shockley queisser limit bandgap

Although efficiencies exceeding 15% have been frequently reported, it is widely acknowledged that the moderate bandgap of 1.55eV offers enormous potential to further enhance the device efficiency by using multi-junction configurations39,40. 6:7730 doi: 10.1038/ncomms8730 (2015). . These cells would combine some of the advantages of the multi-junction cell with the simplicity of existing silicon designs. and V.V.R. A factor fc gives the ratio of recombination that produces radiation to total recombination, so the rate of recombination per unit area when V=0 is 2tcQc/fc and thus depends on Qc, the flux of blackbody photons above the band-gap energy. A series-connected organic tandem solar cell absorbing photons in the NIR range is stacked in a four-terminal configuration behind a semitransparent perovskite cell. It should be no surprise that there has been a considerable amount of research into ways to capture the energy of the carriers before they can lose it in the crystal structure. Dennler, G. et al. Google Scholar. Dyes, rare-earth phosphors and quantum dots are actively investigated for fluorescent downshifting. The Shockley-Queisser-Limit is a limit of light-based devices. 8, 689692 (2008) . Sub-1.4eV bandgap inorganic perovskite solar cells with long-term Series/parallel triple-junction cells with organic, as well as perovskite-based subcells may become a key technology to further advance the efficiency roadmap of the existing photovoltaic technologies. 26, 56705677 (2014) . Accordingly, the SP interconnection provides a more feasible approach to reach its theoretical efficiency limit. Our recent work demonstrated that a thin layer of ZnO nanoparticles can effectively conduct electrons to the AgNW electrode and, more importantly, enable the deposition of the AgNW electrode by doctor blading from water-based solution.16,17 However, both ZnO and AgNW layers are obviously not compact enough to protect the underlying subcells from solvent infiltration during the top subcell deposition. This is why the efficiency falls if the cell heats up. Pettersson, L. A. For our SP triple-junction organic solar cells, with the exception of bottom ITO-coated glass substrate and top evaporated MoOX/Ag electrode, all the layers were sequentially deposited using a doctor blade in ambient atmosphere. Detailed description of the device fabrication procedure is presented in the Methods section and schematically illustrated in Supplementary Fig. A wide variety of optical systems can be used to concentrate sunlight, including ordinary lenses and curved mirrors, fresnel lenses, arrays of small flat mirrors, and luminescent solar concentrators. March 28, 2019 In science, the Shockley-Queisser limit, refers to the maximum theoretical efficiency of a conventional solar cell using a single p-n junction to collect power from the cell. 137, 13141321 (2015) . fabricated and characterized the organic solar cells. Adv. Efficient organic solar cells with solution-processed silver nanowire electrodes. This is a very small effect, but Shockley and Queisser assume that the total rate of recombination (see below) when the voltage across the cell is zero (short circuit or no light) is proportional to the blackbody radiation Qc. [28], Another possibility for increased efficiency is to convert the frequency of light down towards the bandgap energy with a fluorescent material. The generalized Shockley-Queisser limit for nanostructured solar cells Print. In the following, we start with the demonstration of the integrated SP triple-junction cells for solution-processed organic solar cells. Sci. They used blackbody radiation of 6000K for sunlight, and found that the optimum band gap would then have an energy of 2.2 kTs. In real parallel-connected solar cells, however, the VOC of the tandem cells can be close either to the subcell with high VOC or to the subcell with low VOC depending on the series resistance of the subcells37. Phys. Nat. In cases where outright performance is the only consideration, these cells have become common; they are widely used in satellite applications for instance, where the power-to-weight ratio overwhelms practically every other consideration. Energy Mater. is the number of photons above the band-gap energy falling on the cell per unit area, and ts is the fraction of these that generate an electron-hole pair. Adv. Effects of shadowing on to photovoltaic module performance. These observations provide sufficient evidence that there are no resistive losses for the intermediate AgNW electrode in terms of collecting charge carriers. Other recombination processes may also exist (see "Other considerations" below), but this one is absolutely required. The purpose of this study is to determine the optimum location for intermediate band in the middle of band gap of an ideal solar cell for maximum performance. Mater. The SP and PS configurations are distinguished by the stacking sequence of the two interconnections (parallel and series) depending on which interconnection the light passes through first. D. Appl. In our parallel-connected constituent subcells, the two top subcells showed series resistance of 1cm2 which is almost eight times lower than those of bottom DPPDPP subcells (Table 2). ) Opt. ITO-free and fully solution-processed semitransparent organic solar cells with high fill factors. 7, 399407 (2014) . One way to reduce this waste is to use photon upconversion, i.e. Energy Mater. Green, M. A., Ho-Baillie, A. conceived the device concept. Devos, A. 300 K . ACS Nano 4, 37433752 (2010) . PDF Power conversion efficiency exceeding the Shockley-Queisser limit in a Considering the spectrum losses alone, a solar cell has a peak theoretical efficiency of 48% (or 44% according to Shockley and Queisser their "ultimate efficiency factor"). The scale bar, 400nm. Compared with the reference DPPDPP tandem cell, the slightly reduced VOC of 0.020.03V can be attributed to shadow effect36, because a mask with an aperture smaller than either electrode was adopted to define the active area during the JV measurement. Another possibility is to use two-photon absorption, but this can only work at extremely high light concentration.[19]. Sci. Due to the lack of the back reflective electrode, the semitransparent tandem device shows a relatively low short circuit current (JSC) of 5.16mAcm2. Shockley-Queisser limit - Infogalactic: the planetary knowledge core Adv. This allows for higher theoretical efficiencies when coupled to a low bandgap semiconductor[26] and quantum efficiencies exceeding 100% have been reported. Science 334, 15301533 (2011) . Due to the well-matched VOC between the perovskite cell and the series-connected tandem cell, the photocurrent delivered by the organic tandem cell, up to 2mAcm2, directly contributes to the performance enhancement of the perovskite cell. Prog. This first calculation used the 6000K black-body spectrum as an approximation to the solar spectrum. Q 86, 487496 (1999) . The maximum value of f without light concentration (with reflectors for example) is just f/2, or 1.09105, according to the authors. There is an optimal load resistance that will draw the most power from the solar cell at a given illumination level. Sista, S., Hong, Z. R., Park, M. H., Xu, Z. The product of the short-circuit current Ish and the open-circuit voltage Voc Shockley and Queisser call the "nominal power". For a converter with a bandgap of 0.92 eV, efficiency is limited to 54% with a single-junction cell, and 85% for concentrated light shining on ideal components with no optical losses and only radiative recombination.[32]. (At that value, 22% of the blackbody radiation energy would be below the band gap.) F.G. and N.L. [13] Since imaginary dielectric functions is, even though low, non-zero below the optical gap, there is absorption of light below the optical gap. The hybrid platform offers sunlight-to-electricity conversion efficiency exceeding that imposed by the S-Q limit on the corresponding PV cells across a broad range of bandgap energies, under low optical concentration (1-300 suns), operating temperatures in the range 900-1700 K, and in simple flat panel designs. The first intermediate layers, ZnO and N-PEDOT:PSS, were sequentially bladed at 50C and annealed at 80C for 5min in air and the obtained layer thickness for both layers is 35nm. When an electron is ejected through photoexcitation, the atom it was formerly bound to is left with a net positive charge. The parallel-connection between the semitransparent perovskite and series-connected DPPDPP subcells was realized by external coupling using Ag paste. 5c,d, if we mathematically add the JV curves of the DPPDPP subcells with the top PCDTBT or OPV12 subcell at each voltage bias (Vbias), a perfect fitting of the constructed JV curve with the experimentally measured JV curve of the triple-junction device is observed, which is consistent with Kirchhoff's law. J. Appl. Phys. Recombination places an upper limit on the rate of production; past a certain rate there are so many holes in motion that new electrons will never make it to the p-n junction. to find the impedance matching factor. On contrary, the fact that the AgNWs partially sink into N-PEDOT can reduce the roughness of the NW networks, which is beneficial for building the upper few layers and further reduces the possibility of shunts in the top subcell. Phys. Energy Environ. Guo, F. et al. N.p. Li, W. W., Furlan, A., Hendriks, K. H., Wienk, M. M. & Janssen, R. A. J. Sci. Herein, we chose ZnO and neutral PEDOT:PSS (N-PEDOT) as the N- and P-type charge extraction materials, respectively, because the work functions of the two materials match well with the energy levels of the donor DPP and acceptor PC60BM20,23. The record efficiencies of several types of solar. https://doi.org/10.1038/ncomms8730. Li, N. et al. Solution processed polymer tandem solar cell using efficient small and wide bandgap polymer:fullerene blends. The benefit of this series/parallel (SP) multi-junction design is based on the fact thatfirst, the absorber layer of the front semitransparent hero cell can be made arbitrarily thick (as there is no requirement for current matching), so that this subcell can achieve almost the same efficiency as the opaque single-junction reference. (a) Equivalent electronic circuit of the series/series (SS) triple-junction organic solar cells. In the meantime, to ensure continued support, we are displaying the site without styles 0 the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in [23] One system under investigation for this is quantum dots. Quantum dots have been extensively investigated for this effect, and they have been shown to work for solar-relevant wavelengths in prototype solar cells. performed the optical simulations. One of the main loss mechanisms is due to the loss of excess carrier energy above the bandgap. If the band gap is large, not as many photons create pairs, whereas if the band gap is small, the electron-hole pairs do not contain as much energy. In particular, to exceed the ShockleyQueisser limit, it is necessary for the fluorescent material to convert a single high-energy photon into several lower-energy ones (quantum efficiency > 1). Chem. All the materials were used as received without further purification. To push the performances of these solar technologies beyond the ShockleyQueisser limit, several approaches have been proposed, for instance, up-conversion3, multi-junction configuration4,5,6, multiple exciton generation7,8 and concentrator cells, and so on. Environmentally printing efficient organic tandem solar cells with high fill factors: a guideline towards 20% power conversion efficiency. We chose silver nanowires (AgNWs) as the intermediate electrode for our triple-junction devices because of their high transparency and low sheet resistance as well as the facile solution processability26,27,28,29,30. For example, a planar thermal upconverting platform can have a front surface that absorbs low-energy photons incident within a narrow angular range, and a back surface that efficiently emits only high-energy photons. J. The device structure of the single and tandem reference cells are: Glass/ITO/PEDOT:PSS/DPP:PC60BM/Ca/Ag and Glass/ITO/PEDOT:PSS/DPP:PC60BM/ZnO/N-PEDOT/DPP:PC60BM/Ca/Ag. Energy Environ. Liftout sample for TEM was prepared with FEI Helios Nanolab 660 DualBeam FIB, from the area-of-interest containing all layers of the solar cell. ITO-coated glass substrates (2.5 2.5)cm2 with a sheet resistance of 15sq1 were purchased from Weidner Glas and patterned with laser before use. To achieve a reliable contact between the middle AgNW electrode and probes of the measurement set-ups (JV and EQE measurements), silver paste or evaporated silver was applied to the exposed AgNWs (Supplementary Fig. In crystalline silicon, even if there are no crystalline defects, there is still Auger recombination, which occurs much more often than radiative recombination. The ShockleyQueisser limit only applies to conventional solar cells with a single p-n junction; solar cells with multiple layers can (and do) outperform this limit, and so can solar thermal and certain other solar energy systems. The STEM energy dispersive X-ray spectrometry (EDS) elemental maps (Ag, Zn and S) of the cross-section shown in Fig. A detailed limit calculation for these cells with infinite bands suggests a maximum efficiency of 77.2%[18] To date, no commercial cell using this technique has been produced. Previous search for low-bandgap (1.2 to 1.4 eV) halide perovskites has resulted in several candidates, but all are hybrid organic-inorganic compositions, raising potential concern regarding . The author has contributed to research in topic(s): Solar cell & Solar cell research. Electron. Sign up for the Nature Briefing newsletter what matters in science, free to your inbox daily. Thus the rate of recombination, in this model, is proportional to exp(V/Vc) times the blackbody radiation above the band-gap energy: (This is actually an approximation, correct so long as the cell is thick enough to act as a black body, to the more accurate expression[7][8], The difference in maximum theoretical efficiency however is negligibly small, except for tiny bandgaps below 200meV. The optical simulations reveal that the as-proposed SP triple-junction organic solar cells hold the potential to achieve high efficiencies close to those of the fully series-connected counterparts, but allowing a much wider choice of material combinations. V Cite this article. Soc. V.R.R. Solar Cell Shockley-Queisser Limit Calculator - GitHub Afterwards, ZnO and N-PEDOT were again deposited onto the second DPP:PC60BM layer using the same coating parameters as for the first deposition. Trupke, T., Green, M. A. In silicon the conduction band is about 1.1 eV away from the valence band, this corresponds to infrared light with a wavelength of about 1.1microns. These photons will pass through the solar cell without being absorbed by the device. The JSC values of the top subcells were verified with EQE measurement (Supplementary Fig. Detailed assumptions and calculation procedure are presented in the Supplementary Note 1. J. Phys. "Detailed Balance Limit of Efficiency of p-n Junction Solar Cells", "Photovoltaic Cells (Solar Cells), How They Work", "Photon Collection Efficiency of Fluorescent Solar Collectors", "Microsystems Enabled Photovoltaics, Sandia National Laboratories", "Hot Carrier Solar Cell: Implementation of the Ultimate Photovoltaic Converter", "Peak External Photocurrent Quantum Efficiency Exceeding 100% via MEG in a Quantum Dot Solar Cell", "External Quantum Efficiency Above 100% in a Singlet-Exciton-FissionBased Organic Photovoltaic Cell", "Sunovia, EPIR Demonstrate Optical Down-Conversion For Solar Cells", "Theoretical limits of thermophotovoltaic solar energy conversion", Reproduction of the ShockleyQueisser calculation (PDF), https://en.wikipedia.org/w/index.php?title=ShockleyQueisser_limit&oldid=1137475907, Articles with dead external links from January 2018, Articles with permanently dead external links, Creative Commons Attribution-ShareAlike License 3.0, One electronhole pair excited per incoming photon, Thermal relaxation of the electronhole pair energy in excess of the band gap, Illumination with non-concentrated sunlight. A generic concept to overcome bandgap limitations for designing highly efficient multi-junction photovoltaic cells. 4, 36233630 (2013) . 13068. . Second, the VOC of the back cell, which is consisting of a series-connection of deep NIR absorbers, can be custom fabricated by stacking an arbitrary sequence of semiconductors with different bandgaps in series. The semitransparent perovskite (mixed halide CH3NH3PbI3xClx) solar cells with a device structure of ITO/PEDOT:PSS/Perovskite/PC60BM/ZnO/AgNWs (Supplementary Fig. [27], Also in materials where the (excited) electrons interact strongly with the remaining electrons such as Mott insulators multiple excitons can be generated. 3, 15971605 (2013) . Indeed, independent measurement of the AgNW electrode employed in the current study shows an average visible transmittance of 90% (Fig. The power conversion efficiency (PCE) of a single-junction photovoltaic cell is fundamentally constrained by the ShockleyQueisser limit1. Thus, the novel triple-junction concept demonstrated in this work provides an easy but elegant way to manufacture highly efficient photovoltaic cells, not only for conventional but also for the emerging solar technologies. 2, the absorption profiles of the two active layers are complementary with that of DPP:PC60BM, suggesting they are appropriate material combinations for manufacturing multi-junction devices. 92, 41174122 (2002) . Designing Heterovalent Substitution with Antioxidant Attribute for High Energy Mater. After all the solution-processed layers were completed, Q-tips dipped with toluene were used to clean the edges of the substrate to expose the bottom ITO and middle AgNW contacts. For a zoc of 32.4, we find zm equal to 29.0. In practice, the choice of whether or not to use light concentration is based primarily on other factors besides the small change in solar cell efficiency. AM1.5 Spectrum There is a trade-off in the selection of a bandgap. On the cleaned substrates, PEDOT:PSS (Clevious P VP Al 4083, 1:3 vol.% diluted in isopropanol) was firstly bladed and annealed at 140C for 5min to obtain a layer thickness of 40nm. Recently, indoor photovoltaics have gained research attention due to their potential applications in the Internet of Things (IoT) sector and most of the devices in moder (b) A cross-sectional TEM image of the as-prepared triple-junction solar cell. K.F. Soc. 2b. This relies on a practical IR cell being available, but the theoretical conversion efficiency can be calculated. Adebanjo, O. et al. One can then use the formula. The calculation of the fundamental efficiency limits of these multijunction cells works in a fashion similar to those for single-junction cells, with the caveat that some of the light will be converted to other frequencies and re-emitted within the structure. . Tang, J. et al. It is worth mentioning that we have employed a simple modified doctor blading technique to coat the AgNW electrode16, which enables the deposition of the NW film in a stripe and thereby eliminates any subsequent patterning steps. Light absorbers DPP, OPV12 and PCDTBT were purchased from BASF, Polyera and 1-Materials, respectively. The general applicability of the proposed triple-junction configurations has also been verified in organic-inorganic hybrid triple-junction devices. A blackbody at 6000K puts out 7348W per square centimetre, so a value for u of 44% and a value of 5.731018 photons per joule (corresponding to a band gap of 1.09V, the value used by Shockley and Queisser) gives Qs equal to 1.851022 photons per second per square centimetre. Module datasheets normally list this temperature dependency as TNOCT (NOCT - Nominal Operating Cell Temperature). The origin of high efficiency in low-temperature solution-processable bilayer organometal halide hybrid solar cells. The calculated bandgap required for the semiconductor to achieve the Shockley-Queisser limit is 1.34 eV , which is higher than the average band gap of perovskite materials. Nature Communications (Nat Commun) CAS (a) Device architecture of inverted solar cells with AgNW bottom electrode. High fill factors up to 68% without resistive losses are achieved for both organic and hybrid triple-junction devices. In other words, photons of red, yellow and blue light and some near-infrared will contribute to power production, whereas radio waves, microwaves, and most infrared photons will not. This rate of recombination plays a negative role in the efficiency. However, one distinct drawback of the series-connected configuration is the stringent current-matching criterion, which requires careful bandgap engineering in combination with an excellent control of the thicknesses of the respective subcells. ), The rate of generation of electron-hole pairs due to sunlight is. Absorption of a photon creates an electron-hole pair, which could potentially contribute to the current. Interface 6, 1825118257 (2014) . Adv. The semitransparent perovskite device shows a JSC=16.28mAcm2, VOC=0.94V and FF=65.6%, yielding a PCE of 10.04%. Figure 5c,d show the typical JV curves of the constructed triple-junction solar cells, DPPDPP/PCDTBT and DPPDPP/OPV12, along with the constituent subcells, respectively. The calculations assume that the only recombination is radiative. 22, E77E80 (2010) . They are very expensive to produce, using techniques similar to microprocessor construction but with "chip" sizes on the scale of several centimeters. The Schockley-Queisser (SQ) limit is a famous limit on the maximal possible efficiency of solar cells, limited only by fundamental physics. We would like to thank Cambrios Technology Corporation, Dr Mathieu Turbiez from BASF and Dr Norman Lchinger from Nanograde for the supply of AgNWs, DPP and ZnO dispersion, respectively. Q To deposit the intermediate electrode, 80-nm-thick AgNWs was bladed onto N-PEDOT at 45C and the resulting NW film showed a sheet resistance of 8sq1. Chem. Efficient tandem polymer solar cells fabricated by all-solution processing. C.J.B., F.G. and N.L. It is not actually possible to get this amount of power out of the cell, but we can get close (see "Impedance matching" below). Together with the high FF of 64.5% and VOC of 0.95V, the hybrid triple-junction device shows a PCE value of 11.34%, corresponding to a PCE enhancement by 12.5%. Shockley-Queisser Limit - PlasmaSolaris Thus the spectrum losses represent the vast majority of lost power. For organic solar cells, we followed the model proposed by Dennler et al.14,15 to calculate the efficiency potential for the four types of triple-junction architectures as a function of the bandgaps of three absorbers. (This is actually debatable if a reflective surface is used on the shady side.) The sunlight intensity is a parameter in the ShockleyQueisser calculation, and with more concentration, the theoretical efficiency limit increases somewhat. As the temperature of the cell increases, the outgoing radiation and heat loss through conduction and convection also increase, until an equilibrium is reached. The record efficiencies of few solar technologies, such as single-crystal silicon, CuInGaSe2, CdTe and GaAs solar cells are constantly shrinking the gap to their fundamental efficiency limits2. Adv. Am. Abstract. The Shockley-Queisser limit can be exceeded by tandem solar cells, concentrating sunlight onto the cell, and other methods. [12] According to Shockley-Quiesser limit, solar cell efficiency of semiconductors depend on the band gap of the material. PDF The Shockley-Queisser limit Note that the strongest top band (indicated by arrow) in the sulphur map belongs to molybdenum because of overlapping of S-K (2.307keV) and Mo-L (2.293keV) lines. C.O.R.Q., C.B. Design rules for donors in bulk-heterojunction tandem solar cells-towards 15% energy-conversion efficiency. 4, 1446 (2013) . He . They used blackbody radiation of 6000K for sunlight, and found that the optimum band gap would then have an energy of 2.2kTs. Including the effects of recombination and the I versus V curve, the efficiency is described by the following equation: where u, v, and m are respectively the ultimate efficiency factor, the ratio of open-circuit voltage Vop to band-gap voltage Vg, and the impedance matching factor (all discussed above), and Vc is the thermal voltage, and Vs is the voltage equivalent of the temperature of the Sun. 2.7 Beyond the Shockley Queisser Limit 20. 2c, the as-prepared opaque tandem device with evaporated Ca/Ag top electrode (15nm/100nm) shows a fill factor (FF) of 64.3% along with a VOC of 1.1V being the sum of two single-junction reference cells (Table 1). Solution-processed parallel tandem polymer solar cells using silver nanowires as intermediate electrode. For a zoc of 32.4, this comes to 86.5%. In the most common design, a high-bandgap solar cell sits on top, absorbing high-energy, shorter-wavelength light, and transmitting the rest. Use the Previous and Next buttons to navigate the slides or the slide controller buttons at the end to navigate through each slide. The light intensity at each wavelength was calibrated with a standard single-crystal Si solar cell. = c Science 317, 222225 (2007) . Note that in these two simulations the top PCDTBT:PC70BM layer thickness is fixed to 80nm, corresponding to the optimized thickness in their single-junction state. Materials with higher electron (or hole) mobility can improve on silicon's performance; gallium arsenide (GaAs) cells gain about 5% in real-world examples due to this effect alone. : . The V loss t otal of OSCs can be expressed in terms of E 1, E 2, and E 3 in V loss total = (E g PV /q V oc SQ) + (V oc SQ V oc Rad) + (V oc Rad V oc PV) = E 1 + E 2 + E 3, where q, E g PV, V oc SQ, V oc rad, and V oc PV are the elementary charge, photovoltaic band gap, maximum voltage in the Shockley-Queisser (SQ) limit . Photonics 8, 506514 (2014) . In addition, 23.14%-efficient all-perovskite tandem solar cells are further obtained by pairing this PSC with a wide-bandgap (1.74 eV) top cell. TEM was performed on the FEI TITAN3 Themis 60300 double aberration-corrected microscope at the Center for Nanoanalysis and Electron Microscopy (CENEM), the University of Erlangen, equipped with the super-X energy dispersive spectrometer. Kojima, A., Teshima, K., Shirai, Y. J. 5, 91739179 (2012) . Mater. By changing the location of the intermediate band, output current and therefore performance can be changed. Similar simulation results for the triple-junction DPPDPP/OPV12 devices are presented in Supplementary Fig. Centurioni, E. Generalized matrix method for calculation of internal light energy flux in mixed coherent and incoherent multilayers. [20] The upconversion efficiency can be improved by controlling the optical density of states of the absorber[21] and also by tuning the angularly-selective emission characteristics. Chen, C. C. et al. This process reduces the efficiency of the cell. The final thickness of the liftout sample was kept <100nm, to enable high quality conventional transmission electron microscopy (CTEM) imaging at an acceleration voltage of 200kV. The multi-junction concept is the most relevant approach to overcome the Shockley-Queisser limit for single-junction photovoltaic cells. In addition, as indicated in Supplementary Fig. The result is a region at the interface, the p-n junction, where charge carriers are depleted on each side of the interface. Correspondence to 9, 617624 (2008) . Luque, A., Marti, A. Commun. Since someone asked me: "I release this document and code to the public domain." Pronunciation of "Queisser": Hans-Joachim Queisser was German, so a German-speaker helped me guess how the name is pronounced. 2c) exhibits a VOC of 1.10V, which is identical to the reference tandem cell, suggesting the effective incorporation of AgNWs as the top electrode. 6, 6391 (2015) . [24][25], Another, more straightforward way to utilise multiple exciton generation is a process called singlet fission (or singlet exciton fission) by which a singlet exciton is converted into two triplet excitons of lower energy. c However, the parallel-connection is more difficult to adapt and optimize for the high-performance semiconductors with non-tunable bandgaps, such as single-crystal silicon or CdTe. JV curves of all the devices were recorded using a source measurement unit from BoTest.