Representative 4T PVK/Si tandem SCs based on a homojunction Si bottom SC as a function of the type of top SC structures such as n-i-p or p-i-n. This was applied to the bottom SC of each of the PERL SCs to make a 4T PVK/Si tandem SC and reported an efficiency of 26.7%.
I NTRODUCTION
- State of the Photovoltaic Industry
- Physics of Solar Cells
- L IMITATIONS OF S INGLE J UNCTION S OLAR C ELL
- M ULTIJUNCTION S OLAR C ELLS
- What is the Multijunction Solar Cells?
- Various types of Multijunction Solar Cells
- P EROVSKITE /S ILICON T ANDEM S OLAR C ELLS
- O UTLINE OF T HIS D ISSERTATION
- R EFERENCES
The cause of the initial optical loss of monolithic PVK/Si tandem SCs is analyzed in Figure 2.5. Simulated EQE data of the monolithic PVK/Si tandem SC with different PVK band gaps and thicknesses. Summary of the device performance of PVK SCs with (FAPbI3)1-x(MAPbBr3)x PVK films using different doping ratios deposited on poly(triarylamine) (PTAA).
To evaluate the stability of the PVK/Si tandem SC, glass-on-glass encapsulation was applied, as shown in Figure 4.17a.
O PTICAL S IMULATION TO O PTIMIZE P EROVSKITE /S ILICON T ANDEM S OLAR C ELLS
E XPERIMENTAL M ETHODS
- Measurement of Refractive Indices and Absorption Coefficients
- Characterization Methods of Optical Simulation
The values of PDMS, ZnO nps, PVK, Si, Al and Ag mentioned in the literature are specified in Table 2.1. However, any 1D or 2D texture with lateral and vertical features in the micrometer or millimeter range can be applied to either side of the thin layer. The lighting conditions, the exact structure of the simulated device, and the optical properties of the materials used in the device comprised the main input parameters.
The texture was assumed to be periodic and the boundary condition was applied at the lateral boundary of the ray tracing domain.
R ESULTS AND D ISCUSSION
- Device Design to Optimize Perovskite/Silicon Tandem Solar Cell
Through the current density, voltage and fill factor in the tandem SC, the change in the efficiency based on the current density of the tandem SC was also predicted (Figure 2.6b). Based on the empirical observation, it is noted that when the band gap of the PVK was 1.65 eV, the voltage of the semi-transparent PVK SC was 1.17 V. of the Si SC due to absorption of the short wavelength region by the filter was empirically about 0.02 V.
Using the above assumptions, the JSC, VOC, FF, and efficiency at the current matching point of the monolithic/PVK tandem SC predicted by optical simulation were 16.84 mA/cm2, 1.76 V, 80%, and 23.71%, respectively.
C ONCLUSION
In addition, PCBM caused an optical loss due to light absorption in the short wavelength region; the loss of current density was 1.85 mA/cm2. The reasons for the largest optical loss in the monolithic PVK/Si tandem SCs are a surface reflection of tandem SCs,17 light absorption in the long wavelength region of the IZO layer,21 and light absorption in the short wavelength region of the PCBM. layer.22 The current density losses of the other layers, apart from the main optical loss-inducing layers mentioned above, are summarized in Table 2.2. When the PVK thickness was 500 nm at 1.65 eV, the current density corresponding to the current in the monolithic PVK/Si tandem SC was predicted to be 16.84 mA/cm2 (Figure 2.6a).
As the optical loss of the functional layers is improved with the development of technology and PERC is introduced, the current density of the tandem SC increases, so the efficiency is also expected to improve.
R EFERENCES
As shown in Figure 3.12, as the amount of MACl increased, the grain size of PVK continued to increase. Summary of the device performance of PVK/Si tandem devices with (MAPbI3)1- x(MAPbBr3)x PVK films using different doping ratios on PEDOT:PSS. In addition, the current density of the Si substrate SC differs slightly depending on the band gap and the thickness of the PVK.
Schematic of the current matching for monolithic PVK/Si tandem SC, using a semi-transparent PVK SC with a matched band gap and PVK film thickness.
S INGLE CELL FOR TANDEM SOLAR CELL : PEROVSKITE TOP CELLS AND SILICON
E XPERIMENTAL M ETHODS
- Experimental Details of Perovskite Top Cell
- Experimental Details of Silicon Bottom Cell
- Characterization Methods
In the case of the pyramid-textured silicon SC from the back side, the silicon surface was etched with KOH/IPA solution. The bias voltage for steady-state measurements was chosen as the average of the maximum power point voltage of the J-V measurement. Cell EQE was measured using a Quantx-300 incident-photon-to-current conversion measurement system (Newport) with a cutoff frequency of 4 Hz.
To measure the EQE of the perovskite subcell, the silicon subcell was saturated using a white bias.
R ESULTS AND D ISCUSSION
- Wide Band Gap Engineering of Top Cells
As shown in Figure 3.11a, we used XRD to analyze the crystallinity of the MACl-doped PVK thin film. As the concentration of MACl increases, the cation composition ratio of CS/FA/MA changes. Furthermore, the ratio of the I/Br halide compound composition changes as the amount of Cl increases.
This reduced the non-radiative recombination, due to the passivation effect by stacking 2D PVK on the surface defects of the 3D PVK thin film.
C ONCLUSION
If this is applied to the above equation, the refractive index of Si-nitride is approx. 2.98. However, the maximum value of the refractive index that can be realized using PECVD in our laboratory is 2.84. It was calculated that 66 nm is the thickness required to minimize the reflectance at 750 nm when the SiNx refractive index of 2.84 was introduced (Figure 3.27b).
Finally, the bottom Si cell design for the tandem SC was fabricated using graded refractive index matching of the tandem SC to reduce light loss.
R EFERENCES
Summary of Si SC as a function of doping temperature. a) Schematic of Si SC with a textured back surface. Finally, a tandem SC based on a PERC Si SC is fabricated from p-Si homojunction SCs, which occupy the mainstream of the Si SC market. Summary of device performance of uniform monolithic PVK/Si SCs to enhance absorption in the long wavelength region, using a 66 nm SiNx layer with a refractive index of 2.84.
Tandem SC based on PERC cells was fabricated by applying all tandem element technology except refractive index scale matching. Finally, a tandem SC based on a PERC Si SC was fabricated among the p-Si homojunction SCs occupying the mainstream of the Si SC market. Responsible for optical design for monolithic perovskite/CIGS tandem solar cell optimization with optical simulation.
MONOLITHIC PEROVSKITE / SILICON TANDEM SOLAR CELL
E XPERIMENTAL M ETHODS
- Experimental Details of Monolithic Perovskite/Silicon Tandem Solar Cell 118
- Characterization Methods
Under heat treatment at 850 °C for 2 min using an RTA system to control the doping level, the n + emitter was formed with a sheet resistance of 100 Ω/sq on the front side, and the p + Al-BSF was formed on the back side of the Si wafers . HTLs, such as PTAA (Sigma-Aldrich, 2 mg/ml in chlorobenzene (CB)), were spin-coated onto the ITO of the Si bottom cell with UV treatment at 4000 rpm and annealed at 100 °C in 10 minutes. During this period, 300 μL of ethyl acetate was poured onto the rotating substrate 20 s before the end of the program.
The J-V characteristics of the SCs were determined using a Keithley 4200 source measurement unit under simulated AM 1.5G light (Oriel Sol3A Solar Simulator) at 100 mW cm−2, with a metal orifice and a scan rate of 5 mV s-1 in the direction from the no-load voltage to the short-circuit current.
R ESULTS AND D ISCUSSION
- Current Matching of Tandem Solar Cell
- Recombination Layers of Tandem Solar Cell
- Graded Refractive Index Matching Designs for Tandem Solar Cell
- Stability Test
Therefore, the most accurate method to perform current matching by EQE analysis is to apply the bandgap and thickness of the PVK to the actual device in the range predicted by optical design, as shown in Figure 4.4. In Figure 4.5a and Figure 4.5b, the current matching point of the tandem SC was determined by EQE analysis based on the change in the bandgap and thickness of the PVK applied to the ITO-finished Si-bottom SC. As shown in Figure 4.14a, to minimize the optical loss in the 750–1200 nm wavelength band, where the Si bottom SC starts to absorb light, the refractive index of each functional layer of the tandem SC is considered by the indices of the PVK top SC and Si under SC.
Likewise, this was the result of the increased stability of the PVK structure due to the addition of Cs.
C ONCLUSION
In this case, since the refractive index of air is 1, the refractive index of the SiNx layer is 2.84, resulting in a reflection loss due to the difference in refractive index. If penetration is prevented, more than 90% of the initial efficiency is expected to be retained, even after 1000 hours. Moreover, tandem SCs are fabricated based on PERC SC, which currently occupies the mainstream of the SC market.
Thus, it is expected that tandem SCs can be produced without major replacement of the infrastructure of the existing SC industry.
R EFERENCES
Zhao, Y.; Zhang, X., Monolithic Perovskite/Silicon-Heterojunction Tandem Solar Cells with Open Circuit Voltage Above 1.8 V. Uraoka, Y.; Ito, S., Interface Optoelectronics Engineering for Mechanically Stacked Tandem Solar Cells Based on Perovskite and Silicon. 7 "Development of efficient, scalable and stable perovskite solar cells for commercial transparent tandem solar cells" Ministry of Science and ICT.
Development of high-efficiency (≥25%) crystalline monolithic tandem solar cells of Si/Perovskite” Ministry of Trade, Industry and Energy.
S UMMARY AND S UGGESTIONS FOR F UTURE W ORKS
S UGGESTIONS FOR F UTURE W ORKS
Although the efficiency of 2T PVK/Si tandem SCs is higher than 29%, which is the theoretical limit of Si single-junction SCs, and the rapid development of large-scale deposition processes for PVK layers is promising, the cost of PVK /Si promising. tandem SCs should be considered for commercialization. According to the recently reported cost analysis for PVK SCs and PVK/Si tandem SCs, the process equipment and maintenance costs of the evaporation process can be low with high throughput in mass production. Although the above obstacles in the commercialization of PVK/Si tandem SCs have been discussed in detail in the literature and many potential solutions have been proposed, the high processing temperature of top metal lattice metallization of conventional Si SCs has been overlooked.
In the current PVK/Si tandem SC research, it is essential that the PVK upper SC has a wide bandgap because it is based on the monofacial Si lower SC.
R EFERENCES
8 "Two-Terminal Mechanical Perovskite/Silicon Tandem Solar Cells with Transparent Conductive Adhesives." V Young Choi, Chan Ul Kim, Won Jin Park, Hyungmin Lee, Myoung Hoon Song, Kuen Kee Hong, Sang Il Seok and Kyoung Jin Choi. Solar Cells Using Self-Assembled Oxide and Their Fabrication Method” Chan Ul Kim, Kyoung Jin Choi, Min Joo Park, Sung Bum Kang, Myung Hoon Jeong, In Young Choi. Fabrication of High Efficiency Hybrid Solar Cells Based on SiNWs/PEDOT:PSS” Chan Ul Kim, Myung Hoon Jeong, Ja Young Won and Kyoung Jin Choi.
Failure Analysis of PEDOT:PSS/n-Si Hybrid Solar Cells During Long-Term Stability Test” Chan Ul Kim, Ja Young Won, and Kyoung Jin Choi.
