Performance Enhancement of Polymer‐Free Carbon Nanotube Solar Cells via Transfer Matrix Modeling

Polymer‐free (6,5) single‐walled carbon nanotubes (SWCNTs) prepared using the gel permeation approach are integrated into SWCNT:C₆₀ solar cells. Evaporation‐driven self‐assembly is used to form large‐area SWCNT thin films from the surfactant‐stabilized aqueous suspensions. The thicknesses of various layers within the solar cell are optimized by theoretical modeling using transfer matrix calculations, where the distribution of the electric field within the stack is matched to light absorption by the SWCNTs through either their primary (S₁₁) or secondary (S₂₂) absorption peaks, or a combination thereof. The validity of the model is verified experimentally through a detailed parameter study and then used to develop SWCNT:C₆₀ solar cells with high open‐circuit voltage (0.44 V) as well as a cutting‐edge internal quantum efficiency of up to 86% through the nanotube S₁₁ transition, over an active area of 0.105 cm².     

Absence of Charge Transfer State Enables Very Low VOC Losses in SWCNT:Fullerene Solar Cells

Current state‐of‐the‐art organic solar cells (OSCs) still suffer from high losses of open‐circuit voltage (V_OC). Conventional polymer:fullerene solar cells usually exhibit bandgap to V_OC losses greater than 0.8 V. Here a detailed investigation of V_OC is presented for solution‐processed OSCs based on (6,5) single‐walled carbon nanotube (SWCNT): [6,6]‐phenyl‐C₇₁‐butyric acid methyl ester active layers. Considering the very small optical bandgap of only 1.22 eV of (6,5) SWCNTs, a high V_OC of 0.59 V leading to a low E_gap/q ? V_OC = 0.63 V loss is observed. The low voltage losses are partly due to the lack of a measurable charge transfer state and partly due to the narrow absorption edge of SWCNTs. Consequently, V_OC losses attributed to a broadening of the band edge are very small, resulting in V_OC,SQ ? V_OC,rad = 0.12 V. Interestingly, this loss is mainly caused by minor amounts of SWCNTs with smaller bandgaps as well as (6,5) SWCNT trions, all of which are experimentally well resolved employing Fourier transform photocurrent spectroscopy. In addition, the low losses due to band edge broadening, a very low voltage loss are also found due to nonradiative recombination, ΔV_OC,nonrad = 0.26 V, which is exceptional for fullerene‐based OSCs.     

Enhanced Uniformity and Area Scaling in Carbon Nanotube–Fullerene Bulk‐Heterojunction Solar Cells Enabled by Solvent Additives

Single‐walled carbon nanotube (SWCNT) fullerene solar cells have recently attracted attention due to their low‐cost processing, high environmental stability, and near‐infrared absorption. While SWCNT–fullerene bulk‐heterojunction photovoltaics employing an inverted architecture and polychiral SWCNTs have achieved efficiencies exceeding 3% over device areas of ≈1 mm², large‐area SWCNT solar cells have not yet been demonstrated. In particular, with increasing device area, spatial inhomogeneities in the SWCNT film have limited overall device performance. Here, 1,8‐diiodooctane (DIO) is utilized as a solvent additive to reduce fullerene domain size and to improve SWCNT–fullerene bulk‐heterojunction morphology. Under optimized conditions, DIO elucidates the influence of SWCNT chiral distribution on overall device performance, revealing a tradeoff between short‐circuit current density and fill factor as a function of the chirality distribution present. The combination of SWCNT chirality distribution engineering and improved spatial homogeneity via solvent additives enables area‐scaling of SWCNT–fullerene solar cells with performance comparable to small‐area cells.     

Record Open‐Circuit Voltage Wide‐Bandgap Perovskite Solar Cells Utilizing 2D/3D Perovskite Heterostructure

In this work, the authors realize stable and highly efficient wide‐bandgap perovskite solar cells that promise high power conversion efficiencies (PCE) and are likely to play a key role in next generation multi‐junction photovoltaics (PV). This work reports on wide‐bandgap (≈1.72 eV) perovskite solar cells exhibiting stable PCEs of up to 19.4% and a remarkably high open‐circuit voltage (V_OC) of 1.31 V. The V_OC‐to‐bandgap ratio is the highest reported for wide‐bandgap organic?inorganic hybrid perovskite solar cells and the V_OC also exceeds 90% of the theoretical maximum, defined by the Shockley–Queisser limit. This advance is based on creating a hybrid 2D/3D perovskite heterostructure. By spin coating n‐butylammonium bromide on the double‐cation perovskite absorber layer, a thin 2D Ruddlesden–Popper perovskite layer of intermediate phases is formed, which mitigates nonradiative recombination in the perovskite absorber layer. As a result, V_OC is enhanced by 80 mV.     

Multifunctional Effect of p‐Doping,Antireflection, and Encapsulation by Polymeric Acid for High Efficiency and Stable Carbon Nanotube‐Based Silicon Solar Cells

Silicon solar cells among different types of solar energy harvesters have entered the commercial market owing to their high power conversion efficiency and stability. By replacing the electrode and the p‐type layer by a single layer of carbon nanotubes, the device can be further simplified. This greatly augments the attractiveness of silicon solar cells in the light of raw material shortages and the solar payback period, as well as lowering the fabrication costs. However, carbon nanotube‐based silicon solar cells still lack device efficiency and stability. These can be improved by chemical doping, antireflection coating, and encapsulation. In this work, the multifunctional effects of p‐doping, antireflection, and encapsulation are observed simultaneously, by applying a polymeric acid. This method increases the power conversion efficiency of single‐walled carbon nanotube‐based silicon solar cells from 9.5% to 14.4% and leads to unprecedented device stability of more than 120 d under severe conditions. In addition, the polymeric acid‐applied carbon nanotube‐based silicon solar cells show excellent chemical and mechanical robustness. The obtained stable efficiency stands the highest among the reported carbon nanotube‐based silicon solar cells.     

Overcoming Interfacial Losses in Solution‐Processed Organic Multi‐Junction Solar Cells

Organic solar cells are promising in terms of full‐solution‐processing which enables low‐cost and large‐scale fabrication. While single‐junction solar cells have seen a boost in power conversion efficiency (PCE), multi‐junction solar cells are promising to further enhance the PCE. In all‐solution‐processed multi‐junction solar cells, interfacial losses are often encountered between hole‐transporting layer (HTL) and the active layers and therefore greatly limit the application of newly developed high‐performance donor and acceptor materials in multi‐junction solar cells. Here, the authors report on a systematic study of interface losses in both single‐junction and multi‐junction solar cells based on representative polymer donors and HTLs using electron spectroscopy and time‐of‐flight secondary ion mass spectrometry. It is found that a facile mixed HTL containing poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and MoO _x nanoparticles successfully overcomes the interfacial losses in both single‐ and multi‐junction solar cells based on various active layers by reducing interface protonation, promoting better energy‐level alignment, and forming a dense and smooth layer. Solution‐processed single‐junction solar cells are demonstrated to reach the same performance as with evaporated MoO _x (over 7%). Multi‐junction solar cells with polymers containing nitrogen atoms as the first layer and the mixed PEDOT:PSS and MoO _x nanoparticles as hole extraction layer reach fill factor (FF) of over 60%, and PCE of over 8%, while the identical stack with pristine PEDOT:PSS or MoO _x nanoparticles show FF smaller than 50% and PCE less than 5%.     

A Supramolecular “Double‐Cable” Structure with a 12944 Helix in a Columnar Porphyrin‐C60 Dyad and its Application in Polymer Solar Cells

A novel porphyrin‐C₆₀ dyad (PCD1) is designed and synthesized to investigate and manipulate the supramolecular structure where geometrically isotropic [such as [60]fullerene (C₆₀)] and anisotropic [such as porphyrin (Por)] units coexist. It is observed that PCD1 possesses an enantiomeric phase behavior. The melting temperature of the stable PCD1 thermotropic phase is 160 °C with a latent heat (ΔH) of 18.5 kJ mol^?1. The phase formation is majorly driven by the cooperative intermolecular Por–Por and C₆₀–C₆₀ interactions. Structural analysis reveals that this stable phase possesses a supramolecular “double‐cable” structure with one p‐type Por core columnar channel and three helical n‐type C₆₀ peripheral channels. These “double‐cable” columns further pack into a hexagonal lattice with a = b = 4.65 nm, c = 41.3 nm, α = β = 90°, and γ = 120°. The column repeat unit is determined to possess a 129₄₄ helix. With both donor (D; Pro) and acceptor (A; C₆₀) units having their own connecting channels as well as the large D/A interface within the supramolecular “double‐cable” structure, PCD1 has photogenerated carriers with longer lifetimes compared to the conventional electron acceptor [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester. A phase‐separated columnar morphology is observed in a bulk‐heterojunction (BHJ) material made by the physical blend of a low band‐gap conjugated polymer, [poly[2,6‐(4,4‐bis‐(2‐ethylhexyl)‐4H‐cyclopenta [2,1‐b;3,4‐b′]‐dithiophene)‐alt‐4,7‐(2,1,3‐benzothia‐diazole)] (PCPDTBT), and PCD1. With a specific phase structure in the solid state and in the blend, PCD1 is shown to be a promising candidate as a new electron acceptor in high performance BHJ polymer solar cells.     

Influence of Fullerene Acceptor on the Performance,Microstructure, and Photophysics of Low Bandgap Polymer Solar Cells

The morphology, photophysics, and device performance of solar cells based on the low bandgap polymer poly[[2,6′‐4,8‐di(5‐ethylhexylthienyl)benzo[1,2‐b;3,3‐b]dithiophene]3‐fluoro‐2[(2‐ethylhexyl)carbonyl]thieno[3,4‐b]thiophenediyl (PBDTTT‐EFT) (also known as PTB7‐Th) blended with different fullerene acceptors: Phenyl‐C₆₁‐butyric acid methyl ester (PC₆₁BM), phenyl‐C₇₁ ‐butyric acid methyl ester (PC₇₁BM), or indene‐C₆₀ bisadduct (ICBA) are correlated. Compared to PC₇₁ BM‐based cells – which achieve a power conversion efficiency (PCE) of 9.4% – cells using ICBA achieve a higher open‐circuit voltage (V_OC) of 1.0 V albeit with a lower PCE of 7.1%. To understand the origin of this lower PCE, the morphology and photophysics have been thoroughly characterized. Hard and soft X‐ray scattering measurements reveal that the PBDTTT‐EFT:ICBA blend has a lower crystallinity, lower domain purity, and smaller domain size compared to the PBDTTT‐EFT:PC₇₁BM blend. Incomplete photoluminescence quenching is also found in the ICBA blend with transient absorption measurements showing faster recombination dynamics at short timescales. Transient photovoltage measurements highlight further differences in recombination at longer timeframes due to the more intermixed morphology of the ICBA blend. Interestingly, a mild thermal treatment improves the performance of PBDTTT‐EFT:ICBA cells which is exploited in the fabrication of a homo PBDTTT‐EFT:ICBA tandem solar cell with PCE of 9.0% and V_OC of 1.93 V.     

Structural and electronic properties of diazonium functionalized (4, 4) single walled carbon nanotube: an ab initio study

In this work, ab initio density functional theory (DFT) calculations are performed to study the structural and electronic properties of diazonium reagent functionalized (4, 4) single-walled carbon nanotube (SWCNT). We find the aryl group covalently bonds with SWCNT and prefers to be perpendicular to the side wall of nanotube. It has a rotational barrier of 0.35 eV around the formed aryl-tube bond axis and should be thermodynamically stable at room temperature. Additionally, new peaks appeared around the Fermi energy in the density of state (DOS) due to the weak band dispersion. Increasing of the coverage of the functional group will result in significant upshift of the Fermi level.     

CoS NWs/Au Hybridized Networks as Efficient Counter Electrodes for Flexible Sensitized Solar Cells

A newly designed counter electrode (CE) composed of a hybridized structure of Au networks and cobalt sulfide (CoS) nanowire (NW) arrays is presented for flexible dye‐sensitized solar cells (DSSCs) and quantum dot‐sensitized solar cells (QDSSCs). The sheet resistance of the Au networks electrode is ≈10 Ω sq^?1 with a transmittance up to 90%. The CoS NWs/Au hybridized networks show excellent electrocatalytic activity and lower charge transfer resistance toward the reduction of both S_x^2? ions and I₃^? ions. The hybridized electrode exhibits remarkable mechanical strength and no obvious changes in morphology and sheet resistance even after 500 bending cycles; 3.13% and 4.73% efficiency are obtained by utilizing CoS/Au hybridized networks as CEs in TiO₂ nanotube array (TNAR) based DSSCs and QDSSCs. This work provides a novel approach to fabricate flexible, transparent, conductive, and catalytically active electrodes for QDSSCs and DSSCs and pomotes the development of transparent percolation conductive films for photovoltaics.     

Interfacing Pristine C60 onto TiO2 for Viable Flexibility in Perovskite Solar Cells by a Low‐Temperature All‐Solution Process

A low‐temperature solution‐processed strategy is critical for cost‐effective manufacture of flexible perovskite solar cells (PSCs). Based on an aqueous‐processed TiO₂ layer, and conventional fullerene derivatives replaced by a pristine fullerene interlayer of C₆₀, herein a facile interface engineering for making all‐solution‐processed TiO₂/C₆₀ layers in flexible n‐i‐p PSCs is reported. Due to the improvement of the perovskite grain quality, promotion of interfacial charge transfer and suppression of interfacial charge recombination, the stabilized power conversion efficiency for the flexible PSCs reaches as high as 16% with high bending resistance retention (≈80% after 1500 cycles) and high light‐soaking retention (≈100% after 100 min). In addition, the stabilized efficiency is over 19% for the rigid TiO₂/C₆₀‐based PSCs. The present work with the facile low‐temperature solution process renders the practicability for high‐performance flexible PSCs applied to wearable devices, portable equipment, and electric vehicles.     

The Effect of PCBM Dimerization on the Performance of Bulk Heterojunction Solar Cells

Increasing the lifetime of polymer based organic solar cells is still a major challenge. Here, the photostability of bulk heterojunction solar cells based on the polymer poly[4,4′‐bis(2‐ethylhexyl)dithieno[3,2‐b:2′,3′‐d]silole)‐2,6‐diyl‐alt‐[2,5‐bis(3‐tetradecylthiophen‐2‐yl)thiazole[5,4‐d]thiazole)‐1,8‐diyl] (PDTSTzTz) and the fullerene [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PC₆₀BM) under inert atmosphere is investigated. Correlation of electrical measurements on complete devices and UV‐vis absorption measurements as well as high‐performance liquid chromatography (HPLC) analysis on the active materials reveals that photodimerization of PC₆₀BM is responsible for the observed degradation. Simulation of the electrical device parameters shows that this dimerization results in a significant reduction of the charge carrier mobility. Both the dimerization and the associated device performance loss turn out to be reversible upon annealing. BisPC₆₀BM, the bis‐substituted analog of PC₆₀BM, is shown to be resistant towards light exposure, which in turn enables the manufacture of photostable PDTSTzTz:bisPC₆₀BM solar cells.     

Inverted Tandem Polymer Solar Cells with Polyethylenimine‐Modified MoOX/Al2O3:ZnO Nanolaminate as the Charge Recombination Layers

A new charge recombination layer for inverted tandem polymer solar cells is reported. A bilayer of MoO_X/Al₂O₃:ZnO nanolaminate is shown to enable efficient charge recombination in inverted tandem cells. A polymer surface modification on the MoO_X/Al₂O₃:ZnO nanolaminate bilayer increases the work function contrast between the two outward surfaces of the charge recombination layer, further improving the performance of tandem solar cells. An analysis of the electrical, optical, and surface properties of the charge recombination layer is presented. Inverted tandem polymer solar cells, with two photoactive layers comprising poly (3‐hexylthiophene) (P3HT):indene‐C₆₀ bisadduct (IC₆₀BA) for the bottom cell and poly[(4,8‐bis‐(2‐ethylhexyloxy)‐benzo[1,2‐b:4,5‐b']dithiophene)‐2,6‐diyl‐alt‐(4‐(2‐ethylhexanoyl)‐thieno[3,4‐b]thiophene))‐2,6‐diyl] (PBDTTT‐C):[6,6]‐phenyl C₆₁ butyric acid methyl ester (PC₆₀BM) for the top cell, yield an open‐circuit voltage of 1481 mV ± 15 mV, a short‐circuit current density of 7.1 mA cm^?2 ± 0.1 mA cm^?2, and a fill factor of 0.62 ± 0.01, resulting in a power conversion efficiency of 6.5% ± 0.1% under simulated AM 1.5G, 100 mW cm^?2 illumination.     

Nongeminate Recombination in Planar and Bulk Heterojunction Organic Solar Cells

Nongeminate recombination in organic solar cells based on copper phthalocyanine (CuPc) and C₆₀ is investigated. Two device architectures, the planar heterojunction (PHJ) and the bulk heterojunction (BHJ), are directly compared in view of differences in charge carrier decay dynamics. A combination of transient photovoltage (TPV) experiments, yielding the small perturbation charge carrier lifetime, and charge extraction measurements, providing the charge carrier density is applied. In organic solar cells, charge photogeneration and recombination primarily occur at the donor–acceptor heterointerface. Whereas the BHJ can often be approximated by an effective medium due to rather small scale phase separation, the PHJ has a well defined two‐dimensional heterointerface. In order to study nongeminate recombination dynamics in PHJ devices the charge accumulation at this interface is most relavent. As only the spatially averaged carrier concentration can be determined from extraction techniques, the charge carrier density at the interface n_int is derived from the open circuit voltage. Comparing the experimental results with macroscopic device simulation, the differences of recombination and charge carrier densities in CuPc:C₆₀ PHJ and BHJ devices are discussed with respect to the device performance. The open circuit voltage of BHJ is larger than for PHJ at low light intensities, but at 0.3 sun the situation is reversed: here, the PHJ can finally take advantage of its generally longer charge carrier lifetimes, as the active recombination region is smaller.     

Tissue Sites of Uptake ofC-Labeled C60

This paper describes thein vivobehavior and potential metabolism of C₆₀and a more water-soluble quaternary ammonium salt-derivatized C₆₀. In both cases, a¹⁴C-labeled fullerene core was utilized for the target molecules that were intravenously injected into female Sprague–Dawley rats. The¹⁴C-labeled C₆₀(*C₆₀) was rapidly (within 1 min) cleared from the circulation and the majority of the *C₆₀accumulated in the liver (90–95%). *C₆₀was not eliminated from the liver over the 120-h period of this study. Our results also suggest that C₆₀is not metabolized by the typical oxidative patterns characteristic of other polycyclic aromatics. Therefore, although not acutely toxic, use of C₆₀, or its derivatives that could be cleaved back to the parent C₆₀in vivo, would likely lead to long-term fullerene accumulation in the liver. The uptake of *C₆₀and¹⁴C-labeled ammonium salt-derivatized C₆₀(1)by human keratinocytesin vitroshowed that while both *C₆₀and1are readily taken up by cells,1accumulates more slowly. Additionally, while C₆₀, at rather high concentrations (2.0 μM) and over extended periods of time (8 days), is able to inhibit the growth of human keratinocytes by about 50%, this effect showed little, if any, photoinducability.     

Relating Frontier Orbital Energies from Voltammetry and Photoelectron Spectroscopy to the Open‐Circuit Voltage of Organic Solar Cells

For 19 diketopyrrolopyrrole polymers, the highest occupied molecular orbital (HOMO) energies are determined from i) the oxidation potential with square‐wave voltammetry (SWV), ii) the ionization potential using ultraviolet photoelectron spectroscopy (UPS), and iii) density functional theory (DFT) calculations. The SWV HOMO energies show an excellent linear correlation with the open‐circuit voltage (V_oc) of optimized solar cells in which the polymers form blends with a fullerene acceptor ([6,6]‐phenyl‐C₆₁‐butyl acid methyl ester or [6,6]‐phenyl‐C₇₁‐butyl acid methyl ester). Remarkably, the slope of the best linear fit is 0.75 ± 0.04, i.e., significantly less than unity. A weaker correlation with V_oc is found for the HOMO energies obtained from UPS and DFT. Within the experimental error, the SWV and UPS data are correlated with a slope close to unity. The results show that electrochemically determined oxidation potentials provide an excellent method for predicting the V_oc of bulk heterojunction solar cells, with absolute deviations less than 0.1 V.     

Decoupling Photocurrent Loss Mechanisms in Photovoltaic Cells Using Complementary Measurements of Exciton Diffusion

Significant work has been directed at measuring the exciton diffusion length (L_D) in organic semiconductors due to its significance in determining the performance of photovoltaic cells. Several techniques have been developed to measure L_D, often probing photoluminescence or charge carrier generation. Interestingly, in this study it is shown that when different techniques are compared, both the diffusive behavior of the exciton and active carrier recombination loss pathways can be decoupled. Here, a planar heterojunction device based on the donor–acceptor pairing of boron subphthalocyanine chloride‐C₆₀ is examined using photoluminescence quenching, photovoltage‐, and photocurrent‐based L_D measurement techniques. Photovoltage yields the device relevant L_D of both active materials as a function of forward bias subject to geminate recombination losses. These values are used to accurately predict the photocurrent as a function of voltage, suggesting geminate recombination is the dominant mechanism responsible for photocurrent loss. By combining these measurements with photocurrent and photoluminescence quenching, the intrinsic L_D, as well as the voltage‐dependent charge transfer state dissociation and charge collection efficiencies are quantitatively determined. The results of this work provide a method to decouple all relevant loss pathways during photoconversion, and establish the factors that can limit the performance of excitonic photovoltaic cells.     

Identification of the alga known as <Emphasis Type="Italic">Nannochloropsis</Emphasis> Z-1 isolated from a prawn farm in Hainan,China as <Emphasis Type="Italic">Chlorella</Emphasis>

An alga known as “Nannochloropsis”, isolated from a prawn farm in Hainan, China, has been critically investigated and identified as Chlorella, a member of the Chlorophyceae based on fatty acid composition, ultrastructure, and 18S rDNA. Cells of this alga were spherical, measured by 1–6 μm in diameter and were enclosed in thin walls of approximately 0.04 μm thickness. They contained several small mitochondria, two to three thylakoids and had no vacuoles. There were many pyrenoids in the algal cells and their thylakoid lamellae were sparse and not translucent. Many lipid droplets were present in the cytoplasm. The total lipid content of this alga was 3% per gram dry weight and its major fatty acids were C_16:0, C_18:0, C_18:1, C_18:2, C_18:3 and C_20:0. Eicosapentaenoic acid (C_20:5, EPA) was not detected. The length of its 18S rDNA sequence was 1,712 bp. 18S rDNA sequence analyses indicated that this alga was a species of Chlorella.     

Carrier Transport and Recombination in Efficient “All‐Small‐Molecule” Solar Cells with the Nonfullerene Acceptor IDTBR

Reaching device efficiencies that can rival those of polymer‐fullerene Bulk Heterojunction (BHJ) solar cells (>10%) remains challenging with the “All‐Small‐Molecule” (All‐SM) approach, in part because of (i) the morphological limitations that prevail in the absence of polymer and (ii) the difficulty to raise and balance out carrier mobilities across the active layer. In this report, the authors show that blends of the SM donor DR3TBDTT (DR3) and the nonfullerene SM acceptor O‐IDTBR are conducive to “All‐SM” BHJ solar cells with high open‐circuit voltages (V_OC) >1.1 V and PCEs as high as 6.4% (avg. 6.1%) when the active layers are subjected to a post‐processing solvent vapor‐annealing (SVA) step with dimethyl disulfide (DMDS). Combining electron energy loss spectroscopy (EELS) analyses and systematic carrier recombination examinations, the authors show that SVA treatments with DMDS play a determining role in improving charge transport and reducing non‐geminate recombination for the DR3:O‐IDTBR system. Correlating the experimental results and device simulations, it is found that substantially higher BHJ solar cell efficiencies of >12% can be achieved if the IQE and carrier mobilities of the active layer are increased to >85% and >10^?4 cm² V^?1 s^?1, respectively, while suppressing the recombination rate constant k to <10^?12 cm³ s^?1.     

Interface Design to Improve the Performance and Stability of Solution‐Processed Small‐Molecule Conventional Solar Cells

A systematic study on the effect of various cathode buffer layers on the performance and stability of solution‐processed small‐molecule organic solar cells (SMOSCs) based on tris{4‐[5‐(1,1‐dicyanobut‐1‐en‐2‐yl)‐2,2‐bithiophen‐5‐yl]phenyl}amine (N(Ph‐2T‐DCN‐Et)₃):6,6‐phenyl‐C71‐butyric acid methyl ester (N(Ph‐2T‐DCN‐Et)₃:PC₇₀BM) is presented. The power conversion efficiency (PCE) in these systems can be significantly improved from approximately 4% to 5.16% by inserting a metal oxide (ZnO) layer between the active layer and the Al cathode instead of an air‐sensitive Ba or Ca layer. However, the low work‐function Al cathode is susceptible to chemical oxidation in the atmosphere. Here, an amine group functionalized fullerene complex (DMAPA‐C₆₀) is inserted as a cathode buffer layer to successfully modify the interface towards ZnO/Ag and active layer/Ag functionality. For devices with ZnO/DMAPA‐C₆₀/Ag and DMAPA‐C₆₀/Ag cathodes the PCEs are improved from 2.75% to 4.31% and to 5.40%, respectively, compared to a ZnO/Ag device. Recombination mechanisms and stability aspects of devices with various cathodes are also investigated. The significant improvement in device performance and stability and the simplicity of fabrication by solution processing suggest this DMAPA‐C₆₀‐based interface as a promising and practical pathway for developing efficient, stable, and roll‐to‐roll processable SMOSCs.