Photoinduced Field-Effect Passivation from Negative Carrier

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Photoinduced Field-Effect Passivation From Negative Carrier Accumulation for High Efficiency Silicon/Organic Heterojunction Solar Cells Zhaolang Liu, zhenhai yang, Sudong Wu, Juye Zhu, Wei Guo, Jiang Sheng, Jichun Ye, and Yi Cui ACS Nano, Just Accepted Manuscript • DOI: 10.1021/acsnano.7b07222 • Publication Date (Web): 07 Dec 2017 Downloaded from http://pubs.acs.org on December 7, 2017

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Photoinduced Field-Effect Passivation From Negative Carrier Accumulation for High Efficiency Silicon/Organic Heterojunction Solar Cells Zhaolang Liu,†,‡ ,⊥ Zhenhai Yang,†,⊥ Sudong Wu,† Juye Zhu,† Wei Guo,† Jiang Sheng,* ,† Jichun Ye,*,† and Yi Cui*,§ †

Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences,

Ningbo 315201, People’s Republic of China, ‡Shanghai University, School of Materials Science and Engineering, Shanghai 200072, People’s Republic of China, and §Department of Material Science and Engineering, Stanford University, Stanford, California 94305, United States. ⊥These authors contributed equally to the work. KEYWORDS. Photoinduced negative carrier accumulation, photoactive field-effect passivation, antireflective coating, synergistic effect, heterojunction solar cells.

ABSTRACT. Carrier recombination and light management of the dopant-free silicon/organic heterojunction

solar

cells

(HSCs)

based

on

poly(3,4-

ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) are the critical factors in developing high-efficiency photovoltaic devices. However, the traditional passivation technologies can hardly provide efficient surface passivation on the front surface of Si. In this

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study, a photoinduced electric field was induced in a bilayer antireflective coating (ARC) of Polydimethylsiloxane (PDMS) and Titanium oxide (TiO2) films, due to formation of an accumulation layer of negative carriers (O2- species ) under UV (sunlight) illumination. This photoinduced field not only suppressed the silicon surface recombination, but also enhanced the built-in potential of HSCs with 84 mV increment. In addition, this photoactive ARC also displayed the outstanding light-trapping capability. The front PEDOT:PSS/Si HSC with the saturated O2-

received a champion PCE of 15.51% under AM1.5 simulated sunlight

illumination. It was clearly demonstrated that the photoinduced electric field was a simple, efficient and low-cost method for the surface passivation and contributed to achieve a high efficiency when applied in the Si/PEDOT:PSS HSCs.

In recent years, the dopant-free silicon heterojunction solar cells (HSCs) based on the conjugated polymer of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) have been the emerging photovoltaic field with the power conversion efficiency (PCE) boosted to the values over 16%.1-4 In this design, PEDOT:PSS film replaces the boron-diffused front emitter, representing a simple and low-cost way to form p+n heterojunction when contacted on ntype silicon substrate. To further improve the performance of Si/PEDOT:PSS HSCs, a number of challenges exist, such as difficulties in the interrelated optical, carrier transport and recombination losses. Passivation layer (SiOx,1 AlOx5 and wide bandgap polymer6), silicon surface microstructures (random pyramids,7 nanowires8 and nanocones9), interface modification (LiF,10 PFN,2 PEO11and WO312) and antireflection layers (CuI, MoOx)13,14 have been adopted to partially alleviate these issues. Among all, the surface carrier recombination at the Si/PEDOT:PSS heterointerface is still one of primary issues which prevent the HSCs from reaching theoretic PCE limit.15 When PEDOT:PSS is deposited on the polished-side of silicon


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wafer, a large number of micropore defects are left at the Si/PEDOT:PSS heterointerface, especially when the textured Si substrate is used.16 In order to passivate this naked surface, the dielectric passivation layers (SiOx and AlOx) are usually used to suppress the surface carrier recombination. However, the thickness of these layers needs to be thin enough (usually < 3 nm) to ensure the holes tunneling through to the PEDOT:PSS layer. Under this thickness, these ultrathin dielectric layers do not provide the efficient surface passivation. Usually, minority charge carrier lifetime (τn) is only ca. 20 µs, far below the normal microsecond level.17,18 Therefore, a large number of photo-generated charge carriers are lost at the Si/PEDOT:PSS interface, resulting in severe degradation in PCE. Titanium oxide (TiO2) has been widely used in the photovoltaics, due to its outstanding features including large band gap, high transparency, good environment stability, high refractive index and electron mobility.19 Under ultraviolet (UV) irradiation, the generated electron-hole pairs are separated and move to the different regions of TiO2 nanoparticles, forming the photocurrent.20 Furthermore, the holes can oxidize OH- and H2O molecules absorbed on TiO2 surfaces into hydroxyl radicals (•OH), while the electrons in the conduction band can reduce the absorbed O2 molecules to form the superoxide (O2-) in both air and water. Subsequently, •OH as a highly reactive species is easily reduced by the ambient oxygen in a few seconds. In addition, O2- as the less reactive species is adsorbed on the TiO2 surfaces and remains several tens of seconds (lifetime > 50 s).21-23 Consequently, the progressive O2- leads to negative charge accumulation on the TiO2 surface under UV irradiation until the O2- species are saturated. The stored charge can revise the band offset at the surface of semiconductor, and further induce an electric field to passivate the silicon surface for retarding the carrier recombination.22,

24-26


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Herein, we would like to demonstrate a concept of photoinduced electric field from negative O2accumulation for the improved surface passivation at the Si/PEDOT:PSS interface. Different from PEDOT:PSS which has a low refractive index of ca. 1.4 and thus a poor antireflection effect, TiO2 film has a relatively high refractive index (typically n = 1.9-2.45) and low extinction coefficient(κ < 0.1 for λ > 350 nm), which is suitable for an antireflection coating (ARC) application.27 Thus, the TiO2 layer has been used to trap the sunlight in the Si/PEDOT:PSS system.28,29 In this study, a bilayer ARC of Polydimethylsiloxane (PDMS) and TiO2 was applied, where PDMS was introduced for the purpose of preventing the carriers from transporting to PEDOT:PSS layer, and TiO2 had a dual functions of light-trapping and producing the O2- species which induce a photoinduced electric field. The introduction of this photoactive ARC significantly improved the PCE of Si/PEDOT:PSS HSC from an average value of 12.01% to 15.01%, with a champion PCE of 15.51%. This photoinduced electric field not only provided a good field-effect passivation at the Si/PEDOT:PSS interface with the τn increased by 3 times, but also induced a positive shift of band edge of silicon, which enhanced the built-in potential (ψbi). Equipped with the photoactive ARC, the performance of HSCs was improved significantly, yielding the enhancement of 25 mV and 5.24 mA/cm2 for the open circuit voltage (Voc) and short circuit current density (Jsc), respectively. Therefore, the presence of TiO2 helps to boost the optical and electrical performance of front Si/PEDOT:PSS HSCs by the synergistic effect of light-trapping and field-effect passivation. Results and Discussion Photoinduced field passivated HSCs were fabricated by applying a transparent TiO2/PDMS ARC on as-processed Si/PEDOT:PSS heterojunction, as shown in Figure 1a (the SEM image of cross-section structure is presented in Figure S1). This solution-processable TiO2 film is used as


4

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the UV absorber to donate the electrons without effecting the light absorption of silicon, due to a large band gap (3.87 eV, Figure S2). The spectral match between TiO2 and Si absorption implies that the bilayer films act as a photoactive ARC without sacrificing the light harvesting for silicon. The O2- species are produced when the wavelength of incident light is shorter than 320 nm, and adsorbed on the TiO2 surface to be stored. The PDMS layer is adopted to prohibit the carriers of TiO2 film from transferring to the electronic circuit of HSC. Based on the photoinduced electric field from AM1.5 simulated sunlight, the Si/PEDOT:PSS HSC received an excellent photovoltaic performance: a champion PCE of 15.51% with a Voc of 632 mV, a Jsc of 31.98 mA/cm2 and a fill factor (FF) of 76.74%. Therefore, the photoactive ARC can help Si/PEDOT:PSS HSC to get an encouraging efficiency to enhance the competitiveness. Firstly, as an ARC, the optical performance of TiO2 film is evaluated comprehensively. The compacted TiO2 film made of nanoparticles with an average diameter of 4.01 nm has a relatively high refractive index of ca.2.1 (Figure S3). PDMS layer has a similar low refractive index with the PEDOT:PSS film. In order to ensure the optimal TiO2 thickness, a detailed theoretical simulation was implemented on a basis of the film thicknesses. Figure 2a shows the reflectance mapping of PEDOT:PSS/Si with the bilayer ARC, illustrating how the TiO2 film influence on the light antireflection. With increasing the thickness of TiO2 film, there is a large red shift of spectrum valley from around 500 nm to 1000 nm. In addition, the reflectance of short wavelength dramatically increases. For an optimal light absorption of silicon, the reflectance should be required to be low in visible wavelength range (400-900 nm). Therefore, a thin TiO2 film (1×1012 cm-2. Therefore, with the presence of surface charge carriers, the balance of energy banding under thermal equilibrium is broken and band edge of silicon bends to some extent, leading to a changed barrier height of built-in field and thus the photovoltaic performance (including Voc and PCE). This photoinduced negative carrier accumulation layer will be conducive to the efficiency development of Si/PEDOT:PSS HSC. Equipped with the light-trapping and photoinduced electric field of bilayer ARC, the photovoltaic performance of Si/PEDOT:PSS HSC will be improved significantly. From the results of Jloss, τn and ψbi, the thicknesses (< 39 nm) of TiO2 have a small influence on the performance of HSCs (Figure S9). However, Thicker TiO2 layer (>39 nm) increases reflective light to be a low photocurrent, resulted in a poor performance. Figure 6 shows the current density-voltage (J-V) characteristics of Si/PEDOT:PSS HSCs based on the different ARCs under AM 1.5G simulated sunlight illumination, and the photovoltaic parameters are summarized in Table 2. The Jsc values of HSCs only coated PDMS or TiO2 layer both increase, especially 3.89 mA/cm2 enhancement of TiO2 layer than 25.65 mA/cm2 of HSC without the ARC, corresponding to the simulated Jph results (Figure S4). However, the alone PDMS or TiO2 ARCs


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play a single role in the light-trapping to enhance the Jsc. Only combined with PDMS and TiO2 layers, this ARC has a synergistic effect of light-trapping and electric field to improve the photovoltaic performance. The HSC with the bilayer ARC receives an excellent efficiency of 15.01% with a Voc of 630 mV, a Jsc of 30.89 mA/cm2 and a FF of 77.45%, being UV part of simulated light in origin. Compared to the reference HSC, there is a 25 mV increment in Voc due to higher ψbi induced by this negative carrier accumulation layer. In addition, there is a 5.24 mA/cm2 enhancement of Jsc in the solar cell with the bilayer ARC. Two reasons for this Jsc improvement should be considered: 1) in light section, the bilayer ARC manage the light path to improve the light harvesting; 2) in electric section, the photoinduced electric field not only efficiently suppress the surface carrier recombination at the Si/PEDOT:PSS heterojunction but also enlarge the ψbi for high separation efficiency of photo-generation charge carriers, resulted in a high charge carrier collection efficiency. Additionally, we investigated the difference of performance of HSCs with bilayer ARC with and without the UV filter (Figure S10). After filtering the UV, fewer negative carriers are provided so that the performance of HSC reduces significantly. On the other hand, HSC without the PMDS/TiO2 ARC keeps the performance. Furthermore, prolonging the light duration, the photovoltaic performance of HSC with the PMDS/TiO2 ARC also increases to a large extent in Figure 7. However, the performance of HSC with the TiO2 ARC decays rapidly, especially in Voc, FF and PCE, because the holes of PEDOT:PSS layer is consumed by the photo-generated electrons of TiO2 layer.37,38 There is more 100 mV drop of Voc because of the low ψbi of Si/PEDOT:PSS from a low work function.37 In addition, the series resistance (Rs) of HSC with the TiO2 ARC increases due to the PEDOT:PSS conductivity decreasing, leading to a low FF.38 The HSC with the PDMS ARC almost maintains the photovoltaic performance under light soaking. The PDMS is an efficient


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encapsulated layer to prevent from being exposed to the atmosphere. The influence from the moisture absorption of PEDOT:PSS and the formation of oxide layer at the interface of Si/PEDOT:PSS can be prohibited, which develops the air stability of device. The performance of HSC without ARC become better firstly under light irradiation, however, after 150 s the performance start to decay drastically because of the influence of moisture and oxygen. Therefore, this photoactive ARC of PDMS/TiO2 bilayer is beneficial for improving the photovoltaic performance and stability of Si/ PEDOT:PSS HSCs. Conclusions In summary, we introduce a photoinduced electric field in the ARC, of which the charge carrier density and potential can be modulated by UV illumination (sunlight). This photoinduced electric field is particularly useful in the photovoltaic application, providing an efficient fieldeffect passivation at the silicon surface and enlarging the ψbi of Si/PEDOT:PSS HSCs. This photoactive ARC of PDMS/TiO2 bilayer also has a superior capability of light-trapping, similar to that of traditional random-pyramid structure. It is worth noting that the PCE of front-type Si/PEDOT:PSS HSC breaks through 15% only based on the simple photoactive ARC, which also can be applied in other solar cells that require an electric field to suppress the surface recombination or tune the ψbi value. The self-encapsulated, photoactive ARC with tunable electric field under UV irradiation displays a great potential for application in the development of photovoltaics and optoelectronics. Experimental TiO2 synthesis The solution of TiO2 nanoparticle dispersion was prepared as follows:39,40 a 470 µl tetrabutyl titanate was added dropwise into the 2.5 ml ethanol with 123 µl nitric acid under mild stirring of


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500 rpm. After 2h stirring, 114 µl deionized water was added into the mixture for the hydrolysis of tetrabutyl titanate and this reaction still went on 1h. Finally, the resulted solution was diluted by isopropanol to form the 0.127 M TiO2 solution. This transparent dispersion of TiO2 nanoparticles was ready for the spin-coating without centrifugation, washing and dispersing. Fabrication of Si/PEDOT:PSS HSCs The devices of Si/PEDOT:PSS HSCs were prepared as previously reported.1,11 One-side polished, n-type (100) silicon wafers (resistivity, 0.05 - 0.1 Ω•cm) with the thickness of 300 ± 15 µm were used as the substrates of devices. Firstly, the 20×20 mm2 square pieces were washed by the RCA cleaning process.1 The cleaned pieces were exposed to ambient atmosphere for 1 h. Then, the commercial PEDOT:PSS solution (Clevios PH1000) with the additives of the dimethylsulfoxide (DMSO, 5 wt%) and Triton X-100 (0.1 wt%) was spin-coated on the polished side of wafer at a speed of 3500 rpm and immediately thermally treated to form a 70 nm film at 140 °C for 10 min. A silver grid was prepared by the screen-printing with a low-temperature sintered silver paste, and then thermal treatment for 10 min to be an active area of 10×10 mm2. A PDMS (0.5 wt%) ethyl acetate solution was spin-coated above the PEDOT:PSS layer to form a 10 nm-thick dielectric layer. Then the transparent dispersion of TiO2 was continually spin-coated on the PDMS layer as an ARC, with 5 min thermal treatment at 140 °C. Finally, the rear electrode of Al was prepared by thermal evaporation with the thickness of 150 nm. The UV illumination was conducted by a 5 W UV LED lamp (254 nm). And the UV intensity was controlled by using neutral density filters and measured by using a UV power meter (TOPCON UVR-T1). For comprehensively comparing the optical-electric characteristics, three styles of reference HSCs were used: (a) Si/PEDOT:PSS, (b) PDMS/Si/PEDOT:PSS and (c) TiO2/Si/PEDOT:PSS.


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Simulation method In this study, we used the AFORS-HET software to solve Maxwell’s, drift-diffusion and Poisson equations for implement the optical and electric simulation of Si/PEDOT:PSS HSCs. The thicknesses of Si wafer, PEDOT:PSS and PDMS were fixed at 300 µm, 70 nm and 10 nm, respectively. Since these HSCs were considered as the stratified and planar structure, twodimensional model was used in the simulation. In the optical module, the perfectly matched layers were adopted on the front and rear sides to restrict the calculated domain. The wavelength range of 300-1150 nm was considered to implement the light response and absorption bandgap of HSCs. In the electrical module, the dynamic processes of charge carriers, including the photogenerated charge carrier transport, recombination and collection, were carried out under the AM 1.5G sunlight illumination. Additionally, the photoelectric constants (the refractive index, electron and hole mobility, minority charge carrier lifetime and recombination velocity, work function and band gap, etc.) could be found in publications elsewhere.1,2,36 Characterization A particle size analyzer (Zetasizer Nano ZS, Malvern) was used to measure the diameter of TiO2 nanoparticles in solution. The transmittance of TiO2 film was measured by a UV-visible spectrophotometer (Lambda 950, Perkin-Elmer), and reflectance was measured by a reflectance analyzer (HELIOS LAB-RE, AudioDevGmbH). EPR (Bruker EMX-10/12 plus) was used to examine the paramagnetic species in TiO2 layer at 2 K temperature under the O2-rich vacuum of 10-3 mbar. Kelvin probe studies were performed to analyze the ϕs by using a Digital Instruments Dimension 3100 Nanoscope IV, with the conductive tapes to ensure a good ohmic contact to substrate. C-V curves of PEDOT:PSS/PDMS/Ag accompanied with TiO2 film (MOS structure) and HSCs were measured by a Parameter Analyzer (Keithley 4200-SCS) at a signal frequency of


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1 kHz. τn values of wafers were measured by a photoconductance lifetime tester (WCT-120, Sinton, USA) without or with UV irradiation. J-V characteristics of HSCs were recorded with a digital source meter (Keithley, USA) under a simulated AM 1.5G sunlight (100 mW/cm2) illumination provided by a xenon lamp (Oriel, USA). A standard multicrystalline silicon solar cell (Oriel, model 91150V) calibrated the intensity of simulated irradiation. The front of solar cells were shielded by the opaque mask with an open area of 7×8 mm2. And the temperature was controlled at 25 ± 0.5 ºC during the measurements. EQE system used a 300 W xenon light source with a spot size of 1×3 mm2, which was calibrated with a silicon photodetector also from Newport. ASSOCIATED CONTENT Supporting Information. SEM image of cross-section; Absorption spectrum, photonic band gap and transmittance of TiO2 thin film; diameter distribution and XRD pattern of TiO2 nanoparticles; refractive index; simulated photocurrent density of HSCs with TiO2 ARC; schematic and C-V of MOS structure curves with UV different intensities; minority charge carrier lifetime as a function of thicknesses with the various duration of UV irradiation; energy band structure and built-in potential; J-V curves of HSCs as a function of TiO2 film thicknesses and UV filter. AUTHOR INFORMATION Corresponding Author *E-mails: [email protected]; [email protected]; [email protected].


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ACKNOWLEDGMENT We acknowledge the Steady High Magnetic Field Facility in High Magnetic Field Laboratory, Chinese Academy of Sciences for the EPR measurement. This work was supported by the National Natural Science Foundation of China (Grant No. 21403262 and No. 61574145), Natural Science Foundation of Zhejiang Province (Grant No. LR16F040002 and No. LY15F040003), Major Project and Key S&T Program of Ningbo (Grant No. 2016B10004), and International S&T Cooperation Program of Ningbo (Grant No. 2015D10021 and No. 2016D10011).

(b) 2

Current density (mA/cm )

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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35 30 25 20 15 10

Voc = 632 mV 2

Jsc = 31.98 mA/cm FF = 76.74% PCE = 15.51%

5 0 0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Voltage (V)

Figure 1. (a) Schematic image of a Si/PEDOT:PSS HSC with a TiO2/PDMS ARC. (b) J-V curves of the champion Si/PEDOT:PSS HSC with a photoactive ARC under AM 1.5G simulated sunlight.


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80

(d)

Si Si+PEDOT Si+PEDOT+PDMS+TiO2

60 40 20 0

1.0 0.8

Random pyramids Random pyramids+SiNx

EQE (%)

(c) Reflectance (%)

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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0.6 PEDOT:PSS +PDMS +TiO2

0.4 0.2

400

600 800 1000 Wavelength (nm)

1200

0.0

+PDMS+TiO2

400

600

800

1000

1200

Wavelength (nm)

Figure 2. (a) Simulated reflectance and (b) Optical photocurrent losses of PEDOT:PSS/Si HSCs with the bilayer ARC based on the various thicknesses of TiO2 film. (c) Reflectance of polished-side silicon wafer with the various ARCs (experimental data are represented by dots and the data of fit linear are represented by line). (d) EQE curves of Si/PEDOT:PSS HSCs without and with the different ARCs.


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(c) Capacitance (nF)

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3.0 2.5 2.0 1.5 1.0 0.5 -0.6

w/o UV UV on UV 5 s UV 30 s UV 60 s UV 300s -0.4

-0.2

0.0

0.2

0.4

0.6

Voltage (V)

Figure 3. (a) EPR spectra of TiO2 film after 1 min with and without UV illumination at 2 K. (b) Surface potential images of TiO2 film after the different durations of UV illumination. (c) Typical C-V curves of PEDOT:PSS/PDMS/Ag accompanied with TiO2 film after the different durations of UV illumination, right figure is equivalent circuit model.


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(a)

(b)

80

Light on

Light off

120

60

Lifetime (µ s)

70 Lifetime (µs)

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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PEDOT PEDOT+PDMS PEDOT+TiO2

50

PEDOT+PDMS+TiO2

40

100 80


60

PEDOT+PDMS+TiO2

40 30

20 0

100

200 Time (s)

300

400

0

1

2

3 2

Light intensity (mW/cm )

Figure 4. Minority charge carrier lifetimes of n-type silicon based on the different layer as a function of UV irradiation time (a) and intensity (b).


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Figure 5. (a) Energy band structure of Si/PEDOT:PSS heterojunction based on the negative surface carriers. (b) Photovoltaic performance (Voc and PCE) of HSCs as a function of the negative surface carrier density.


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35 2 Current density (mA/cm )

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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30 25 20


15 10 5 0 0.0

PEDOT+PDMS+TiO2 0.1

0.2

0.3

0.4

0.5

0.6

0.7

Voltage (V)

Figure 6. J-V curves of Si/PEDOT:PSS HSCs based on the different ARCs.


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(a)

(b)

0.70

0.55

PEDOT +PDMS +TiO2

0.50 0.45

(c)

Jsc (mA/cm2)

Voc (mV)

0.60

0.40

0

100 200 300 400 light irradiation duration (s)

PEDOT +PDMS +TiO2

24

0

+PDMS+TiO2 100 200 300 400 light irradiation duration (s)

500

(d) 16 14 PCE (%)

72 68

56

26

20

500

76

60

28

22

+PDMS+TiO2

80

64

32 30

0.65

FF (%)

PEDOT +PDMS +TiO2

12 PEDOT +PDMS +TiO2

10 8

+PDMS+TiO2 0 100 200 300 400 light irradiation duration (s)

(e)

12

500

6

0

+PDMS+TiO2 100 200 300 400 light irradiation duration (s)

500

PEDOT +PDMS +TiO2

)

-2

Series resistance (Ω cm

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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10

+PDMS+TiO2

8 6 4 2

0

100 200 300 400 light irradiation duration (s)

500

Figure 7. Photovoltaic performance including Voc (a), Jsc (b), FF (c), PCE (d) and Rs (e) of Si/PEDOT:PSS HSCs with the different ARCs under the various duration of light irradiation.


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Table 1. Charge density and electric field of TiO2 film under UV irradiation from Kelvin probe and C-V measurements. UV irradiation

Qsurf

Esurf

Qvol

Evol

(1 mW/cm2)

(C•cm-2)

(N•C-1)

(C•cm-2)

(N•C-1)

0s

5.89×1014

2.22×103

7.49×1014

2.82×103

60 s

6.36×1014

2.40×103

1.03×1015

3.88×103

300 s

6.95×1014

2.62×103

1.12×1015

4.28×103


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ACS Nano

Table 2. Photovoltaic properties of Si/PEDOT:PSS HSCs with the different ARCs under simulated AM 1.5G illumination. Devices

Voc (mV)

Jsc (mA/cm2)

FF(%)

PCE(%)

PEDOT

604±3

25.65±0.52

77.43±0.48

12.01±0.54

PEDOT+PDMS

605±2

26.62±0.46

76.47±0.57

12.32±0.59

PEDOT+TiO2

602±5

29.48±0.74

75.66±0.69

13.44±0.77

PEDOT+PDMS+TiO2

630±5

30.89±0.61

77.45±0.53

15.01±0.58


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A photoinduced electric field in the antireflective coating produces the efficient surface passivation and revises the band offset of silicon. 265x187mm (96 x 96 DPI)


Photoinduced Field-Effect Passivation from Negative Carrier

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