Enhanced electronic quality of perovskite via a novel C60 o

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Enhanced electronic quality of perovskite via a novel C60 oquinodimethane bisadducts toward efficient and stable perovskite solar cells Huayang Li, Liuxing Guo, Chuan-Nan Li, Chen Wang, Ge Wang, Shanpeng Wen, Jiaxin Wu, Wei Dong, Zong-Jun Li, and Shengping Ruan ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.9b00368 • Publication Date (Web): 08 Apr 2019 Downloaded from http://pubs.acs.org on April 10, 2019

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ACS Sustainable Chemistry & Engineering

Enhanced electronic quality of perovskite via a novel C60 o-quinodimethane bisadducts toward efficient and stable perovskite solar cells Huayang Li, †,┴ Liuxing Guo, †,┴ Chuan-Nan Li, † Chen Wang, † Ge Wang, † Shanpeng Wen, *,† Jiaxin Wu, † Wei Dong,† Zong-Jun Li, *,‡ Shengping Ruan†

†State

Key Laboratory on Integrated Optoelectronics and college of Electronic Science &

Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012, P. R. China

‡State

Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied

Chemistry, Chinese Academy of Sciences, 5625 Renmin Street, Changchun, Jilin 130022, P. R. China

Email: [email protected]

Email: [email protected]

ACS Paragon Plus Environment 1

ACS Sustainable Chemistry & Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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Abstract: As one of the potential photovoltaic technologies, the planar perovskite solar cells (PSCs) are arousing worldwide interest for their many advantages. Now, PSCs are developing toward the direction of high-performance and longevity. However, the defects of polycrystalline perovskite active layer limit the further improvement of device performance. Seeking simple and efficient strategies to reduce these trap states in perovskite active layer is highly desired. Here, a novel non-functionalized fullerene C60 o-quinodimethane bisadducts [C60(QM)2] was dissolved in the chlorobenzene (CB) solvent and introduced into CH3NH3PbI3 active layer by antisolvent dripping. Results showed that the introduced C60(QM)2 could effectively reduce the trap density of MAPbI3 active layer, facilitating carriers extraction/injection from CH3NH3PbI3 to spiroOMeTAD. As a result, the champion PCE of 18.4% for the PSCs based on CH3NH3PbI3/C60(QM)2 was obtained, which increased by 10.1% compared with the 16.7% for reference device. Meanwhile, the air stability for C60(QM)2-passivated PSCs was also improved significantly. This approach provides one of the directions for designing high efficient and air stable PSCs.

Key words: trap density, high-performance, air stable, perovskite solar cell


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INTRODUCTION Organic-metal-halides based perovskite solar cells (PSCs) are arousing numerous attentions in recent years since the great progress in device efficiency, increasing rapidly from the 3.8% in 20091 to the 23.3% in 2018.2 This makes the PSCs become one of promising photovoltaic technologies. In General, for highly efficient PSCs, the perovskite films were usually sandwiched by interfacial transport layers, followed by a metal counter electrode.3-5 The rapid progresses that have been made for the PSCs could mainly originate from the excellent photoelectric characteristic of these perovskites. For example, the high hole/electron mobility, the large extinction coefficient and long charge carrier diffusion lengths.6-8 Despite these significant progresses, the solution-processed polycrystalline perovskite films inevitably have numerous trap states existing in the grain boundaries (GBs) and surface, including the under-coordinated halide anions or the mental cations induced by the evaporation of methylammonium iodide, as well as the ions migration.9-14 These trap states will capture the electron/hole, leading to the unwanted carrier recombination. This will cause serious energy loss, which limits the performance of the devices.15 Meanwhile, it has been observed that the degradation of the perovskite polycrystalline films usually begins at these trap sites and the defects will facilitate the polycrystalline perovskite active layer’s decomposition when exposed



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to the oxygen, moisture, and light enviromment.16 Therefore, seeking some strategies to heal these trap states at GBs or the surface to fabricate efficient and long-lived PSCs is necessary. Considering the ionic nature of perovskite crystals, the under-coordinated defects in these materials are typically charged, negatively or positively. Therefore, different passivation molecules equipped with Lewis acid or Lewis base functional groups have been proposed to neutralize these charged defects so that these trap states can be effectively reduced.17-20 The Lewis base groups include carbonyl (-C=O) or cyanide (-C≡N) etc. that can donate its lone pair of electrons and neutralize charges at metal cations. Building blocks of organic molecules such as thiophene or pyridine have also been proved to be effective in forming Lewis adducts with positively charged Pb2+ ions.21-23 While for the Lewis acid, quaternary ammonium (R4N+) or ammonium-group (-NH3+) containing molecules, as well as some strong halogen bond donors (Lewis acid, electron acceptor) can effectively mitigate the coordinatively unsaturated halide anions defects (X-) and improve charge transport/collection efficiency.17, 24, 25 In addition, these Lewis groups were designed to anchor hydrophobic organic molecules to improve the storage stability of device at the same time. Among large selections, many groups chose fullerene cage as framework and developed a type of functionalized passivators such as bis-PCBM, fluoroalkylsubstituted fullerene (DF-C60) and so on.26-28 They were introduced into the perovskite film by doping (BHJ) or anti-solvent process (PHJ) to realize perovskite film with better electronic quality. However, functionalization imposes complicated synthetic procedure that is not easy to obtain. In fact, as an extraordinary electron transporting material, fullerene’s intrinsic electron-


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accepting property also plays critical role in passivating halide-rich defects by electron transfer, which has not been intensively studied in previous work.29 Therefore, more efforts are required to develop successful non-functionalized fullerene passivators and confirm such interaction. In this work, we introduced one novel non-functionalized fullerene acceptors (C60(QM)2) into the perovskite film by the anti-solvent deposition method. The results show that C60(QM)2 could potentially passivate these defects existing in polycrystalline MAPbI3 layer and improve carriers extraction at perovskite/HTM interface, resulting in the increase of the short-circuit current density (Jsc), open-circuit voltage (Voc) and fill factor (FF). Consequently, the modified device with C60(QM)2 yields a higher efficiency with 18.4% in comparison with that (16.7%) of the reference PSCs, and the hysteresis of the C60(QM)2-modified device is also suppressed. In addition, introduced C60(QM)2 could also protect MAPbI3 film from the moisture ingress for its hydrophobic property. Therefore, the stability of the device cooperated with C60(QM)2 is also improved significantly in the ambient atmosphere, which still maintains over 80% of its original efficiency after 35 days. EXPERIMENTAL SECTION Preparing SnO2 and TiO2 precursors. We prepared the TiO2 precursor according to the literature.30 Firstly, tetrabutyl titanate (10 mL) were added into absolute ethyl alcohol (90 mL) and the solution was stirred at 25 oC for 0.5 h. Secondly, equal volume (10 mL) of acetylacetone and acetic acid were mixed together and then poured into the above solutions, followed by stirring for another 0.5 h. Finally, adding distilled water with 10 mL into the mixed precursors.



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After being stirred at 25 oC for 10 h, the TiO2 precursor was placed in the drying cupboard for one day without vibration. The synthesis of SnO2 precursor is similar with the reference.31 The 0.05 M SnO2 precursor was obtained by dissolving 0.115 g SnCl2·2H2O in anhydrous ethanol (10 mL) with stirring for 120 min. Devices Fabrication. FTO substrates were cleaned ultrasonically in detergent, acetone and isopropyl alcohol for each fifteen minutes. Then these FTO-based glasses were annealed at 500 oC

for 1h in the muffle to remove the residual organics. Before being used, the FTO was treated

by the ultraviolet-O3 for 10 min. Then TiO2 precursor was spun onto these FTO bases for 30 s at 3000 rpm, followed by sintering at 130 oC for ten minutes and 450 oC for 120 min. When the TiO2 films cooled down, SnCl2 precursors were spun onto these TiO2 films with the same speed and time as TiO2. Then these films were sintered for 60 min at 180 oC. Prior to depositing perovskite films, the as-prepared films were treated with the ultraviolet-O3 for another 10 min. The perovskite layers can be obtained by antisolvent dripping.32 Perovskite precursor was prepared by dissolving CH3NH3I and PbI2 (molar ration, 1:1) in the dimethylsulfoxide (DMSO)/N, N-dimethylformamide (DMF) mixed solvent with the volume ratio of 1:4. The concentration of the CH3NH3PbI3 precursor was 1.2 M. After being stirred for 8 h at 25 oC, CH3NH3PbI3 precursors were spin-coated on these TiO2/SnO2 films, then 100 μL CB with and without C60(QM)2 was quickly dripped onto the perovskite films to stop the films from becoming turbid. After being annealed at 70 oC for 2 min and 120 oC for 10 min, these perovskite layers were obtained. The Spiro-OMeTAD solution was prepared by dissolving 72.3 mg Spiro-


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OMeTAD ，17.5 μL lithium salt acetonitrile solution with the concentration of 520 mg/mL and 28.8 μL TBP in 1 mL CB. Then the hole transport layer was obtained by spin-coating 25 μL Spiro-OMeTAD solution on CH3NH3PbI3 layer at 4000 rpm for 30 s. Finally, Ag electrode with thickness of 90 nm was evaporated thermally on the Spiro-OMeTAD layer. The measured area for PSCs was fixed at 0.06 cm2. Characterization. The Scanning Electron Microscope (SEM) with the model of FEI MAGELLAN 400 was applied to measure the surface and cross-section images of perovskite films and devices. The Rigaku X-ray diffractometer was carried out to investigate the crystallization of as-prepared films. The solar simulator with the type of Oriel 300 W was used to provide 100 mW/cm2 simulated sunlight. Keithley 2601 was used to measure the J-V curves of fabricated PSCs. Crowntech QTest Station 1000 AD was adopted to measure the external quantum efficiency (EQE) of the prepared PSCs. The UV-vis spectrum of MAPbI3 layers was characterized with Shimadzu UV-1700. RESULTS AND DISCUSSION It can be observed from Figure 1a that the final PSCs presents the configuration with FTO/TiO2/SnO2/MAPbI3:C60(QM)2/Spiro-OMeTAD/Ag. The detailed fabrication process is demonstrated in device fabrication and the molecular structure for the C60(QM)2 is exhibited in the Figure 1b, which is widely served as electron acceptor material in organic photovoltaic field due to its relative good electronic properties.33 Figure 1c presents the corresponding crosssection SEM image for the final PSCs, it is noted that compared with the MAPbI3 layer thickness,



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the grain sizes of many perovskite crystallites are larger and most of the GBs are vertical to TiO2/SnO2 layer, which could effectually minimizes these GB energy and improve the carrier transport. Finally, the Figure 1d presents schematic diagram of the spin-coating strategy to introduce the C60(QM)2 into the perovskite film.

Figure 1. (a) The configuration for the final devices, (b) the molecular configuration for C60(QM)2, (c) SEM image of the cross-section of PSCs treated with C60(QM)2, (d) the diagrammatic sketch for the spin-coating process of fabricating MAPbI3 active layer. It has been reported that the concentrations of polymer in chlorobenzene antisolvent have obvious influence on the PSCs performance.22 Thus, the optimization of the C60(QM)2 concentration (mg mL-1) in CB solvent is firstly investigated. Figure S1 exhibits the J-V curves for these devices prepared by various C60(QM)2 concentration in chlorobenzene, and Table S1 gives the detailed performance parameters of corresponding PSCs. It is observed that on


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increasing the C60(QM)2 concentrations, the device efficiencies firstly increase, followed by decrease subsequently and the optimal concentration for C60(QM)2 is 0.4 mg mL-1. Figure 2a presents the current-voltage characteristics of the champion PSCs based MAPbI3 and MAPbI3:C60(QM)2 under different scan direction. The Table 1 provides the corresponding device parameters, it can be seen that the control PSCs show the reverse scan PCE of 16.7% and forward scan PCE of 13.5%. In contrast, the efficiency for the C60(QM)2-modified PSCs significantly increases to 18.4% (reverse scan) and the 17.5% (forward scan), which shows a significantly reduced hysteresis. The Figure 2b shows the EQE of the PSCs based on MAPbI3 and MAPbI3:C60(QM)2. It can be seen that the calculated Jsc from the corresponding EQE are 20.7 and 21.2 mA cm-2 respectively, consistent with the results obtained from J-V measurement. Figure 3c shows the steady-state PCE and current density for MAPbI3:C60(QM)2 based device measured at 0.9 V for 150 s. As can be seen, the current density quickly increases to 19.92 mA cm-2 and stabilized, the corresponding steady-state device efficiency reaches to 17.93%. In order to further confirm the repeatability of the PCE, 22 PSCs with or without the C60(QM)2 treatment were fabricated, respectively. The Figure 2d shows the PCE distribution of the devices, and it indicates that the devices with C60(QM)2 treatment have higher PCE, revealing the potential positive effect of C60(QM)2 in PSCs.



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Figure 2. (a) The J-V characteristics for the PSCs based MAPbI3 and MAPbI3:C60(QM)2, (b) EQE of the corresponding devices, (c) steady-state output power of the best device with C60(QM)2 measured at 0.9 V for 150 s. (d) The distribution of device efficiency. Table 1. The device performance parameters based on MAPbI3 and MAPbI3:C60(QM)2. device

control

C60(QM)2

Scan

Jsc/mA

direction

cm-2

Voc/V

FF

η(%)

Hysteresis index34

Forward

21.7

1.04

0.6

13.5

Reverse

21.9

1.06

0.72

16.7

Forward

22.3

1.09

0.72

17.5

Reverse

22.4

1.08

0.76

18.4

0.189

0.046


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To find out the role of the introduced C60(QM)2 in enhancing PSCs efficiency, the morphology and crystallinity of the MAPbI3 film with and without C60(QM)2 are firstly investigated. The Figure 3a, b exhibits the surface SEM images of MAPbI3 and MAPbI3:C60(QM)2 films on FTO/TiO2/SnO2 substrates. As shown in Figure 3a, b, the control MAPbI3 film has clear GBs and smooth morphology. However, by incorporating the C60(QM)2 into the MAPbI3 film, we find that some C60(QM)2 distribute on perovskite layer surface uniformly and some GBs of the MAPbI3 film become blurred, which is beneficial for reducing the structure defects located at GBs and surface of the MAPbI3 film. These results are in line with the literature report.22 In addition, by the nano measurer analysis, the calculated average grain sizes of the MAPbI3 with and without C60(QM)2 are 460 and 453 nm, respectively, which don’t show obvious change due to the low concentration of the C60(QM)2. The surface morphology of the MAPbI3 with and without C60(QM)2 is also measured by atomic force microscope (AFM). It can be seen from Figure S2 that the root-mean-square surface roughness (Rq) decreases from 10.6 nm for MAPbI3 to 7.18 nm after introducing C60(QM)2. It indicates that the introduced C60(QM)2 can afford improved interfacial contact between MAPbI3 and Spiro-OMeTAD, which benefits for the hole extraction enhancement. Figure 3c exhibits XRD pattern of MAPbI3 and MAPbI3:C60(QM)2 films. It presents that both MAPbI3 layers show cubic phase crystal structure35. Meanwhile, the main diffraction peaks for (110) and (220) crystal faces, which are located at 14.2o and 28.6o, are both observed, indicating the high crystallization for the both perovskite films. Figure 3d exhibits the UV-Vis spectrum for both perovskite layers, it is observed that the absorption for MAPbI3



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and MAPbI3:C60(QM)2 films is similar, which further supports the above results. Therefore, it confirms that the introduced C60(QM)2 has almost no effect on the crystallinity of the MAPbI3 film, suggesting that the enhanced device efficiency may be in connection with the passivated defects and improved interface contact instead of the crystallization or visible absorption ability of the MAPbI3 film.

Figure 3. (a) The top-view SEM images for the pristine perovskite film and (b) MAPbI3:C60(QM)2 film, (c) XRD pattern of MAPbI3 and MAPbI3:C60(QM)2 layers, (d) UV-vis spectrum of MAPbI3 and MAPbI3:C60(QM)2 layers.


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To confirm that the reduced trap states lead to the enhanced device performance, we carried out the photoluminescence (PL) and time-resolved photoluminescence (TRPL) measurement. Figure 4a exhibits the PL spectrum for the bare MAPbI3 and MAPbI3:C60(QM)2 films. It is noted that the C60(QM)2 coated perovskite film has stronger PL intensity compared with the bare MAPbI3 film. In addition, the PL peak shows slight blueshift with the introduction of the C60(QM)2, which indicates that the introduced C60(QM)2 could eliminate some defects at the surface or GBs .15,

18

Then the PL spectrum for the glass/MAPbI3/spiro-OMeTAD were

measured. From Figure S3, we can see that the PL quenching for MAPbI3:C60(QM)2/spiroOMeTAD film is more complete in comparison with the pristine film, suggesting enhanced carrier extraction at the MAPbI3:C60(QM)2/spiro-OMeTAD interface. This can be interpreted as the improved interfacial contact between MAPbI3 and Spiro-OMeTAD and the reduced trap states at the surface of the MAPbI3 passivated by the C60(QM)2, ensuring that more holes could be rapidly extracted by spiro-OMeTAD layer. To further investigate reasons behind the enhanced carrier extraction at MAPbI3:C60(QM)2/spiro-OMeTAD interface, the UPS measurement for the MAPbI3 and MAPbI3:C60(QM)2 are carried out. It can be seen from the Figure S4 that the valence band maxima (VBM) of the MAPbI3 and MAPbI3:C60(QM)2 are -5.32 eV and -5.59 eV, respectively. The deeper VBM for MAPbI3:C60(QM)2 increase the energy difference with the HOMO of Spiro-OMeTAD, which provides stronger driving force for carriers extraction/injection at the perovskite/HTL interface. Therefore, the passivated trap states induced

by

C60(QM)2,

improved

interfacial

contact

and

band

alignment

of



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MAPbI3:C60(QM)2/spiro-OMeTAD lead to the enhanced hole extraction. Finally, the lifetime of these charge carriers for MAPbI3 and MAPbI3:C60(QM)2 films was calculated by fitting the TRPL spectra (Figure 4b) with the following decay equation: Y=γ0+A1 (-t/τ1)+A2 exp(-t/τ2) (1) Where A1 and A2 represent decay amplitude, τ1 is the lifetime of the fast recombination, while τ2 is the slow recombination lifetime which is associated to the trap-assisted recombination and the γ0 is a constant representing the baseline offset.18 As shown in Figure 4b, the τ1 and τ2 of C60(QM)2-contained perovskite film are 5.42 and 140.3 ns, respectively. By contrast, the bare perovskite film shows lower τ2 of 71.9 ns and the τ1 (4.59 ns) doesn’t show obviously change. The larger τ2 for MAPbI3:C60(QM)2 film suggests the reduced trap-assisted recombination, indicating that the C60(QM)2 treatment can reduce these defects existing in the MAPbI3 film and suppress carrier recombination effectively. Therefore, these above results are likely to be the reason for the enhanced FF and Voc of the devices, which agrees well with our expectation.


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Figure 4. (a) PL and (b) TRPL spectrum for the MAPbI3 layers with and without C60(QM)2 deposited on glass. In order to understand the influence of the introduced C60(QM)2 on charge carrier transport in the device, we performed the electrical impedance spectroscopy (EIS) measurement in dark condition by adjusting the range of frequency between 20 Hz and 20 MHz. The Figure 5 shows the Nyquist plots for the PSCs based MAPbI3 and MAPbI3:C60(QM)2. As can be seen, the Nyquist plots contain two diacritical characteristic arcs, corresponding to the contact resistance (Rco) at high frequency region and the recombination resistance (Rrec) at low frequency region.19, 36

The Rco and Rrec can be extrapolated by the equivalent circuit model given as inset in the

Figure 5. It shows that the PSCs based MAPbI3:C60(QM)2 has larger Rrec compared with the pristine PSCs. This indicates that the induced C60(QM)2 could effectually eliminate surface defects of MAPbI3 active layer and reduce charge carrier’s recombination at MAPbI3/spiroOMeTAD interface. In addition, the device with C60(QM)2 shows smaller Rco (68.85 Ω) compared with that (86.7 Ω) of the control device, further confirming the improved contact at the



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perovskite/Spiro-OMeTAD interface. These results are expected to yield the lower series resistance (Rs) and higher FF, Voc for the C60(QM)2-contained device.

Figure 5. The EIS of PSCs based MAPbI3 and MAPbI3:C60(QM)2 measured in the dark. In addition, to evaluate the defect density of the device based MAPbI3 and MAPbI3:C60(QM)2, we fabricated the electron-only devices, which possess the structure of FTO/TiO2/SnO2/MAPbI3 (w/wo C60(QM)2 treatment)/PC61BM/Ag. Figure 6 presents the I-V curves of corresponding electron-only devices based MAPbI3 and MAPbI3:C60(QM)2 under dark condition. It can be seen that three regions could be observed clearly from the log-log coordinate of I-V curves, consisting of the ohmic regime in low bias, the trap-filled regime, and the space charge limited current (SCLC) region. It is noted that the density of defect (nt) is determined by the trap-filling limited onset voltage (VTFL) with following formula: VTFL =entL2/2εε0 (2)


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In which ε0 and ε represent vacuum permittivity and MAPbI3 film dielectric constant, respectively, e represents elementary charge and L represents perovskite active layer thickness.3739

It can be seen that the VTFL for the devices with and without C60(QM)2 treatment is 0.33 and

0.37 V, respectively. The derived trap density of the corresponding devices is 6.5×1015 cm-3 and 7.3×1015 cm-3, respectively. This result reveals that the introduced C60(QM)2 can lower the trap states of perovskite film, leading to reduced nonradiative recombination. This is benefit for extending charger carrier lifetime. In addition, the carrier mobility can be obtained in the SCLC region by the Mott-Gurney equation: J=9εε0μV2/8L3 (3) The V and μ represent the bias voltage and charge mobility, respectively. The electron mobility (μe) for the device with C60(QM)2 treatment was extrapolated to be 0.66 cm2 V-1 s-1, while the μe decreases to 0.4 cm2 V-1 s-1 for the pristine device. The increased electron mobility can be ascribed to that the induced C60(QM)2 can passivate the trap sites existing in MAPbI3 layer, which facilitates the electron transport. Meanwhile, we also fabricated the device possessing a configuration of FTO/PEDOT:PSS/MAPbI3(w/wo C60(QM)2)/Au to measure the device hole mobility. As shown in Figure S5, the derived μh increases from 0.57 cm2 V-1s-1 for MAPbI3 based device to 0.82 cm2 V-1s-1 for the MAPbI3:C60(QM)2 based device. Furthermore, we calculate the ration of electron mobility and hole mobility (μe/μh). The value of μe/μh decreases from 1.43 for MAPbI3 based device to 1.24 after C60(QM)2 treatment, indicating the charge



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transport in the device become more balanced. As a result, the enhanced and more balanced charge transport contributes to the enhanced efficiency.

Figure 6. The dark I-V measurement for the electron-only device based on MAPbI3 and MAPbI3:C60(QM)2. Finally, the stability for corresponding PSCs stored in ambient atmosphere with the humidity of 20% without encapsulation was investigated. The Figure 7a exhibits the recorded stability of the devices with and without C60(QM)2. As can be seen, introduced C60(QM)2 can improve the air stability of the device significantly. For example, the PCE for control PSCs degrades to 49% after 11 days, while the C60(QM)2-passivated device can still maintain the 80% of the initial PCE after 35 days. It has been demonstrated that instability of MAPbI3 active layer has seriously negative effect on the PSCs stability. The instability of the perovskite film origins from the intrinsic defects and these defects could speed up the decomposition of perovskite active layer once exposed to the moisture. Then the contact angles (CA) of water dripped on MAPbI3 films


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were investigated. It can be seen from Figure 7b, the CA of the water/control perovskite film is 54o, while the CA for the perovskite film treated with C60(QM)2 increases to 71o, suggesting that the hydrophobicity of the C60(QM)2 can improve the water-resistance of the device, which benefits for obtaining high stable PSCs. Therefore, it is assumed that enhanced stability for the C60(QM)2 containing devices might be associated with the favorable hydrophobic of the perovskite surface and the reduced defects in MAPbI3 active layer.

Figure 7. (a) Recorded stability of the corresponding devices in air with 20% humility at 25oC, (b) contact angles of water dripped on MAPbI3 and MAPbI3:C60(QM)2 layers.



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CONCLUSIONS In conclusion, we have demonstrated a facile strategy to fabricate highly efficient and air stable PSCs by using C60(QM)2 as passivator. The introduced C60(QM)2 can passivate the trap states existing in MAPbI3 active layer, facilitating carrier extraction/injection from MAPbI3 to spiro-OMeTAD effectively. As a result, the champion PCE of 18.4% for C60(QM)2-passivated device with less hysteresis is obtained whereas the efficiency of pristine PSCs is 16.7%. In addition, introduced C60(QM)2 can significantly improve the hydrophobic property of MAPbI3 active layer, resisting the moisture penetrating into MAPbI3 active layer. Consequently, C60(QM)2-contained devices still maintain the over 80% of the original efficiency when the device has been exposed in ambient atmosphere with humidity of 20% for 35 days, which shows an enhanced long-term stability.


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ASSOCIATED CONTENT Supporting Information The J-V characteristics of the PSCs prepared by various concentrations of C60(QM)2 in chlorobenzene. The corresponding device parameters. The AFM images of the MAPbI3 and MAPbI3:C60(QM)2. The PL spectrum for MAPbI3 (w/wo C60(QM)2)/Spiro-OMeTAD. The UPS of MAPbI3 and MAPbI3:C60(QM)2 films. The dark I-V curves of hole-only devices with the configuration of FTO/PEDOT:PSS/MAPbI3 (w/wo C60(QM)2)/Au. AUTHOR INFORMATION Corresponding Authors Email: [email protected]: +86-138-4317-8907. Email: [email protected].

ORCID Shanpeng Wen: 0000-0001-5114-6307 Author Contributions ┴

These two authors make contribution to this work equally.



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Notes The authors declare no competing financial interest. ACKNOWLEDGEMENTS This work was supported by the National Natural Science Foundation of China (Grant No. 61874048), the Jilin Provincial Department of education “13th Five-Year” science and technology project (JJKH20180121KJ), the Project of Jilin Provincial Development and Reform Commission (2018C040-2), the Project of Science and Technology Development Plan of Jilin Province (Grant No. 20180414020GH), and Opened Fund of the State Key Laboratory on Applied Optics.


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efficiency

enhancement.

ACS

Energy

Lett.

2018,

3(1),

30-38,

DOI:

10.1021/acsenergylett.7b00925.



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For TOC only

Synopsis: Enhanced device performance and air stability via trap passivation induced by a novel fullerene derivative C60(QM)2.


Enhanced electronic quality of perovskite via a novel C60 o

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