BM). The evolution of surface roughness and morphology was investigated using atomic force microscopy while device electrical properties were investigated by measuring current-voltage (I-V) characteristics. Upon thermal treatment, results show that P3HT:PC₇₁BM nanocomposites produce a more homogeneous mixture of finer grain size than P3HT:PC₆₁BM. Furthermore, stronger optical absorption in the visible region is observed in P3HT:PC₇₁BM compared to P3HT:PC₆₁BM. Since optical absorption is closely related to film crystallinity, it is inferred that P3HT:PC₇₁BM composites undergo more extensive crystallization upon annealing. Photoluminescence spectra of both P3HT:PC₆₁BM and P3HT:PC₇₁BM nanocomposites (dissolved in chlorobenzene) show that each has excellent quenching effects. I-V characteristic curves show that P3HT:PC₇₁BM registers higher current density under AM 1.5 illumination than does P3HT:PC₆₁BM. For the devices described in this paper having active areas of approximately 12 mm², efficiency is approximately 33% better for C₇₁-based solar cells than that observed for devices made using C₆₁ fullerene.     

Directed Vertical Diffusion of Photovoltaic Active Layer Components into Porous ZnO‐Based Cathode Buffer Layers

Cathode buffer layers (CBLs) can effectively further the efficiency of polymer solar cells (PSCs), after optimization of the active layer. Hidden between the active layer and cathode of the inverted PSC device configuration is the critical yet often unattended vertical diffusion of the active layer components across CBL. Here, a novel methodology of contrast variation with neutron and anomalous X‐ray reflectivity to map the multicomponent depth compositions of inverted PSCs, covering from the active layer surface down to the bottom of the ZnO‐based CBL, is developed. Uniquely revealed for a high‐performance model PSC are the often overlooked porosity distributions of the ZnO‐based CBL and the differential diffusions of the polymer PTB7‐Th and fullerene derivative PC₇₁BM of the active layer into the CBL. Interface modification of the ZnO‐based CBL with fullerene derivative PCBE? OH for size‐selective nanochannels can selectively improve the diffusion of PC₇₁BM more than that of the polymer. The deeper penetration of PC₇₁BM establishes a gradient distribution of fullerene derivatives over the ZnO/PCBE‐OH CBL, resulting in markedly improved electron mobility and device efficiency of the inverted PSC. The result suggests a new CBL design concept of progressive matching of the conduction bands.     

Efficiency enhancement in DIBSQ:PC<Subscript>71</Subscript>BM organic photovoltaic cells by using Liq-doped Bphen as a cathode buffer layer

We have improved the photovoltaic performance of 2,4-bis[4-(N,Ndiisobutylamino)- 2,6-dihydroxyphenyl] squaraine:[6,6]-phenyl C71-butyric acid methyl ester (DIBSQ:PC₇₁BM) organic photovoltaic (OPV) cells via incorporating Liq-doped Bphen (Bphen-Liq) as a cathode buffer layer (CBL). Based on the Bphen-Liq CBL, a DIBSQ:PC₇₁BM OPV cell possessed an optimal power conversion efficiency of 4.90%, which was 13% and 60% higher than those of the devices with neat Bphen as CBL and without CBL, respectively. The enhancement of the device performance could be attributed to the enhanced electron mobility and improved electrode/active layer contact and thus the improved photocurrent extraction by incorporating the Bphen-Liq CBL. Light-intensity dependent device performance analysis indicates that the incorporating of the Bphen-Liq CBL can remarkably improve the charge transport of the DIBSQ:PC₇₁BM OPV cell and thus decrease the recombination losses of the device, resulting in enhanced device performance. Our finding indicates that the doped Bphen-Liq CBL has great potential for high-performance solution-processed small-molecule OPVs.     

Highly Efficient Ternary‐Blend Polymer Solar Cells Enabled by a Nonfullerene Acceptor and Two Polymer Donors with a Broad Composition Tolerance

In this work, highly efficient ternary‐blend organic solar cells (TB‐OSCs) are reported based on a low‐bandgap copolymer of PTB7‐Th, a medium‐bandgap copolymer of PBDB‐T, and a wide‐bandgap small molecule of SFBRCN. The ternary‐blend layer exhibits a good complementary absorption in the range of 300–800 nm, in which PTB7‐Th and PBDB‐T have excellent miscibility with each other and a desirable phase separation with SFBRCN. In such devices, there exist multiple energy transfer pathways from PBDB‐T to PTB7‐Th, and from SFBRCN to the above two polymer donors. The hole‐back transfer from PTB7‐Th to PBDB‐T and multiple electron transfers between the acceptor and the donor materials are also observed for elevating the whole device performance. After systematically optimizing the weight ratio of PBDB‐T:PTB7‐Th:SFBRCN, a champion power conversion efficiency (PCE) of 12.27% is finally achieved with an open‐circuit voltage (V _oc) of 0.93 V, a short‐circuit current density (J _sc) of 17.86 mA cm^?2, and a fill factor of 73.9%, which is the highest value for the ternary OSCs reported so far. Importantly, the TB‐OSCs exhibit a broad composition tolerance with a high PCE over 10% throughout the whole blend ratios.     

Improved Domain Size and Purity Enables Efficient All‐Small‐Molecule Ternary Solar Cells

An all‐small‐molecule ternary solar cell is achieved with a power conversion efficiency of 10.48% by incorporating phenyl‐C₇₁‐butyric‐acid‐methyl ester (PC₇₁BM) into a nonfullerene binary system. The addition of PC₇₁BM is found to modulate the film morphology by improving the domain purity and decreasing the domain size. This modulation facilitates charge generation and suppresses charge recombination, as manifested by the significantly enhanced short‐circuit current density and fill factor. The results correlate the domain characteristics with the device performance and offer new insight from the perspective of morphology modulation for constructing efficient ternary devices.     

An Efficient, “Burn in” Free Organic Solar Cell Employing a Nonfullerene Electron Acceptor

A comparison of the efficiency, stability, and photophysics of organic solar cells employing poly[(5,6‐difluoro‐2,1,3‐benzothiadiazol‐4,7‐diyl)‐alt‐(3,3′″‐di(2‐octyldodecyl)‐2,2′;5′,2″;5″,2′″‐quaterthiophen‐5,5′″‐diyl)] (PffBT4T‐2OD) as a donor polymer blended with either the nonfullerene acceptor EH‐IDTBR or the fullerene derivative, [6,6]‐phenyl C₇₁ butyric acid methyl ester (PC₇₁BM) as electron acceptors is reported. Inverted PffBT4T‐2OD:EH‐IDTBR blend solar cell fabricated without any processing additive achieves power conversion efficiencies (PCEs) of 9.5 ± 0.2%. The devices exhibit a high open circuit voltage of 1.08 ± 0.01 V, attributed to the high lowest unoccupied molecular orbital (LUMO) level of EH‐IDTBR. Photoluminescence quenching and transient absorption data are employed to elucidate the ultrafast kinetics and efficiencies of charge separation in both blends, with PffBT4T‐2OD exciton diffusion kinetics within polymer domains, and geminate recombination losses following exciton separation being identified as key factors determining the efficiency of photocurrent generation. Remarkably, while encapsulated PffBT4T‐2OD:PC₇₁BM solar cells show significant efficiency loss under simulated solar irradiation (“burn in” degradation) due to the trap‐assisted recombination through increased photoinduced trap states, PffBT4T‐2OD:EH‐IDTBR solar cell shows negligible burn in efficiency loss. Furthermore, PffBT4T‐2OD:EH‐IDTBR solar cells are found to be substantially more stable under 85 °C thermal stress than PffBT4T‐2OD:PC₇₁BM devices.     

Morphological studies of small-molecule solar cells: nanostructural engineering via solvent vapor annealing treatments

Fine-tuning nano/micro-structural morphologies and their depth studies in small-molecule solar cells are key parameters in elevating device performances. In the current work, we focused on controlling the morphology of a small-molecule organic photovoltaic by treating its active layer film with solvent vapor annealing (SVA). For this project, the devices were made of all-small-molecule p-DTS(FBTTh₂)₂:PC₇₁BM heterojunction films processed using different solvents for the vapor annealing. The different solvents resulted in different nano-domain packing structures and segregated phase separation as evidenced by detailed two-dimensional grazing-incidence wide-angle X-ray scattering (2D-GIWAXS) and atomic force microscopy (AFM) analyses. From the data, we demonstrated a correlation between the nanostructural morphology of the active layer film and the performance of the device and found an SVA condition that produced a p-DTS(FBTTh₂)₂:PC₇₁BM blend system yielding an improved device performance.     

Recent Progress in Molecular Design of Fused Ring Electron Acceptors for Organic Solar Cells

The quest for sustainable energy sources has led to accelerated growth in research of organic solar cells (OSCs). A solution‐processed bulk‐heterojunction (BHJ) OSC generally contains a donor and expensive fullerene acceptors (FAs). The last 20 years have been devoted by the OSC community to developing donor materials, specifically low bandgap polymers, to complement FAs in BHJs. The current improvement from ≈2.5% in 2013 to 17.3% in 2018 in OSC performance is primarily credited to novel nonfullerene acceptors (NFA), especially fused ring electron acceptors (FREAs). FREAs offer unique advantages over FAs, like broad absorption of solar radiation, and they can be extensively chemically manipulated to tune optoelectronic and morphological properties. Herein, the current status in FREA‐based OSCs is summarized, such as design strategies for both wide and narrow bandgap FREAs for BHJ, all‐small‐molecule OSCs, semi‐transparent OSC, ternary, and tandem solar cells. The photovoltaics parameters for FREAs are summarized and discussed. The focus is on the various FREA structures and their role in optical and morphological tuning. Besides, the advantages and drawbacks of both FAs and NFAs are discussed. Finally, an outlook in the field of FREA‐OSCs for future material design and challenges ahead is provided.     

Unraveling the Role of Substrates on Interface Energetics and Morphology of PCDTBT:PC70BM Bulk Heterojunction

In the pursuit of developing highly efficient polymer solar cells, it is indispensable to experimentally determine the molecular electronic and geometrical structures of distributed donor/acceptor bulk heterojunctions for understanding the processes inside the cell. In this article, substrate effect on interface energetics and film morphology of the poly[N‐9′‐heptadecanyl‐2,7‐carbazole‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole)]:[6,6]‐phenyl‐C₇₀ butyric acid methyl ester (PCDTBT:PC₇₀BM) blends with various blending ratios on various conductive substrates is clarified based on the characterization of photoelectron spectroscopy and atomic force microscope, where the PCDTBT:PC₇₀BM blend film serves as an important model system due to efficient charge generation and transport with low recombination. The energetics of the PCDTBT:PC₇₀BM blend film is demonstrated to be highly dependent on the substrate work function, showing the transition from vacuum level alignment to Fermi level pinning with the variation of PC₇₀BM ratio in the blend film. The resulting morphology is in good agreement with the observed formation of a PCDTBT‐rich layer at the top of the PCDTBT:PC₇₀BM blend film irrespective of the variation of the PC₇₀BM blending ratio and annealing temperature. The results show the possibility of tuning the interfacial electronic structures by utilizing the substrate effects and potential applications on performance enhancement in polymer solar cells.     

Improvement of organic solar cell efficiency by solution-processed doping of pentacene in PEDOT:PSS layer

In the current research, organic solar cells (OSCs) with various concentrations of pentacene in Poly(ethylenedioxythiopene):Poly(styrenesulfonate) (PEDOT:PSS) interface layer were investigated for better hole extraction. The ITO/Pentacene?+?PEDOT:PSS/P3HT:PCBM/Al-fabricated solar cell fabricated via brush coating provides superior photovoltaic, electrical and optical characteristics when compared with the ITO/PEDOT:PSS/P3HT:PCBM/Al solar cell. The ITO/Pentacene?+?PEDOT:PSS/P3HT:PCBM/Al solar cells deliver a V_OC ~350?mV and 2.57% efficiency. It is observed that the optimized concentration of pentacene doping in PEDOT:PSS layer, along with an active layer of P3HT and PC₆₀BM, doubles the efficiency of the device, when compared with pristine PEDOT:PSS layer. The degradation studies of the fabricated bulk heterojunction OSCs reveal that the degrading abilities of ITO/Pentacene?+?PEDOT:PSS/P3HT:PCBM/Al solar cells are 60% more better than those of ITO/PEDOT:PSS/P3HT:PCBM/Al devices. Thus, this work will ultimately contribute toward fully solution processed painted device, which will provide low-cost manufacturing and improved stability of pentacene-based organic photovoltaics.     

Air‐Processed,Stable Organic Solar Cells with High Power Conversion Efficiency of 7.41%

High efficiency, excellent stability, and air processability are all important factors to consider in endeavoring to push forward the real‐world application of organic solar cells. Herein, an air‐processed inverted photovoltaic device built upon a low‐bandgap, air‐stable, phenanthridinone‐based ter‐polymer (C₁₅₀H₂₁₈N₆O₆S₄)_n (PDPPPTD) and [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PC₆₁BM) without involving any additive engineering processes yields a high efficiency of 6.34%. The PDPPPTD/PC₆₁BM devices also exhibit superior thermal stability and photo‐stability as well as long‐term stability in ambient atmosphere without any device encapsulation, which show less performance decay as compared to most of the reported organic solar cells. In view of their great potential, solvent additive engineering via adding p‐anisaldehyde (AA) is attempted, leading to a further improved efficiency of 7.41%, one of the highest efficiencies for all air‐processed and stable organic photovoltaic devices. Moreover, the device stability under different ambient conditions is also further improved with the AA additive engineering. Various characterizations are conducted to probe the structural, morphology, and chemical information in order to correlate the structure with photovoltaic performance. This work paves a way for developing a new generation of air‐processable organic solar cells for possible commercial application.