CZTS Thin Film Solar Cells Research Articles

Thickness Optimization of Various Layers of CZTS Solar Cell

Thin film solar cells based on Cu2ZnSnS4 (CZTS) absorbers are proposed with the structure glass/Mo/CZTS/buffer/ZnO. In this work we have simulated CZTS thin film solar cell using solar cell capacitance simulator (SCAPS). The influences of thickness of (CZTS) absorber, thickness of (CdS) buffer layer and Zinc oxide window Layer (ZnO) on the photovoltaic cell parameters are studied. It can be seen after reviewing the results, that for high conversion efficiency, the cell should have a thin (...)

Improvement of Mo/Cu2ZnSnS4 interface for Cu2ZnSnS4 (CZTS) thin film solar cell application

ABSTRACTThe focus of this work is on back contact improvement for sputtered CZTS thin film solar cells. Three methods have been investigated including a thin Ag coating, a thin ZnO coating on the Mo back contact and rapid thermal annealing of the back contact. All of these methods have been found to reduce defects such as voids as well as secondary phases at the back contact region and inhibit the formation of MoS2. Consequently all the mothods effectively enhances Voc, Jsc, FF and therefore efficiency significantly.

Development of Earth-abundant CZTS Thin Film Solar Cells with Sulfurization Technique

ABSTRACTCu2ZnSnS4 (henceforth CZTS) absorber layers are successfully synthesized by a sulfurization technique of physical vapor deposited precursors. In our previous report, we have clarified that the off-stoichiometry composition of Cu-poor and Zn-rich is desirable to achieve high conversion efficiency. By using CZTS compound target that provide such active composition, we could conduct a simple single sputtering method to prepare CZTS absorber. In our laboratory, a two-stage process of precursor preparation followed by sulfurization is a major fabrication method from the start of this study. We think that this method is suitable for a mass production. An optimization of the sulfurization process is a quite important issue because the active composition was already revealed. In this paper, TG/DTA system available in the H2S atmosphere is introduced to optimize the sulfurization condition. As a result, bump-free CZTS films were prepared successfully and the fluctuation of J-V properties in one substrate was drastically suppressed.

Characterization of a CZTS thin film solar cell grown by sputtering method

We report the performance of Cu2ZnSnS4 (CZTS) thin film solar cell that showed efficiency in the range of 6.2% without an anti-reflection coating. Initially, the CZTS precursor film was co-sputtered using three different targets; copper (Cu), tin sulfide (SnS) and zinc sulfide (ZnS). The Cu target was subjected to DC power, and RF power was used for the SnS and ZnS targets. The as-grown CZTS film was sulfurized in a H2S/N2 environment at 525°C, which re-crystalized the film with grain sizes in the range of 1μm. Cadmium sulfide (CdS) was used as the n-type layer. Current–voltage (I–V), quantum efficiency (QE) and capacitance–voltage (C–V) measurements were used to characterize the cell device. The modeling and analysis of QE and CV data showed that a significant portion of the CZTS layer did not contribute to the photo-generation. Optimizing CZTS phase purity, improving QE in the broader wavelength region, and increasing minority carrier lifetime are necessary steps to further improve CZTS device performance.

Effects of sulfurization temperature on CZTS thin film solar cell performances

Synthesis of Cu2ZnSnS4 thin film solar cells by sulfurization of sputtered Sn/Zn/Cu precursors is studied. The sulfurization temperatures were varied, and the morphology, cross section, and composition of the CZTS were investigated by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction and Raman scattering. To further explore the CZTS layer, the following additional layers were deposited to complete the solar cells: CdS with chemical bath deposition; ZnO and AZO with RF magnetron deposition; and, finally, silver fingers as the front contact. The efficiency and characteristics of the thin film solar cells were measured and a detailed comparison is reported. Sulfurization at 550°C yields a maximum efficiency of 5.75% without any anti-reflective layers.

One-step deposition of Cu2ZnSnS4 thin films for solar cells

A simple one-step chemical bath process was developed to fabricate Cu2ZnSnS4 (CZTS) thin films. Effects of pH value and ZnCl2 precursor content on the formation of CZTS were investigated. The best process parameters were a pH value of 3.5–4 and a ZnCl2 content of 1.75mmoL for deposition of high quality of CZTS films. The films consist of kesterite phase CZTS nanocrystals and exhibit a band-gap of ∼1.48eV. A conversion efficiency of 0.30% was achieved in one of the CZTS thin film solar cells. The route developed here may provide an alternative approach to produce low-cost and large area solar cells.

Study of the junction and carrier lifetime properties of a spray-deposited CZTS thin-film solar cell

The Cu2ZnSnS4 (CZTS) thin-film solar cell fabricated entirely by a spray pyrolysis process was investigated under diffused white light in the present study. A CdS layer was developed as a heterojunction partner. The structural, morphological and photovoltaic characterization of an as-prepared stoichiometric CZTS film was carried out. The diode ideality factor n was found to be in the range of 1.2–5.6 in the forward bias region and it is explained by the Frenkel–Poole conduction model. The solar cell exhibited open-circuit voltage (Voc) of 157.25 mV, short-circuit current density (Jsc) of 3.024 mA cm−2 and fill factor (FF) of 24.77% at an incident irradiance of 200 W m−2 from the white LED source. The effective minority carrier lifetime of 263 μs was confirmed by the open-circuit voltage decay fitting under pulsed monochromatic LED excitation.

CZTS based thin film solar cells: a status review

Today’s thin film photovoltaic technologies comprising CuInS2 (CIS), CuInGaSe2 (CIGS) and CdTe rely on elements that are costly and rare in the earth’s crust (e.g. In, Ga, Te) and are toxic (e.g. Cd). Hence, in future cost reduction and increased production, using abundantly available non-toxic elements, seem to be the main issues. Cu2ZnSnS4 (CZTS), having the kesterite structure, is one of the most promising absorber layer candidates for low cost thin film solar cells, because of its suitable direct band gap between 1·4 and 1·5 eV and large absorption coefficient, over 104 cm−1. Also it is composed of earth abundant and non-toxic elements, promising price reductions in future. Recently, research in this area has gained momentum due to the desirability of producing Ga, In and Cd free absorber layers and the potential to obtain new insights. Hence, a review of recent literature is urgently warranted. The CZTS progress and present status of CZTS thin film solar cells has been reviewed, with the hope of identifying new paths for productive research.

Preparation and Characterization of Cu2ZnSnS4 Thin Films and Solar Cells Fabricated from Quaternary Cu-Zn-Sn-S Target

CZTS thin films were fabricated through sputtering from a quaternary Cu-Zn-Sn-S target, followed by a sulfurization process. CZTS thin-film solar cells were also fabricated and a highest efficiency of 4.04&#x25; was achieved. It has been found that obvious Zn loss occurs during the sputtering and poorly crystallized CZTS are formed in the sputtered films. The Zn loss leads to the appearance of SnS. A sulfurization process can obviously improve the crystallinity of CZTS and films with grain size of several hundred nanometers can be obtained after sulfurization. The optical band gap of the films is estimated to be 1.57&#x2009;eV. The electrical properties of the 4.04&#x25; efficient solar cell were investigated and it has been found that cell has obvious deficiency in minority carrier lifetime. This deficiency should be responsible for the low <svg style="vertical-align:-3.39064pt;width:18.012501px;" id="M1" height="15.4" version="1.1" viewBox="0 0 18.012501 15.4" width="18.012501" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(.017,-0,0,-.017,.062,11.112)"><path id="x1D43D" d="M434 650l-5 -28q-60 -8 -75 -20.5t-25 -69.5l-71 -395q-20 -107 -57.5 -168t-106.5 -94q-40 -18 -61 -20l-10 32q77 23 113 108q21 50 41 160l68 377q10 57 -1.5 69.5t-76.5 20.5l6 28h261z" /></g> <g transform="matrix(.012,-0,0,-.012,7.825,15.187)"><path id="x73" d="M319 325l-25 -7q-33 99 -103 99q-29 0 -47 -19.5t-18 -49.5t22 -49.5t62 -36.5q63 -26 95 -57t32 -79q0 -64 -50 -101t-115 -37q-35 0 -67.5 10.5t-46.5 23.5q-5 11 -11 51t-6 67l27 5q14 -53 46.5 -88.5t75.5 -35.5q29 0 50 19.5t21 50.5t-19.5 51.5t-59.5 39.5&#xA;q-28 12 -46 22.5t-38.5 27t-30.5 38.5t-10 49q0 54 42.5 92t109.5 38q48 0 88 -18q6 -15 13 -50.5t9 -55.5z" /></g><g transform="matrix(.012,-0,0,-.012,12.287,15.187)"><path id="x63" d="M390 111l17 -21q-34 -45 -80 -73.5t-89 -28.5q-91 0 -146 62t-55 147q0 118 101 195q74 57 149 57h1q59 0 90 -27q16 -14 16 -30q0 -15 -12 -29t-21 -14q-8 0 -19 11q-44 41 -101 41q-52 0 -87.5 -42.5t-35.5 -117.5q0 -49 15 -87t39 -58t49 -30t48 -10q33 0 60.5 12&#xA;t60.5 43z" /></g> </svg> and low <svg style="vertical-align:-3.39064pt;width:24.575001px;" id="M2" height="15.4" version="1.1" viewBox="0 0 24.575001 15.4" width="24.575001" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(.017,-0,0,-.017,.062,11.112)"><path id="x1D449" d="M730 650l-8 -28q-52 -4 -72 -18t-64 -77q-79 -113 -321 -539h-33l-119 541q-13 59 -29.5 73t-66.5 20l7 28h245l-8 -28l-28 -5q-33 -6 -40.5 -15.5t-0.5 -38.5l102 -450h2q191 320 246 430q21 42 15.5 56t-43.5 19l-31 4l7 28h240z" /></g> <g transform="matrix(.012,-0,0,-.012,12.675,15.187)"><path id="x6F" d="M257 449q92 0 154 -65t62 -158q0 -112 -67 -175t-150 -63q-98 0 -158.5 66.5t-60.5 154.5q0 59 21 106.5t54.5 75.5t71 43t73.5 15zM244 416q-48 0 -81 -47t-33 -128q0 -96 38 -158t99 -62q51 0 82 43.5t31 139.5q0 91 -36 151.5t-100 60.5z" /></g><g transform="matrix(.012,-0,0,-.012,18.85,15.187)"><use xlink:href="#x63"/></g> </svg> of our cell.

Selective Front Side Patterning of CZTS Thin-Film Solar Cells by Picosecond Laser Induced Material Lift-Off Process

Abstract The thin-film Cu-chalcopyrite based solar cell technologies become more attractive due to their lower cost and optimal performance. Efficiency of cells with a large area might be maintained if small segments are interconnected in series in order to reduce photocurrent in thin films and resistance losses, and laser scribing is crucial for performance of the device. We present our results on the material lift-off effect investigations in the CZTS thin-film solar cell structures which can be applied for the damage-free front-side scribing processes. The results of the P2 and P3 type scribe formation with the fundamental harmonics of a picosecond laser are presented.

Studies of compositional dependent CZTS thin film solar cells by pulsed laser deposition technique: An attempt to improve the efficiency

The performance of CZTS thin films deposited by using pulsed laser deposition technique is investigated as a function of target composition. The chemical composition ratio a=Cu/(Zn+Sn) of the target material has been varied from 0.8 to 1.2 in step of 0.1 by keeping Zn/Sn constant. The effect of the chemical composition in the precursor thin films on the structural, morphological, chemical and optical properties of the CZTS thin films has been investigated. X-ray diffraction and X-ray photoelectron spectroscopy studies showed that the annealed CZTS thin films are of a single kesterite crystal structure without any other secondary phases. The direct band gap energy of the CZTS thin films is found to decrease from 1.72–1.53eV with increase of ‘a’. The estimated band-gap energy from the quantum efficiency measurements is about 1.54eV. The solar cell fabricated with Glass/Mo/CZTS/CdS/ZnO:Al/Al structure grown using [a=Cu/(Zn+Sn)=1.1] showed the best conversion efficiency of 4.13% with Voc=700mV, Jsc=10.01mA/cm2 and FF=0.59.

Development of Kesterite Cu2ZnSn(S1-x,Sex)4 (CZTSS)-Based Thin Film Solar Cells with In and Ga Free Absorber Materials

Chalcogenide-based semiconductors, such as CuInSe2, CuGaSe2, Cu(In,Ga)Se2 (CIGS), and CdTe have attracted considerable interest as efficient materials in thin film solar cells (TFSCs). Currently, CIGS and CdTe TFSCs have demonstrated the highest power conversion efficiency (PCE) of over 11% in module production. However, commercialized CIGS and CdTe TFSCs have some limitations due to the scarcity of In, Ga, and Te and the environmental issues associated with Cd and Se. Recently, kesterite CZTS, which is one of the In- and Ga- free absorber materials, has been attracted considerable attention as a new candidate for use as an absorber material in thin film solar cells. The CZTS-based absorber material has outstanding characteristics such as band gap energy of 1.0 eV to 1.5 eV, high absorption coefficient on the order of 104cm-1, and high theoretical conversion efficiency of 32.2% in thin film solar cells. Despite these promising characteristics, research into CZTS-based thin film solar cells is still incomprehensive and related reports are quite few compared to those for CIGS thin film solar cells, which show high efficiency of over 20%. The recent development of kesterite-based CZTS thin film solar cells is summarized in this work. The new challenges for enhanced performance in CZTS thin films are examined and prospective issues are addressed as well.

Investigating the Role of Grain Boundaries in CZTS and CZTSSe Thin Film Solar Cells with Scanning Probe Microscopy

Scanning Kelvin probe microscopy (SKPM) measurements reveal a higher positive surface potential at the grain boundaries (GBs) as compared to the grain while conductive atomic force microscopy (C-AFM) measurements show higher current flow in the vicinity of the GBs of Cu2ZnSnS4 (CZTS) and Cu2ZnSn(S,Se)4 (CZTSSe). These results demonstrate the enhanced minority carrier collection taking place at the GBs of CZTS and CZTSSe.

Development of CZTS thin films solar cells by pulsed laser deposition: Influence of pulse repetition rate

► Development of CZTS thin film solar cell by PLD . ► Structural optical compositional and morphology properties of CZTS thin films. ► Influence of pulse repetition rate on physicochemical properties CZTS thin films. High-quality Cu 2 ZnSnS 4 (CZTS) thin films were synthesized by pulsed laser deposition as a function of pulse repetition rate onto the SLG substrates. Influence of pulse repetition rate onto the structural, morphological, compositional and optical properties have been investigated for as-deposited and annealed thin films. X-ray diffraction study shows transformation of amorphous to crystalline phase after tuning pulse repetition rate and annealing of samples. FESEM images of thin films show increase in grain size upon annealing. Films are nearly stoichiometric deposited at 10 Hz repetition rate has been confirmed with the help of EDAX and XPS analysis. The direct band gap energy of the deposited CZTS thin films are in the solar energy range. The performance of solar cell based on CZTS absorber layer has been tested and the efficiency is about 2%.

Formula omitted] thin film solar cells prepared by non-vacuum processing

Cu 2 ZnSnS 4 (CZTS)-based solar cell devices were prepared entirely by non-vacuum deposition techniques on soda lime glass (SLG) substrates. The ZnO:Al window, CdS buffer and CZTS absorber layers of the Al/ZnO:Al/CdS/CZTS/Mo/SLG solar cell structure were deposited by sol–gel method, chemical bath deposition method and sol–gel sulfurizing method, respectively. The best solar cell sample showed an open-circuit voltage of 390 mV, a short-circuit current density of 7.8 mA / cm 2 , a fill factor of 0.33 and an efficiency of 1.01% under irradiation of AM 1.5 and 100 mW / cm 2 . This is the first report on CZTS thin film solar cells in which all the semiconductor layers were prepared under non-vacuum condition.

Cu2ZnSnS4 Thin Films Annealed in H2S Atmosphere for Solar Cell Absorber Prepared by Pulsed Laser Deposition

Cu2ZnSnS4 (CZTS) precursors were prepared by pulsed laser deposition while controlling the energy density to eliminate grains of Cu–Sn–S compounds. The precursor prepared with an energy density of 0.7 J/cm2 was flat and of better quality than the precursor prepared with an energy density of 1.5 J/cm2. The precursors were annealed in N2+H2S (5%) atmosphere. As a result of annealing, the decrease of the compositional ratio of sulfur was suppressed and the films became nearly stoichiometric. Some peaks in the an X-ray diffraction pattern of thin films are attributed to (112), (220), (312), and (200) planes of CZTS. The direct band-gap energy of the film annealed at 500 °C was about 1.5 eV, which is very close to the optimum value for a solar-cell absorber, and hence was used for a solar cell. The CZTS thin film solar cell with an active area of 0.12 cm2 showed an open-circuit voltage of 336 mV, a short-circuit current of 6.53 mA/cm2, a fill factor of 0.46, and a conversion efficiency of 0.64%.

Fabrication of Cu2ZnSnS4 Thin-Film Solar Cell Prepared by Pulsed Laser Deposition

A thin-film solar cell based on a Cu2ZnSnS4 (CZTS) absorber layer deposited by pulsed laser deposition has been fabricated with an Al:ZnO (n-type) window layer and a CdS buffer layer. Some peaks attributed to (112), (200), (220), and (312) planes of CZTS appeared in an X-ray diffraction pattern of a thin film. The composition of the film was Sn-rich and the band gap energy was approximately 1.5 eV. A CZTS film annealed at 500 °C in an atmosphere of N2 had optical characteristics suitable for use in an absorber layer of a thin-film solar cell and was used for a solar cell. The CZTS thin-film solar cell with an active area of 0.092 cm2 showed an open-circuit voltage of 546 mV, a short-circuit current of 6.78 mA/cm2, a fill factor of 0.48, and a conversion efficiency of 1.74%.

Cu 2ZnSnS 4-type thin film solar cells using abundant materials

The development of environment friendly type thin film solar cell Cu 2ZnSnS 4 (say CZTS-type) fabricated using abundant materials is introduced in this paper. Three RF sources co-sputtering continued with vapor phase sulfurization method (inline-type vacuum apparatus) is utilized. Those processes were sequentially done in different apparatus in our previous work. In this study, an inline-type vacuum apparatus is firstly introduced to acquire higher quality of CZTS films. Inductively Coupled Plasma Spectroscopy (ICPS) is used to analyze the minute material composition of CZTS thin film solar cell. By optimizing the material composition, 5.74% of conversion efficiency is obtained. It is the best data for CZTS-type thin film solar cells at present.