Modelling Of Perovskite Solar Cells - QUT
Modelling of Perovskite Solar CellsRONGSHENG WEIMaster DegreeSubmitted in fulfilment of the requirement for the degree of Master ofEngineering (Research)FINAL THESISSCHOOL OF CHEMISTRY, PHYSICS AND MECHANICALENGINEERINGSCIENCE AND ENGINEERING FACULTYQueensland University of Technology2018
Queensland University of TechnologyCONTENTSSTATEMENT OF ORIGINAL AUTHORSHIP . 3ACKNOWLEDGEMENT . 4ABSTRACT . 5THE SUPERVISORS AND THEIR CREDENTIALS . 7CHAPTER 1. INTRODUCTION . 81.1 Energy Issues . 81.2 Solar Cells. 101.2.1 Working Mechanism in Solar Cells . 101.2.2 Main Parameters in Solar Cells . 121.3 Perovskite Solar Cells . 131.3.1 Perovskite Materials . 151.3.2 Development of Perovskite Solar Cells . 171.4 SCAPS-1D Based Numerical Simulation . 181.4.1 Basic Semiconductor Physics in SCAPS-‐1D. 201.4.2 Grading Models in SCAPS-‐1D . 231.4.3 Operation Theory . 241.4.4 Strengths and Limitations . 251.5 Research Objective and Outline . 26CHAPTER 2. NUMERICAL MODEL FOR PSCs .282.1 Introduction . 282.2 Physics Model in PSCs . 302.2.1 Basic Equations . 302.2.2 Generation and Recombination Mechanism . 322.3 Numerical Simulation Method . 342.3.1 Discretization of Equations . 342.3.2 Linearization of Equations . 362.4 Results and Discussion . 392.4.1 The Effect of Effective Density of State . 392.4.2 The Effect of Relative Dielectric Permittivity . 431
Queensland University of Technology2.4.3 The Effect of Band Gap Energy . 462.5 Conclusion . 49CHAPTER 3. SCAPS SIMULATION FOR HTM LAYER IN PSCs .503.1 Introduction . 503.2 Device Model . 523.3 Results and Discussion . 563.3.1 The Influence of HTM Layer Characteristics . 563.3.2 Comparison for Different Hole Transporting Materials . 593.4 Conclusion . 62CHAPTER 4. SUMMARY AND FUTURE WORKS .634.1 Summary . 634.2 Future Works. 63REFERENCES .65APPENDIX .722
Queensland University of TechnologySTATEMENT OF ORIGINAL AUTHORSHIPThe work contained in this report has not been previously submitted to meet requirements foran award at this or any other higher education institution. To the best of my knowledge andbelief, the report contains no material previously published or written by another person exceptwhere due reference is made.Signature:QUT Verified SignatureDate:3
Queensland University of TechnologyACKNOWLEDGEMENTFirst of all, I would like to thank my supervisor, Associate Professor Hongxia Wang. She isvery professional, and she has given me a considerable amount of help during my study at QUT.I really appreciate her sharing her knowledge of perovskite solar cells and discussing questionsabout physical models with me. She also gave me many valuable suggestions regarding myproject and thesis. I also would like to thank Professor Aijun Du and Fawang Liu for givingme the guidance regarding my thesis and numerical modelling. As well, I would like to thankmy research group members, including Shengli Zhang, Teng Wang, Nima and Disheng Yao.My sincere thanks also go to Libo Feng, who is a member of another group. All of them gaveme lots of assistance during my project and I have really appreciated their generosity. Iacknowledge the services of professional editor, Diane Kolomeitz, who provided copyeditingand proofreading services, according to the guidelines laid out in the university-endorsednational ‘Guidelines for editing research theses’. Finally, I want to thank my family membersfor their ongoing support, both financially and emotionally. Without them, I would not haveachieved what I have got today.4
Queensland University of TechnologyABSTRACTPerovskite solar cells have become a hot topic in the solar energy device area. With 10 yearsof development, the energy conversion efficiency has seen a great improvement from 2.2% tomore than 22%, and it still has great potential for further enhancement. Numerical simulationis a crucial technique in deeply understanding the operational mechanisms of solar cells and inpredicting the maximum value of a solar cell with controlled design. This technique can alsogive guidance on the structure optimisation for different devices. In this project, two main areasof research have been discussed. The first part of this thesis illustrates a numerical model ofperovskite solar cells (PSCs) by using the Matlab program. It also introduces a specificcomputation process for this model. This model is used to study semiconductor physics in PSCsand investigate the effect of three parameters on device performance: density of state, relativedielectric permittivity and band gap energy. The simulation results reveal that a large value ofeffective density state can decrease both short-circuit current (Isc) and open-circuit voltage (Voc)in particular on Voc. A large value of relative dielectric permittivity can cause a large Voc andIsc, but the effect is not significant. Larger band gap energy is beneficial for the Voc and Iscwithout considering reduction of light absorption. The second part shows a model of aperovskite solar cell with the structure of glass/ FTO/ TiO2/ CH3NH3PbI3/ HTM/ Au by usingSCAPS-1D software. The influence of hole transport material layer characteristics, includinghole mobility and band gap offset, on the performance of PSCs are investigated by using thismodel with Spiro-MOeTAD. Besides Spiro-OMeTAD, two-hole transport materials based oninorganic materials including CuO and Cu2O are also discussed. The simulation results showthat with the increase of hole mobility in the HTM layer, the value of PCE is enhanced. When5
Queensland University of Technologyhole mobility reaches 5e-3 cm2/Vs, PCE closes to the maximum value and the change reachesa plateau. The device can obtain high performance when the value of the valance band gapoffset is between -0.2 eV and 0.2 eV. Furthermore, the device shows a better performance byusing inorganic materials (CuO, Cu2O) as the HTM layer, than by using spiro-MOeTAD,especially to Cu2O with a PCE of 21.87%.Key Words: Perovskite solar cell, Matlab, SCAPS-1D, Modelling6
Queensland University of TechnologyTHE SUPERVISORS AND THEIR CREDENTIALSPrincipal Supervisor: Assoc. Prof. Hongxia WangHongxia Wang is an Associate Professor of Energy and Process Engineering in the Faculty ofScience and Engineering of Queensland University of Technology (QUT). She is a member ofthe Royal Australian Chemical Institute, MRACI, and a member of the Australian PhotovoltaicInstitute. Her research areas focus on energy conversion and storage devices, semiconductormaterials, and the charge transport process.Associate Supervisor: Prof. Aijun DuAijun Du is a Professor of Energy and Process Engineering in the Faculty of Science andEngineering of Queensland University of Technology (QUT). He is a member of the AustralianResearch Council Nanotechnology Network, American Nano Society and American ChemicalSociety. His research areas are related to clean energy, nanoelectronics, and environment,through the use of advanced theoretical modelling.7
Queensland University of TechnologyCHAPTER 1. INTRODUCTION1.1 Energy IssuesWith the rapid development of the economy, the demand for energy is increasing. Aninvestigation from the World Energy Resources has predicted that global population will reachto 8.1 billion in 2020, and total primary energy supply is expected to reach 17208 Mtoe in 2020[1]. Shafiee and Topal have reported that the world’s reserves of oil, gas and coal will be nearlyused up after 35 years, 37 years and 107 years respectively [2]. In addition, a growing numberof research works have shown that the issues, such as pollution and global warming, are theconsequence of burning of fossil fuels [3]. Along with the issue of depletion of fossil fuels,environmental pollution and global warming caused by burning of fossil fuels have raisedsignificant concerns as well. Thus, an urgent mission is to find an alternative source, which isclean, renewable and sustainable, to replace fossil fuels. Solar energy is an infinite, clean andflexible energy, and it can be converted into many other categories of energy for differentdemands. Compared with other renewable energy resources such as hydropower, wind energy,bioenergy, geothermal and nuclear energy, solar energy is more accessible and rich [4]. Solartechnology has developed rapidly in the past decades. It successfully overcomes the technicaldifficulties for improving efficiency of energy conversion, meanwhile, it reduces the cost thatmeets the requirements of commercialisation [5]. Fig.1.01 illustrates different energyconsumptions from 2005 to 2015; from this, it is clear that the proportion of solar energyconsumption has increased more than 40 times from 2005 to 2015. Furthermore, the cost ofelectricity generated from the solar PV and solar thermal has reduced significantly comparedwith 2010 and 2015, as shown in Fig.1.02 [6]. It is clear that solar energy as a renewable energy8
Queensland University of Technologyis promising to change the world’s energy pattern. It also has a lot of room to progress with thecontinuous improvement of technology.Fig.1.01The comparative energy consumption in 2005, 2010, and 2015 [1]Fig.1.02 The tendency of global renewable energy cost of electricity in 2010 and 2015 [1]9
Queensland University of Technology1.2 Solar CellsThe solar cell is an important energy conversion device harnessing solar energy. The first solarcell was fabricated by using single silicon crystal in Bell labs, which showed an energyconversion efficiency of 6% in 1954 [7]. The first commercial silicon solar cell was reportedin 1955, with a 2% efficiency. Because of the high cost and price, very few people actuallyused the solar cell for home application, but it gradually began to be widely used in daily lifeafter 1973 [8]. A new type of solar cell with low fabrication cost and 10% efficiency was madeat the Institute of Energy Conversion of University of Delaware in 1980; it was called thin filmsolar cell [9]. In 1982, a polysilicon solar cell was widely produced using a casting method, bythe Kyocera Corporation [10]. In 1991, Michael Gratzel and Brian O’Regan reported a newtype of solar cell called dye-sensitized solar cells (DSSCs), and further reducd the cost offabrication by 50% compared to silicon solar cells, by using solution processes in 1988 [11].Since then, research on solar cells has entered the third generation. Perovskite solar cells (PSCs)are derived from the research concept of dye-sensitized solar cells.1.2.1 Working Mechanism in Solar CellsSolar cells are made by semiconductor materials, which can generate electricity from sunlightdirectly by using a photovoltaic effect. When a solar cell is exposed to light, a portion of thephoton with the energy larger than the bandgap is absorbed by the semiconductor. Theabsorbed photons with sufficient excitation energy (E Egap) can cause the transport of electronsand holes; electrons in the conduction band and holes in the valence band move in differentdirections, as shown in Fig.1.03 [12].10
Queensland University of TechnologyFig.1.03 Excitation and charge separation [12]Fig.1.04 Working principle of solar cell [13]The carriers, which are generated around the P-N junction, reach the space charge regionwithout recombination. Due to the effect of an internal electric field, holes diffuse into the Ptype region, and electrons flow into the N-type region. As a result, there are excess holes in theP-type region and electrons, which are stored in the N-type region, have the same situation.Excess electrons and holes form an electrostatic field near the P-N junction, which has theopposite direction to the potential energy barrier. The electrostatic field can not only offsetparts of the potential energy barrier effects, but also make the P-type region have positiveelectricity and N-type region have negative electricity. As a consequence, the electromotiveforce is created between these two regions [13]. If there is a circuit loop, current can beproduced. The complete process is shown in Fig.1.04.11
Queensland University of Technology1.2.2 Main Parameters in Solar CellsThe performance parameters of a solar cell mainly refer to the output characteristics of thedevice (I-V) including short-circuit current, open-circuit voltage, fill factor and powerconversion efficiency [14], as shown in Fig.1.05.Fig.1.05 Output characteristics of the device (I-V) [14]l Open-circuit voltage: The open-circuit voltage is the maximum output voltage of solarcells. It can be obtained when the value of the output current is zero. Open-circuit voltagecan be expressed by Eq.1.1𝑉"# %& '(,𝐿𝑛[ 1],-(1.1)where, 𝑘2 is the Boltzmann constant, T is temperature, q is elementary charge, I is thelight-generated current density, I0 is the saturation current density.l Short circuit-current: Set a solar cell under a standard light source, when the output is inshort circuit state, which means the voltage value is 0, the current is the maximum outputcurrent called short-circuit current. It is given as:9:𝐼4# 𝐼 𝐼6 (𝑒 ;& 1)12(1.2)
Queensland University of Technologyl Fill factor: This is the ratio of maximum output power to the open circuit voltage and shortcircuit current. Fill factor is associated with maximum output power. A higher fill factorleads to a greater output power. The valueof fill factor depends on series resistance andvoltage. Fill factor is defined by using the equation below:𝐹𝐹 ?@ABC ,DC(1.3)Where, Pm is the maximum output power. Voc is the open-circuit voltage. J is the shortcircuit current.l Power conversion efficiency: Power conversion efficiency (PCE) is a significantparameter. It is defined as the ratio of the maximum output power to the incident lightpower, as shown in Eq.14.𝜂 ,DC GG ABC?HI(1.4)where, 𝑃KL is the incident light power. It can be easily seen from this equation that thevalue of power conversion efficiency is determined by Isc, FF, Voc and Pin.1.3 Perovskite Solar CellsIn 2012, Nature published an article of a perovskite solar cell with an efficiency over 10%.Since then, perovskite solar cells have drawn a lot of attentions due to their high performance,low cost of fabrication and great potential for commercialisation [15]. Generally, the structureof perovskite solar cells consists of five layers, which are a metal-based cathode layer, holetransporting material (HTM) layer, perovskite layer, electron transporting material (ETM)layer and anode (FTO/ITO). A typical perovskite solar cell with planar structure is shown in13
Queensland University of TechnologyFig.1.06. The perovskite layer is used as a light absorber in the device, where photon excitationoccurs. The generated electrons and holes are separated and transferred to the ETM layer andHTM layer respectively. Due to its ambipolar characteristic, perovskite has a high mobility ofboth electrons and holes. The function of the ETM layer is to extract and transfer electrons andblock holes. For the HTM layer, it is used to extract and transfer holes and block electrons. Itmeans high mobility for electrons in the ETM layer, high mobility for holes in the HTM layer,and appropriate band offsets between ETM layer/perovskite layer/HTM layer that arenecessary for high efficiency [16-20]. The main processes of charge transport in perovskitesolar cells are shown in Fig.1.07. The green arrows represent the favourable processes forenergy conversion including photon excitation, transportation of electrons from perovskitelayer to ETM layer, and transportation of holes from perovskite layer to HTM layer. The redarrows indicate the undesirable processes, which cause energy loss, in perovskite solar cellsinvolving the recombination of charge carriers, back electron flow from the ETM layer andhole flow from the HTM layer to perovskite layer [21].Fig.1.06. The configuration of perovskite solar cell with planar structure [40]. Fig.1.07Schematics showing of charge transport in perovskite solar cells [40]14
Queensland University of Technology1.3.1 Perovskite MaterialsPerovskite material is a type of material that shares similar crystal structure with calciumtitanate (CaTiO3) and can be expressed as ABX3 [22]. As shown in Fig.1.08, A is organicammonium, such as CH3- NH 3, B is metal cation, (e.g. Pb2 ), X is halide anion (e.g. Cl, Br, I.In the crystal structure, A ion is surrounded by eight three-dimensional structure of a cornersharing octahedral BX6 units [23].Fig.1.08 The Perovskite crystal structure [40]The probable crystallographic structure of a perovskite material can be predicted by analysinga tolerance factor t and an octahedral factor u. t can be expressed as Eq.1.01.𝑡 (𝑟O 𝑟P )/( 2[𝑟2 𝑟P ])(1.01)where, rA, rB and rX are the ionic radii of A, B and X respectively. The report shows that thetolerance factors of most perovskite materials lie in the range from 0.75 to 1 [24]. However, itis not enough to deduce the probable crystallographic structure of perovskite materials by only15
Queensland University of Technologyconsidering tolerance factors. Therefore, the octahedral factor u is used as an additionalindicator to predict the formation of perovskite structure. U can be described by Eq.1.02.𝑢 𝑟2 /𝑟P(1.02)Generally, the ABX3 perovskite structure can be formed under the conditions of 0.813 t 1.107 and 0.442 u 0.895 [25]. The structure map by considering t and u for ABX3perovskite materials is shown in Fig.1.09.Fig.1.09 The structure map for ABX3 perovskite materials [25]Compared with other materials, perovskite materials have their own unique characteristics suchas appropriate band gap energy (around 1.55eV), long carrier lifetime and diffusion length, andhigh extinction coefficient [26-39]. Due to these favourable characteristics, perovskitematerials are widely applied as a light absorber in solar cell device. However, they also havesome limitations including low stability under moisture and ultraviolet radiation environments,which are easily to result in degradation of performance, and the effect of toxicity problems,caused from the toxicity ion of Pb2 on both the environment and the human body during thefabrication and disposal processes [30-31].16
Queensland University of Technology1.3.2 Development of Perovskite Solar CellsThe first perovskite solar cell was reported by Miyasaka and colleagues in 2006. They usedCH3NH3PbBr3 as the material and obtained a solar cell with an efficiency of 2.2% [32]. Threeyears later in 2009, they used iodine instead of bromine, and the efficiency achieved by thesolar cell rose to 3.8% [33]. Park and co-workers furthered the increase in efficiency to 6.5%through the TiO2 surface treatment in 2011. The perovskite quantum dot (QD) sensitized solarcell has a better light absorption compared with the dye-sensitized solar cell. However, thestability of the perovskite QD-sensitized solar cell is low, because QD dissolves into electrolytesolution [34]. In order to avoid the effects from electrolytes, Park and teammates attempted touse solid state organic molecules or polymers as HTM to replace the liquid electrolytes. Theyused Spiro-MeOTAD based HTM with mesoscopic TiO2 as ETM to improve the devicestability. They achieved a solar cell with an efficiency of 9.7% in 2012 [35]. In the same year,Snaith and colleagues reported perovskite solar cells using Spiro-MeOTAD based HTM andAl2O3 as scaffold. The device presented an efficiency of 10.9%. In their report, they showedthat a better performance can be obtained by using mixed-halide (CH3NH3PbI3-xClx) due toimproved ability of charge transport. They also showed that perovskites had a bipolar chargecarrier transport of electron and hole [36]. In 2013, Seok, Grätzel and colleagues reported anefficiency of 12.3% by using the structure of nanoporous TiO2 infiltrated by mixed-halideperovskite [37]. Simultaneously, an efficiency over 15% was reported from Burschka andgroup members by using TiO2 scaffold and iodide deposition [38]. Snaith removed scaffoldingfrom the device and applied planar structure, obtaining similar conversion efficiency comparedwith the report by Burschka et al [39]. Subsequently, efficiencies of 16.2% and 17.9% were17
Queensland University of Technologyreported by Seok et al. in early 2014 by using CH3NH3PbI3-xClx and a poly-triarylamine HTM[40-41]. In 2016, Saliba introduced a perovskite solar cell with an efficiency of 21.1% by usinga mixture of triple cation (Cs/MA/FA). It showed high stability and reproducibility [42]. Seokand co-workers introduced an approach to reduce defects in the perovskite layer by using anintramolecular exchanging process in 2017, which is favorable in reducing the defectsconcentration, and they obtained an efficiency of over 22% [43].1.4 SCAPS-1D Based Numerical SimulationNumerical simulation is a crucial and efficient way to investigate the physical mechanism in asolar cell device without actually making the device. It can save both time and money in devicedevelopment. Much simulation software has been developed and applied in the research ofsolar cell devices such as AMPS-1D, SCAPS-1D, PC1D, AFORS-HET and so on. SCAPS-1Dis a one-dimensional simulation software developed by the University of Gent, Belgium. It hasbeen applied to the study of different types of solar cells such as CZTS, CdTe, CIGS, etc. [4347]. Compared with other software, SCAPS has a very intuitive operation window anddiversified models for grading, defects and recombination. The main features of SCAPSincluding [48] materials and defects properties can be defined in 7 semiconductor layers, asshown in Fig.1.10 and Fig.1.11, where plentiful grading laws are provided for almost allparameters of materials and defects, and the defect definition can be set in both bulk andinterface. There are five defect types and distributions available in the software and a varietyof properties related with solar cells, such as energy bands, concentrations, currents, I-Vcharacteristics, C-V, C-f, and QE can be determined by SCAPS. SCAPS can also provide18
Queensland University of Technologyflexible calculation and record functions including single shot, batch calculation, curve fitting,data and diagram recording.Fig.1.10 Layer definition panel in SCAPS-1DFig.1.11 Material and defect definition panel in SCAPS-1D19
Queensland University of Technology1.4.1 Basic Semiconductor Physics in SCAPS-1Dl Basic EquationsPoisson’s equation is used to describe the relationship between potential and space charges, asshown in Eq.1.03TU(TV U𝜑 𝑥 [𝑛 𝑥 𝑝 𝑥 𝑁\] (𝑥) 𝑁O (𝑥) 𝑝 𝑥 𝑛 (𝑥)]Y(1.03)where, 𝜑 is the potential, q is the elementary charge, 𝜀 is the permittivity, n is the density offree electron, p is the density of free hole, 𝑁\] is the ionised donor-like doping density, 𝑁O is the ionised acceptor-like doping density, 𝑝 is the trapped hole density, 𝑛 is the trappedelectron density.Continuity equations Eq1.04 -1.05 define the transportation of carriers𝑞𝑞TLTTeT TbI 𝑞𝐺 𝑞𝑅TVTbf TV 𝑞𝐺 𝑞𝑅(1.04)𝐽L 𝑞𝑛𝜇L𝐽e Tj 𝑞𝐷LTVTj 𝑞𝑝𝜇eTV TLTVTe𝑞𝐷eTV(1.05)where, G is the optical generation rate, R is the recombination rate, 𝐷L is the electron diffusioncoefficient, 𝐷e is the hole diffusion coefficient,𝜇L is the electron mobility, and 𝜇e is thehole mobility.l Concentration for Electrons and HolesIn thermal equilibrium, the free carrier concentrations are expressed by Eq.1.06-1.07𝑛 𝑁# exp(𝑝 𝑁q exp(op oC%& 'or op%& ')(1.6))(1.7)where, Ef is Fermi level, 𝑘2 is Boltzmann constant, T is temperature, Ec and Ev are energylevels under a steady state.20
Queensland University of Technologyl Diffusion LengthDiffusion length describes the transport ability of carriers in a solar cell device. It depends ondiffusion coefficient and carrier lifetime, which is shown in Eq.1.09𝐿 𝐷𝜏(1.09)where, L is diffusion length, 𝜏 is carrier lifetime.l Recombination MechanismThere are three recombination models used in SCAPS.Band-to-band recombination is a reverse process of photon absorption. The electrons in theconduction band drop back down to the empty valence band and recombine with holes. Theband-to-band recombination rate can be expressed as:𝑅 𝛾(𝑛𝑝 𝑛Ku )(1.10)The Shockley-Read-Hall (SRH) recombination is also called trap-assisted recombination. Itoccurs due to the defects or impurities in the materials. The SRH recombination rate can begiven by:𝑅 Le LHUvf L]L- ]vI (e]e- )(1.11)Auger recombination is a process when a pair of electron and hole recombination occurs duringthe transition from high energy level to low energy level, with the resulting energy being givento the third carrier. It can be described by:𝑅 (𝑐LO 𝑐eO )(𝑛𝑝 𝑛Ku )(1.12)where, R is recombination rate, 𝛾 is recombination coefficient, 𝜏L and 𝜏e are lifetimes forelectron and hole. 𝑛6 and 𝑝6 are equilibrium electron concentration and equilibrium holeconcentration, 𝑐LO and 𝑐eO are constants, which can be set in SCAPS.21
Queensland University of Technologyl Work FunctionWork function is the minimum energy required to move an electron from a solid to vacuum.The value of work function is used to describe the strength of binding energy of an electron inmaterials. In SCAPS, work function can be set by the user, or it can be calculated by using themodel in SCAPS, as shown in Eq.1.13-1.15n-type contact:𝜙y 𝜒 𝑘2 𝑇𝑙𝑛(} } } )(1.13)p-type contact:𝜙y 𝜒 𝐸‚ƒe 𝑘2 𝑇𝑙𝑛(} } } ) (1.14)intrinsic contact:}𝜙y 𝜒 𝑘2 𝑇𝑙𝑛( )LH(1.15)where, 𝜙y is work function, 𝜒 is electron affinity, Nc is effective density of state forconduction band, NA and ND are acceptor
Since then, research on solar cells has entered the third generation. Perovskite solar cells (PSCs) are derived from the research concept of dye-sensitized solar cells. 1.2.1 Working Mechanism in Solar Cells Solar cells are made by semiconductor materials, which can generate electricity from sunlight directly by using a photovoltaic effect.
the economic viability of solar energy. A great contender in advancing photovoltaics are perovskite solar cells. Perovskite solar cells have increased their efficiency from 3.8% in 2009 to 22.7% in late 20172. Perovskite solar cells have the potential to achieve higher efficiencies at very low production costs.
21% ferropericlase, and 7% CaSiO 3 perovskite by weight. Al-bearing (Mg,Fe)SiO 3 perovskite is also the most abundant phase in a MORB composition above 26 GPa, coexisting with an SiO 2 phase, CaSiO 3 perovskite, and a Ca-ferrite-type Al phase (e.g. Hirose et al. 2005). The perovskite to post-perovskite phase transition takes place in MORB .
SUNCAT Center for Interface Science and Catalysis Department of Chemical Engineering Stanford University Stanford, CA 94305, USA Hysteresis-Free Perovskite Solar Cells Perovskite solar cells (PSCs) have emerged as a promising next generation of solar cells, as their power conversion efficie
solar cells (PSC) are introduced from dye-sensitized solar cells (DSSCs), the presence of a perovskite capping layer as opposed to a single dye molecule (in DSSCs) changes the interactions between the various layers in perovskite solar cells. 4-tert-butylpyridine (tBP), commonly used in PSCs, is assumed to function as a charge
solar cells, and perovskite solar cells each, from their prototypes to recent results. As we go along, the science and prospects of the application of solar cells will be discussed. 1. Single-walled Carbon Nanotubes as the Photoactive Material in Solar Cells SWNTs provide an ideal light-harvesting medium that has a wide range of direct band .
Once completed this deposition, the chamber was vented with dry N2 to replace the p-HTL crucibles with those containing the starting materials for the perovskite deposition, PbI2 and CH3NH3I. The vacuum chamber was evacuated again to a pressure of 10-6 mbar, and the perovskite films were then obtained by co-deposition of the two precursors.
sources and solar cells o er one of the best solutions [1]. The current market of photovoltaics are dominated by inorganic solar cells such as silicon solar cells [2]. Silicon is considerably used in bulk (1st generation), thin- lm (2nd generation), and some of the nano-structured (3rd generation) solar cells [1]. However, the e ciencies
Alfredo López Austin viene del Norte, de Chihuahua, de Ciudad Juárez, para mayor precisión. Nació en aquellas regiones de desiertos y climas extremos que fraguan de manera tan peculiar el espíritu de quienes ven el mundo por primera vez en esas latitudes. La primera parte de la vida de mi maestro fue muy rica, envidiablemente rica en experiencias. Cuando recuerdo alguno de los pasajes de .
