Preparation and measurement of highly efficient a‐Si:H single junction solar cells and the advantages of μc‐SiOx:H n‐layers

Reducing the optical losses and increasing the reflection while maintaining the function of doped layers at the back contact in solar cells are important issues for many photovoltaic applications. One approach is to use doped microcrystalline silicon oxide (μc‐SiO_x:H) with lower optical absorption in the spectral range of interest (300 nm to 1100 nm). To investigate the advantages, we applied the μc‐SiO_x:H n‐layers to a‐Si:H single junction solar cells. We report on the comparison between amorphous silicon (a‐Si:H) single junction solar cells with either μc‐SiO_x:H n‐layers or non‐alloyed silicon n‐layers. The origin of the improved performance of a‐Si:H single junction solar cells with the μc‐SiO_x:H n‐layer is identified by distinguishing the contributions because of the increased transparency and the reduced refractive index of the μc‐SiO_x:H material. The solar cell parameters of a‐Si:H solar cells with both types of n‐layers were compared in the initial state and after 1000 h of light soaking in a series of solar cells with various absorber layer thicknesses. The measurement procedure for the determination of the solar cell performance is described in detail, and the measurement accuracy is evaluated and discussed. For an a‐Si:H single junction solar cell with a μc‐SiO_x:H n‐layer, a stabilized efficiency of 10.3% after 1000 h light soaking is demonstrated. Copyright © 2015 John Wiley & Sons, Ltd.     

Boron‐doped hydrogenated silicon carbide alloys containing silicon nanocrystallites for highly efficient nanocrystalline silicon thin‐film solar cells

Boron‐doped hydrogenated silicon carbide alloys containing silicon nanocrystallites (p‐nc‐SiC:H) were prepared using a plasma‐enhanced chemical vapor deposition system with a mixture of CH₄, SiH₄, B₂H₆ and H₂ gases. The influence of hydrogen dilution on the material properties of the p‐nc‐SiC:H films was investigated, and their roles as window layers in hydrogenated nanocrystalline silicon (nc‐Si:H) solar cells were examined. By increasing the R_H (H₂/SiH₄) ratio from 90 to 220, the Si―C bond density in the p‐nc‐SiC:H films increased from 5.20 × 10¹⁹ to 7.07 × 10¹⁹/cm³, resulting in a significant increase of the bandgap from 2.09 to 2.23 eV in comparison with the bandgap of 1.95 eV for p‐nc‐Si:H films. For the films deposited at a high R_H ratio, the Si nanocrystallites with a size of 3–15 nm were formed in the amorphous SiC:H matrix. The Si nanocrystallites played an important role in the enhancement of vertical charge transport in the p‐nc‐SiC:H films, which was verified by conductive atomic force microscopy measurements. When the p‐nc‐SiC:H films deposited at R_H = 220 were applied in the nc‐Si:H solar cells, a high conversion efficiency of 8.26% (V_oc = 0.53 V, J_sc = 23.98 mA/cm² and FF = 0.65) was obtained compared to 6.36% (V_oc = 0.44 V, J_sc = 21.90 mA/cm² and FF = 0.66) of the solar cells with reference p‐nc‐Si:H films. Further enhancement in the cell performance was achieved using p‐nc‐SiC:H bilayers consisting of highly doped upper layers and low‐level doped bottom layers, which led to the increased conversion efficiency of 9.03%. Copyright © 2015 John Wiley & Sons, Ltd.     

Simulation and fabrication of heterojunction silicon solar cells from numerical computer and hot‐wire CVD

In this paper, we will present a Pc1D numerical simulation for heterojunction (HJ) silicon solar cells, and discuss their possibilities and limitations. By means of modeling and numerical computer simulation, the influence of emitter‐layer/intrinsic‐layer/crystalline‐Si heterostructures with different thickness and crystallinity on the solar cell performance is investigated and compared with hot wire chemical vapor deposition (HWCVD) experimental results. A new technique for characterization of n‐type microcrystalline silicon (n‐µc‐Si)/intrinsic amorphous silicon (i‐a‐Si)/crystalline silicon (c‐Si) heterojunction solar cells from Pc1D is developed. Results of numerical modeling as well as experimental data obtained using HWCVD on µc‐Si (n)/a‐Si (i)/c‐Si (p) heterojunction are presented. This work improves the understanding of HJ solar cells to derive arguments for design optimization. Some simulated parameters of solar cells were obtained: the best results for J_sc = 39·4 mA/cm², V_oc = 0·64 V, FF = 83%, and η = 21% have been achieved. After optimizing the deposition parameters of the n‐layer and the H₂ pretreatment of solar cell, the single‐side HJ solar cells with J_sc = 34·6 mA/cm², V_oc = 0·615 V, FF = 71%, and an efficiency of 15·2% have been achieved. The double‐side HJ solar cell with J_sc = 34·8 mA/cm², V_oc = 0·645 V, FF = 73%, and an efficiency of 16·4% has been fabricated. Copyright © 2009 John Wiley & Sons, Ltd.     

Progress of Thin‐Film Silicon Photovoltaic Technologies in SANYO

Methods to achieve a good balance among a high conversion efficiency, a large panel size and a high deposition rate of µc‐Si:H for mass production are shown here. For this purpose, an original technology called the Localized Plasma Confinement CVD (LPC‐CVD) method is investigated. Using know‐how from this method, an amorphous silicon/microcrystalline silicon (µc‐Si:H) solar panel, whose size is Gen. 5.5 (1100 mm × 1400 mm) and whose µc‐Si:H deposition rate is 2.4 nm/s, with a conversion efficiency of 11.1% (V_oc = 161.7 V, I_sc = 1.46 A, FF = 72.4%, P_max = 171 W) is obtained. It is also experimentally confirmed that the value is equivalent to 10.0% of stabilized efficiency. Various reliability tests that conform to IEC standards have been performed for solar modules. It has been shown that the solar modules adapt to the major categories of IEC standards. Copyright © 2011 John Wiley & Sons, Ltd.     

Multi‐crystalline Si solar cells with very fast deposited (180 nm/min) passivating hot‐wire CVD silicon nitride as antireflection coating

Hot‐wire chemical vapor deposition (HWCVD) is a promising technique for very fast deposition of high quality thin films. We developed processing conditions for device‐ quality silicon nitride (a‐SiN_x:H) anti‐reflection coating (ARC) at high deposition rates of 3 nm/s. The HWCVD SiN_x layers were deposited on multicrystalline silicon (mc‐Si) solar cells provided by IMEC and ECN Solar Energy. Reference cells were provided with optimized parallel plate PECVD SiN_x and microwave PECVD SiN_x respectively. The application of HWCVD SiN_x on IMEC mc‐Si solar cells led to effective passivation, evidenced by a V_oc of 606 mV and consistent IQE curves. For further optimization, series were made with HW SiN_x (with different x) on mc‐Si solar cells from ECN Solar Energy. The best cell efficiencies were obtained for samples with a N/Si ratio of 1·2 and a high mass density of >2·9 g/cm³. The best solar cells reached an efficiency of 15·7%, which is similar to the best reference cell, made from neighboring wafers, with microwave PECVD SiN_x. The IQE measurements and high V_oc values for these cells with HW SiN_x demonstrate good bulk passivation. PC1D simulations confirm the excellent bulk‐ and surface‐passivation for HW SiN_x coatings. Interesting is the significantly higher blue response for the cells with HWCVD SiN_x when compared to the PECVD SiN_x reference cells. This difference in blue response is caused by lower light absorption of the HWCVD layers (compared to microwave CVD; ECN) and better surface passivation (compared to parallel plate PECVD; IMEC). The application of HW SiN_x as a passivating antireflection layer on mc‐Si solar cells leads to efficiencies comparable to those with optimized PECVD SiN_x coatings, although HWCVD is performed at a much higher deposition rate. Copyright © 2007 John Wiley & Sons, Ltd.     

Optimization of interdigitated back contact silicon heterojunction solar cells: tailoring hetero‐interface band structures while maintaining surface passivation

Interdigitated back contact silicon heterojunction (IBC‐SHJ) solar cells have the potential for high open circuit voltage (V_OC) due to the surface passivation and heterojunction contacts, and high short circuit current density (J_SC) due to all back contact design. Intrinsic amorphous silicon (a‐Si:H) buffer layer at the rear surface improve the surface passivation hence V_OC and J_SC, but degrade fill factor (FF) from an “S” shape J–V curve. Two‐dimensional (2D) simulation using “Sentaurus device” demonstrates that the low FF is related to the valence band offset (energy barrier) at the hetero‐interface. Three approaches to the buffer layer are suggested to improve the FF: (1) reduced thickness, (2) increased conductivity, and/or (3) reduced band gap. Experimental IBC‐SHJ solar cells with reduced buffer thickness (<5 nm) and increased conductivity with low boron doping significantly improves FF, consistent with simulation. However, this has only marginal effect on efficiency since J_SC and V_OC also decrease due to poor surface passivation. A narrow band gap a‐Si:H buffer layer improves cell efficiency to 13.5% with unoptimized passivation quality. These results demonstrate that tailoring the hetero‐interface band structure is critical for achieving high FF. Simulations predicts that efficiences >23% are possible on planar devices with optimized pitch dimensions and achievable surface passivation, and 26% with light trapping. This work provides criterion to design IBC‐SHJ solar cell structures and optimize cell performance. Copyright © 2010 John Wiley & Sons, Ltd.     

High‐efficiency µc‐Si solar cells made by very high‐frequency plasma‐enhanced chemical vapor deposition

Microcrystalline silicon‐based single‐junction p–i–n solar cells have been fabricated by very high‐frequency plasma enhanced chemical vapor deposition using a showerhead cathode at high pressures and under silane depletion conditions. The i‐layers are made near the transition from amorphous to crystalline. It was found that, especially at high crystalline fractions, the open‐circuit voltage and fill factor are very sensitive to the morphology of the substrate. At an i‐layer deposition rate 0·45 nm/s, we have measured a stabilised efficiency of 10% (V_oc = 0·52 V, FF = 0·74) for a cell made on texture‐etched ZnO:Al. The performance is stable under light soaking. The defect density of the absorber layer is in the 10¹⁵ cm⁻³ range. In spite of the presence of oxygen contamination, good electrical properties and good infrared cell response are obtained. Copyright © 2006 John Wiley & Sons, Ltd.     

The Relation Between Open‐Circuit Voltage and the Onset of Photocurrent Generation by Charge‐Transfer Absorption in Polymer : Fullerene Bulk Heterojunction Solar Cells

Photocurrent generation by charge‐transfer (CT) absorption is detected in a range of conjugated polymer–[6,6]‐phenyl C₆₁ butyric acid methyl ester (PCBM) based solar cells. The low intensity CT absorption bands are observed using a highly sensitive measurement of the external quantum efficiency (EQE) spectrum by means of Fourier‐transform photocurrent spectroscopy (FTPS). The presence of these CT bands implies the formation of weak ground‐state charge‐transfer complexes in the studied polymer–fullerene blends. The effective band gap (E_g) of the material blends used in these photovoltaic devices is determined from the energetic onset of the photocurrent generated by CT absorption. It is shown that for all devices, under various preparation conditions, the open‐circuit voltage (V_oc) scales linearly with E_g. The redshift of the CT band upon thermal annealing of regioregular poly(3‐hexylthiophene):PCBM and thermal aging of poly(phenylenevinylene)(PPV):PCBM photovoltaic devices correlates with the observed drop in open‐circuit voltage of high‐temperature treated versus untreated devices. Increasing the weight fraction of PCBM also results in a redshift of E_g, proportional with the observed changes in V_oc for different PPV:PCBM ratios. As E_g corresponds with the effective bandgap of the material blends, a measurement of the EQE spectrum by FTPS allows us to measure this energy directly on photovoltaic devices, and makes it a valuable technique in the study of organic bulk heterojunction solar cells.     

Silicon germanium active layer with graded band gap and µc-Si:H buffer layer for high efficiency thin film solar cells

We investigated solar cells with graded band gap hydrogenated amorphous silicon germanium active layer and hydrogenated microcrystalline silicon buffer layer at the interface of intrinsic and n-type doped layer. A significantly improved, 10.4% device efficiency was observed in this type of single junction solar cell. The intrinsic type microcrystalline silicon buffer layer is thought to play dual roles in the device; as a crystalline seed-layer for growth of n-type hydrogenated microcrystalline silicon layer and helping efficient electron collection across the i/n interface. Based on these, an enhancement in cell parameters such as the open-circuit voltage (V_oc), and fill factor (FF) was observed, where the FF and V_oc reaches up to 69% and 0.85 V respectively. Our investigation shows a simple way to improve device performance with narrow-gap silicon germanium active layer in solar cells in comparison to the conventionally constant band gap device structure.     

High‐Performance Planar Solar Cells Based On CH3NH3PbI3‐xClx Perovskites with Determined Chlorine Mole Fraction

Solution‐processable hybrid perovskite solar cells are a new member of next generation photovoltaics. In the present work, a low‐temperature two‐step dipping method is proposed for the fabrication of CH₃NH₃PbI_3‐xCl_x perovskite films on the indium tin oxide glass/poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) substrate. The bandgaps of the CH₃NH₃PbI_3‐xCl_x perovskite films are tuned in the range between 1.54 and 1.59 eV by adjusting the PbCl₂ mole fraction (n_Cl/(n_Cl + n_I)) in the initial mixed precursor solution from 0.10 to 0.40. The maximum chlorine mole fraction measured by a unique potentiometric titration method in the produced CH₃NH₃PbI_3‐xCl_x films can be up to 0.220 ± 0.020 (x = 0.660 ± 0.060), which is much higher than that produced by a one‐step spin‐coating method (0.056 ± 0.015, x = 0.17 ± 0.04). The corresponding solar cell with the CH₃NH₃PbI_2.34±0.06Cl_0.66±0.06 perovskite film sandwiched between PEDOT:PSS and C₆₀ layers exhibits a power conversion efficiency as high as 14.5%. Meanwhile, the open‐circuit potential (V_oc) of the device reaches 1.11 V, which is the highest V_oc reported in the perovskite solar cells fabricated on PEDOT:PSS so far.     

SnO2‐C60 Pyrrolidine Tris‐Acid (CPTA) as the Electron Transport Layer for Highly Efficient and Stable Planar Sn‐Based Perovskite Solar Cells

For solar cell applications, Sn‐based hybrid perovskites have drawn particular interest due to their environmental friendliness. Here, a thin layer of C₆₀ pyrrolidine tris‐acid (CPTA) is found essential for achieving high efficiency with planar solar cells of Sn‐based perovskites. As a result, a power conversion efficiency of 7.40% is achieved for {en}FASnI₃ solar cells with a planar n–i–p architecture, and the device exhibits excellent stability in air. For the first time, highly efficient Sn‐based hybrid perovskite solar cells on n–i–p architecture are achieved. A V_oc of 0.72 V is highlighted as the highest V_oc ever reported for FASnI₃ solar cells.     

20.0% Efficiency Si Nano/Microstructures Based Solar Cells with Excellent Broadband Spectral Response

Spectral response of solar cells determines the output performance of the devices. In this work, a 20.0% efficient silicon (Si) nano/microstructures (N/M‐Strus) based solar cell with a standard solar wafer size of 156 × 156 mm² (pseudo‐square) has been successfully fabricated, by employing the simultaneous stack SiO₂/SiN_x passivation for the front N/M‐Strus based n⁺‐emitter and the rear surface. The key to success lies in the excellent broadband spectral responses combining the improved short‐wavelength response of the stack SiO₂/SiN_x passivated Si N/M‐Strus based n⁺‐emitter with the extraordinary long‐wavelength response of the stack SiO₂/SiN_x passivated rear reflector. Benefiting from the broadband spectral response, the highest open‐circuit voltage (V_oc) and short‐circuit current density (J_sc) reach up to 0.653 V and 39.0 mA cm^?2, respectively. This high‐performance screen‐printed Si N/M‐Strus based solar cell has shown a very promising way to the commercial mass production of the Si based high‐efficient solar cells.     

Current transport studies of amorphous n/p junctions and its application in a‐Si:H/HIT‐type tandem cells

This paper presents an understanding of the fundamental carrier transport mechanism in hydrogenated amorphous silicon (a‐Si:H)‐based n/p junctions. These n/p junctions are, then, used as tunneling and recombination junctions (TRJ) in tandem solar cells, which were constructed by stacking the a‐Si:H‐based solar cell on the heterojunction with intrinsic thin layer (HIT) cell. First, the effect of activation energy (E_a) and Urbach parameter (E_u) of n‐type hydrogenated amorphous silicon (a‐Si:H(n)) on current transport in an a‐Si:H‐based n/p TRJ has been investigated. The photoluminescence spectra and temperature‐dependent current–voltage characteristics in dark condition indicates that the tunneling is the dominant carrier transport mechanism in our a‐Si:H‐based n/p‐type TRJ. The fabrication of a tandem cell structure consists of an a‐Si:H‐based top cell and an HIT‐type bottom cell with the a‐Si:H‐based n/p junction developed as a TRJ in between. The development of a‐Si:H‐based n/p junction as a TRJ leads to an improved a‐Si:H/HIT‐type tandem cell with a better open circuit voltage (V_oc), fill factor (FF), and efficiency. The improvements in the cell performance was attributed to the wider band‐tail states in the a‐Si:H(n) layer that helps to an enhanced tunneling and recombination process in the TRJ. The best photovoltage parameters of the tandem cell were found to be V_oc = 1430 mV, short circuit current density = 10.51 mA/cm², FF = 0.65, and efficiency = 9.75%. Copyright © 2015 John Wiley & Sons, Ltd.     

High efficiency low temperature grown Cu(In,Ga)Se2 thin film solar cells on flexible substrates using NaF precursor layers

We report a total‐area efficiency of 15.9% for flexible Cu(In,Ga)Se₂ thin film solar cells on polyimide foil (cell area 0.95 cm²). The absorber layer was grown by a multi‐stage deposition process at a maximum nominal process temperature of 420°C. The Na was added via evaporation of a NaF layer prior to the absorber deposition leading to an enhanced V_oc and FF. Growth conditions and device characterization are described. Copyright © 2011 John Wiley & Sons, Ltd.     

Improvement of hydrogenated amorphous silicon germanium thin film solar cells by different p-type contact layer

In this study, we report an appreciably increased efficiency from 6% up to 9.1% of hydrogenated amorphous silicon germanium (a-SiGe:H) thin film solar cells by using a combination of different p-doped window layers, such as boron doped hydrogenated amorphous silicon (p-a-Si:H), amorphous silicon oxide (p-a-SiO_x:H), microcrystalline silicon (p-µc-Si:H), and microcrystalline silicon oxide (p-µc-SiO_x:H). Optoelectronic properties and the role of these p-layers in the enhancement of a-SiGe:H cell efficiency were also examined and discussed. An improvement of 1.62 mA/cm² in the short-circuit current density (J_sc) is attributed to the higher band gap of p-type silicon oxide layers. In addition, an increase in open-circuit voltage (V_oc) by 150 mV and fill factor (FF) by 6.93% is ascribed to significantly improved front TCO/p-layer interface contact.     

Impact of silicon quantum dot super lattice and quantum well structure as intermediate layer on p‐i‐n silicon solar cells

The photovoltaic effect of the silicon (Si)/silicon carbide (SiC) quantum dot super lattice (QDSL) and multi‐quantum well (QW) strucutres is presented based on numerical simulation and experimental studies. The QDSL and QW structures act as an intermediate layer in a p‐i‐n Si solar cell. The QDSL consists of a stack of four 4‐nm Si nano disks and 2‐nm SiC barrier layers embedded in a SiC matrix fabricated with a top‐down etching process. The Si nano disks were observed with bright field‐scanning transmission electron microscopy. The simulation results based on the 3D finite element method confirmed that the quantum effect on the band structure for the QDSL and QW structures was different and had different effects on solar cell operation. The effect of vertical wave‐function coupling to form a miniband in the QDSL was observed based on the solar‐cell performance, showing a dramatic photovoltaic response in generating a high photocurrent density J_sc of 29.24 mA/cm², open circuit voltage V_oc of 0.51 V, fill factor FF of 0.74, and efficiency η of 11.07% with respect to a i‐QW solar cell with J_sc of 25.27 mA/cm², V_oc of 0.49 V, FF of 0.69, and η of 8.61% and an i‐Si solar cell with J_sc of 27.63 mA/cm², V_oc of 0.55 V, FF of 0.61, and η of 10.00%. A wide range of photo‐carrier transports by the QD arrays in the QDSL solar cell is possible in the internal quantum efficiency spectra with respect to the internal quantum efficiency of the i‐QW solar cell. Copyright © 2015 John Wiley & Sons, Ltd.     

Laser‐fired contact optimization in c‐Si solar cells

In this work we study the optimization of laser‐fired contact (LFC) processing parameters, namely laser power and number of pulses, based on the electrical resistance measurement of an aluminum single LFC point. LFC process has been made through four passivation layers that are typically used in c‐Si and mc‐Si solar cell fabrication: thermally grown silicon oxide (SiO₂), deposited phosphorus‐doped amorphous silicon carbide (a‐SiC_x/H(n)), aluminum oxide (Al₂O₃) and silicon nitride (SiN_x/H) films. Values for the LFC resistance normalized by the laser spot area in the range of 0.65–3 mΩ cm² have been obtained. Copyright © 2011 John Wiley & Sons, Ltd.     

Efficient Polymer Solar Cells with a High Open Circuit Voltage of 1 Volt

A series of polymers containing benzo[1,2‐b:4,5‐b′]dithiophene and N‐alkylthieno[3,4‐c]pyrrole‐4,6‐dione are designed. By incorporating different alkylthienyl side chains, the fill factor (FF) and open circuit voltage (V_oc) of the copolymers are further improved. The experimental results and theoretical calculations show that the size and topology of the side chains can influence the polymer solubility, energy levels, and intermolecular packing by altering the molecular coplanarity. As a result of improved morphology and fine‐tuned energy levels, an increased FF and a high V_oc of 1.00 V are achieved, as well as a power conversion efficiency of 6.17%, which is the highest efficiency ever reported for polymer solar cells with a V_oc over 1 V.     

Structural analyses of seeded thin film microcrystalline silicon solar cell

This contribution investigates the effect of seeding the growth of thin film microcrystalline silicon (µc‐Si : H) deposited by radio frequency plasma‐enhanced chemical vapor deposition on the material properties of µc‐Si : H film and the device performance of p‐i‐n and n‐i‐p µc‐Si : H solar cells. By means of Raman measurement, x‐ray diffraction (XRD) and transmission electron microscopy (TEM), we investigate the structure of seeded µc‐Si : H. In particular, the effect of seed layers on the crystallinity development is investigated. Measurements of the depth profile of the crystalline mass fraction using Raman spectroscopy show that seed layers lead to a more rapid and uniform crystallinity development in growth direction. The amorphous incubation layer is suppressed and crystallization begins directly from onset of film growth without evolving through the intermediate growth phases. From TEM analyses, we observe that crystal sizes are not affected by seed layers. Horizontal cracks are however observed to dominate the early growth of µc‐Si : H in p‐i‐n solar cell and this is reduced upon seeding. For the n‐i‐p cells, these cracks are not affected by seeding. XRD results also indicate that the use of seed layers does not affect the crystal sizes but affects the direction of preferential orientation. Solar cell external parameters show that seeding of p‐i‐n solar cells leads mainly to increase in short‐circuit current density, J_sc with a slight drop in open‐circuit voltage, V_oc. For the n‐i‐p cells, a reverse effect is observed. In this case, the V_oc increases and the J_sc decreases. Copyright © 2012 John Wiley & Sons, Ltd.     

Achievement of 17.9% efficiency in 30 × 30 cm2 Cu(In,Ga)(Se,S)2 solar cell sub‐module by sulfurization after selenization with Cd‐free buffer

We have achieved 17.9% efficiency in a 30 × 30 cm² Cu(In,Ga)(Se,S)₂ solar cell sub‐module prepared by selenization and sulfurization processes with a Cd‐free buffer. The development of an absorber layer, transparent conducting oxide window layer, and module design was the key focus. This permitted 1.8% higher efficiency than our last experimental result. The quantity and the injection time of the sodium were controlled, resulting in higher open circuit voltage (V_oc) and short circuit current (J_sc). In order to increase J_sc, we changed the thickness of the window layer. Boron‐doped zinc oxide was optimized for higher transmittance without reducing the fill factor. The uniformity of each layer was improved, and patterns were optimized for each module. Therefore, V_oc, J_sc, and FF could be theoretically improved on the reported results of, respectively, 20 mV, 2 mA/cm², and 1.4%. The module's efficiency was measured at the Korea Test Laboratory to compare with the data obtained in‐house. Various analyses were performed, including secondary ion mass spectroscopy, photoluminescence, quantum efficiency, solar simulator, and UV–vis spectrometry, to measure the cell's depth profile, carrier lifetime, external quantum efficiency, module efficiency, and transmittance, respectively. Copyright © 2015 John Wiley & Sons, Ltd.