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Summary: In recent years, the laser half‐cutting technology for silicon solar cells has gotten much attention from researchers for increasing module power and would become particularly important in the photovoltaic modules domain. Herein, this paper would introduce a kind of new laser cutting process, a thermal laser separation (TLS) cutting technology. In the laser cutting processes, the influence on mechanical and electrical characteristics of bifacial p‐type passivated emitter and rear (PERC) solar cell and module were investigated in considerable detail. We have made a series of research and analyses including the cutting principle, opening length, fracture surface, and hot influence zone. The results reveal that the TLS cutting process could reduce damage more than the regular laser scribing and cleaving (LSC) cutting process. The TLS cutting process would achieve the higher power of a PERC half‐cutting bifacial module and the stronger bending strength of half solar cells than the LSC cutting process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Random inverted pyramid textured PDMS films are prepared by a simple process. • They are used as radiative cooling emitters for heat dissipation of solar cells. • The transparency and cooling power are both improved by the texturing treatment. • A temperature drop of 17 ℃ and an efficiency rise of 1.02% of the cells are shown. • Surface texturing treatment also improves the hydrophobicity of PDMS films. Radiative cooling is a promising passive cooling phenomenon. For the heat dissipation of silicon solar cells, radiative cooling emitters require high transmittance in the wavelength range of 300–1100 nm and high emissivity in the range of 8–13 μm. In this paper, a simple and low-cost coating and embossing process is proposed to texture the surface morphology of the PDMS film. A radiative cooling emitter is prepared with a random inverted pyramid-like light-trapping structure on the surface. The experimental results show that the transparency and radiative cooling performance of textured polydimethylsiloxane films are improved by 2.1% and 2.7%, respectively. When using a polished Al mirror as the substrate, the radiative cooling temperature difference and net radiative cooling power are increased to 12.8 ℃ and 103 W·m−2, respectively. By employing it as a solar cell radiator, the radiative heat dissipation power of the solar cell is increased by 67 W·m−2, and the working temperature is reduced by over 17 ℃. An improvement in photoelectric conversion efficiency of 1.02% is achieved. It is demonstrated that the texturing treatment also improves the hydrophobicity of the polydimethylsiloxane film. The film is more applicable for radiative cooling emitters that are directly exposed to the atmosphere in outdoor environments. [ABSTRACT FROM AUTHOR]

In this work, ZnO/Ag(Cu doped)/ZnO and ZnO/(Cu doped) Ag/ZnO/SiO2 multilayer films are prepared on glass by a sputtering technique. The optical, structural, and morphological properties of the Ag-based multilayer structures are compared. According to the results of the transmittance curve, it is found that the Cu doping into Ag leads to a significant broadening of the transmittance spectrum of the multilayer. The performance of the multilayer largely depends on the deposition time of different films. After doping with copper, the average light transmittance of the multilayer film exceeds 81.2% from 380 to 1100 nm, and the average light transmittance exceeds 10.2% from 1100 to 2500 nm. When the SiO2 anti-reflection layers are introduced, the average light transmittance of the multilayer structure from 380 to 1100 nm exceeds 85.2%, and this value reaches 18.3% from 1100 to 2500 nm. In addition, a 6-inch ZnO/Ag(Cu doped)/ZnO/SiO2 multilayer is used as the cover layer of the silicon solar cell. After 2 h of sunlight exposure, the increase in working temperature is reduced by 12 °C while the open-circuit voltage reduction is reduced by 4.1% in comparison with that using standard glass. [ABSTRACT FROM AUTHOR]

• SiO 2 nanospheres were used for more uniform phosphorus diffusion. • An enhancement of minority carrier lifetime from 42 μs to 56 μs was obtained. • A small square resistance of 22 Ω/sq was made at high phosphoric acid concentration. • The efficiency in the cell center was enhanced by 40.54% using the nanospheres. In order to improve the quality of n+ emitter fabricated by phosphorus doping, SiO 2 nanospheres were added into a phosphoric acid solution for spin-on doping. Through a complete analysis of the trade-off between the diffusion uniformity and sheet resistance, the particle size of SiO 2 nanospheres is selected to be 230 nm. It is found that with the increase of phosphoric acid concentration from 50% to 85%, the average sheet resistance decreases from 128.5 Ω/sq to 18.1 Ω/sq, and the diffusion uniformity increased from 95.2% to 98.5%. In a large concentration range, the surface doping concentration of the emitter will increase with phosphoric acid, but when the concentration of phosphoric acid reaches 80%, the surface doping concentration will be almost unchanged. Nevertheless, different from above, the p-n junction depth has little dependence on the phosphoric acid concentration. Moreover, the efficiencies in the solar cell center and edge are enhanced by 40.54% and 88.08% respectively using SiO 2 nanospheres assisted diffusion. [ABSTRACT FROM AUTHOR]

• Doped poly-Si/SiO x passivation was used for front side of p-type PERC cell. • Obvious passivation effect was obtained in the PERC cells with the poly-Si/SiO x. • Dark recombination current density was reduced to about 3 fA/cm2 in test sample. • An enhanced V oc value of 10 mV was achieved in the passivated p-type PERC cell. The most promising and feasible approach to achieving high-efficiency silicon solar cells must be passivation contact compatible with current homojunction thermal processes. In this paper, an easy-to-implement carrier-selective passivation contact with doped poly-Si/SiO x for produing p-type passivated emitter and rear cell (PERC) was proposed. The passivation contact structure consisted of an ultra-thin SiO x layer capped with an intrinsic amorphous silicon (a-Si) layer prepared by low pressure chemical vapor deposition, which was deposited onto a p-type silicon substrate and then was doped and re-crystallized by a thermal phosphorus diffusion at 850 °C for 75 min. By optimizing the diffusion profile and cleaning time, a low dark recombination current density J 0 ≈ 3 fA/cm2 and large minority carrier lifetime of 3000 μs were achieved on the 180-μm-thick n-type wafers with a resistivity of 3 Ω·cm, corresponding to an implied open-circuit voltage of 700 mV. P-type PERC cells with the highly doped poly-Si/SiO x passivated emitter demonstrated 683.97 mV of open-circuit voltage, showing more than 10 mV enhancement comparing with regular PERC cells. The results demonstrated an attractive potential of the carrier-selective passivation contacts with doped poly-Si/SiO x under front metallizatin area in photovoltaic application. [ABSTRACT FROM AUTHOR]

Sputtering followed by selenization is one of the most common methods for preparing CZTSSe thin films. However, the influence of selenium partial pressure on the crystallinity of the CZTSSe film has been rarely reported. In this study, CZTSSe thin films were prepared by selenization using quartz tubes of different lengths. The influence of Se saturated vapor pressure and temperature on the structure, composition, optical, and electrical properties of CZTSSe films and solar cells was analyzed and these results were used to optimize the performance of the CZTSSe film. It was found that the maximum partial pressure of selenium was 22,542 Pa when the selenization process was carried out in a quartz tube with a length of 30 cm, which largely improved the structural and electrical properties of CZTSSe. However, quartz tube with an over-short length would bring strong partial pressure during selenization, which resulted in a generation of secondary phases. Finally, CZTSSe thin-film solar cell with a maximum efficiency of 3.27% was obtained at an optimal selenium partial pressure of 22542 Pa. [ABSTRACT FROM AUTHOR]

Mono-like cast silicon (ML C-Si) passivated emitter and rear cell (PERC) solar cells with high performance and low price are becoming popular in the modern PV market. In this work, mono-like cast silicon PERC solar cells with B and Ga co-doping were treated by single current injection annealing (CIA) process and double CIA process. According to Light-induced degradation (LID) effect analysis, it was found that both single CIA process and double CIA process would enhance the electrical properties of the solar cells. After a light soaking treatment for 60 kWh, the efficiency of the solar cells treated by single CIA process decreased by 1.96% comparing with that before the CIA process. In contrast, the efficiency of the solar cells treated by double CIA process decreased by only 1.13%. All the results, including changes in other electrical properties of solar cells, showed that double CIA process would effectively enhance the anti-LID effect of ML C-Si PERC solar cells. [ABSTRACT FROM AUTHOR]

The troublesome residual stress is always a stumbling block that drags the progress pace of flexible CZTSSe thin film solar cells, which urgently needs to be noticed and solved. In this paper, low-temperature prepared CZTSSe absorber with relieved residual stress (0.558 GPa) is realized by Sb incorporation. Owing to the evaporated 20 nm Sb layer under CZTS precursor, the crystalline quality and band mismatching of CZTSSe/CdS interface are simultaneously improved. Additionally, the spatial potential fluctuation extracted from the PL results is found to decrease from 63.26 meV to 41.57 meV, indicating a reduction in band tailing and disorder of CZTSSe absorber. Compared with the general solar cells fabricated at 580 °C, flexible devices with Sb incorporation can maintain a slightly higher performance at a lower temperature about 60 °C. The best power conversion efficiency (PCE) of 4.41% is obtained in the solar cell with 550 °C-selenized CZTSSe absorber after incorporating 20 nm Sb layer, featuring 351.20 mV Voc, 25.73 mA/cm2 Jsc and 48.79% FF. Finally, low-temperature prepared flexible CZTSSe thin film solar cell can retain over 83% of the original PCE after bending at 180° for 40 cycles. The mechanical durability paves a promising way for flexible CZTSSe thin film solar cell in roll-to-roll production. [ABSTRACT FROM AUTHOR]

• Evaporated Sb layer was inserted into CZTSSe precursor for the first time. • Hole concentration in CZTSSe was found to increase with Sb layer thickness. • The grain growth of CZTSSe benefited a lot from the introduced Sb layer. • The electrostatic potential fluctuation was reduced after the incorporation of Sb. • 20 nm evaporated Sb layer took effect to the fullest extent in PCE enhancement. Cu 2 ZnSn(S,Se) 4 (CZTSSe) chalcogenide with natural-abundance, environment -friendly and impressive photovoltaic performance is promising material for kesterite thin film solar cell. In this paper, the effects of evaporated Sb layer on performance of flexible CZTSSe thin film solar cell are investigated. Systematic studies show that the quasi-liquid Sb 2 Se 3 plays productive roles in promoting grain growth, subsequently volatilizes in the elevated selenization temperature without entering into the CZTSSe lattice. Obvious improvements in crystallinity, grain size, surface roughness, hole concentration and device performance are obtained after optimizing the thickness of Sb layer. The electrostatic potential fluctuation extracted from the PL results is found to decrease from 115.9 meV to 60.7 meV after introducing 20 nm evaporated Sb layer. Finally, 20 nm evaporated Sb layer takes effect to the fullest extent which shows a 69% increase in photoelectric conversion efficiency (PCE). The incorporation of Sb opens up access to opportunity in roll-to-roll process for thin film solar cells. [ABSTRACT FROM AUTHOR]

In this work, antimony selenide (Sb2Se3) thin films were prepared using electron-beam (e-beam) evaporation followed by selenization process (two-step method) for the first time. The effect of selenization temperature on the properties of Sb2Se3 thin films and solar cells was investigated systematically. Formation of pure polycrystalline Sb2Se3 was confirmed and the intensity of (hk1) and (hk2) patterns was found to decrease while that of (hk0) to increase with temperature elevating. However, when the temperature became higher than 360 °C, the shape of Sb2Se3 grains gradually changed to rod-like shape from round shape and some craters and cracks in the films can be observed. Sb2Se3 films prepared at 360 °C showed an average grain size of 450 nm, a roughness of 42 nm, an optical bandgap of 1.24 eV and a carrier concentration of 4.99 × 1012 cm−3. The corresponding Sb2Se3 solar cells exhibited an optimal power conversion efficiency of 1.15%. Our results demonstrated that the process of e-beam evaporation of Sb followed by selenization at appropriate temperature is a good way to prepare high quality Sb2Se3 thin films for solar cells. [ABSTRACT FROM AUTHOR]

In this paper, the one-step Cu-assisted chemical etching method is reported for controllable thinning and texturization on mono-crystalline silicon in Cu2+/HF/H 2 O 2 mixture solution. HF and Cu2+ exhibited a synergetic effect on accelerating etching process while H 2 O 2 slowed down the preferential Si (100) etching by oxidizing the Cu atoms. Within optimal 0.15 M Cu2+/4 M HF/0.88 M H 2 O 2 solution, quasi-inverted pyramid-like structures of 2–4 μm in size and a reflectance of 8.46% were obtained at 20 °C. By adjusting the temperature and etching time, ultra-thin silicon wafers with thickness of 19–120 μm were fabricated. Comparing the microstructures obtained at 20 °C and 60 °C, widths and inclination angles were distinct. By illustrating the transportation and distribution of holes during the etching process, the intrinsic connection between thinning and texturization was studied. The etching results, including etching rates and morphologies, were determined by the distribution of holes between the B' and B" orbitals. In summary, controllable fabrication of textured ultra-thin silicon wafers with desired thickness and microstructures could be achieved by one-step, short-time and low-temperature Cu-assisted chemical etching method, exhibiting a great potential use in ultra-thin silicon solar cells. [ABSTRACT FROM AUTHOR]

Sputtered Ge layer was placed between Mo/substrate as a transition layer or between CZTSSe/Mo as a doping layer for CZTSSe/Mo/substrate. The effects of these two Ge layers on the structural, mechanical and photoelectrical properties of CZTSSe thin film and solar cells were studied. It was found that the residual stress of CZTSSe thin film decreased from −2.49 to −0.27 GPa after inserting a Ge transition layer, leading an enhancement in adhesion property. Besides, XPS analysis demonstrated that the diffusion behavior of transitional Ge into CZTSSe absorber through Mo layer during annealing process was nonexistent. The inserted Ge doping layer not only could adjust the band gap of absorber but also improve the band mismatching of CZTSSe/CdS interface. Moreover, the oxidation from Sn4+ to Sn2+ could be suppressed, which could decrease some deep defects in CZTSSe absorber. Ge transition layer and doping layer both made contributions to the increased crystalline quality. After inserting double Ge layers, a relative efficiency enhancement of 48% was achieved due to the reduced residual stress, improved crystalline quality, increased CBO and the alleviated band mismatching of CZTSSe/CdS interface. • Double Ge layers were inserted into flexible CZTSSe thin film solar cells. • The residual stress of absorber was released after inserting a Ge transition layer. • Double Ge layers can alleviate the band mismatching at the interface of CZTSSe/CdS. • The oxidation of Sn+4 to Sn+2 was suppressed after inserting a Ge doping layer. [ABSTRACT FROM AUTHOR]

Flexible Cu(InGa)Se2 (CIGS) solar cells on metallic substrates are highly desirable for versatile energy applications. However, related researches reported on CIGS devices usually used a diffusion barrier, which involves an issue of thermal expansion coefficient matching and complicates the fabrication process. In this study, CIGS solar cells were fabricated on Ni and Ti foils through selenization of metal stacks deposited by e-beam evaporation, without the use of diffusion barrier. The films on Ti foils showed (112) preferred orientation while those on Ni foils exhibited (220) preferred orientation, due to the different crystal orientation of substrates. In–Ni and Ga–Ni phase were observed in films prepared on Ni foils, which led to the existence of Cu2–xSe. As a result, the CIGS solar cells fabricated on Ni foils showed inferior photoelectric properties, whereas those on 50 and 100 μm Ti foils presented conversion efficiency of 4.9% and 6.6%. The discrepancy on efficiency between two cells on Ti foils was ascribed to the different structural properties induced by the thermal stress. After 100 bending cycles, efficiency of cells on 50 and 100 μm thick Ti foils decreased by 1.0% and 2.6% respectively, indicating that CIGS solar cell on 50 μm Ti foil is more promising as flexible device applied on harsh circumstance. [ABSTRACT FROM AUTHOR]

Abstract Silicon solar cells have been center of focus over the decades while the price challenge still hinders its large-scale application. Cost reduction is the urgent pursuit and our work focuses on the texturization process for mono-crystalline silicon. In this report, nanostructures made by metal-assisted chemical etching (MACE) method were introduced before texturization in low-concentration alkaline solution, which shows the advantage in controlling uniformity and thickness losses compared with standard-concentration alkaline solution. By varying MACE etching time, black silicon layers with different morphologies and depths were obtained. Consequently, pyramid structures of different sizes were observed after texturizaiton. Minimum reflectance value of 10.3% and mean pyramid size of 2.95 µm were achieved in low-concentration alkaline solution with optimized MACE etching time. By using SEM, PL and analytical balance to analyze the morphologies of black silicon samples and corresponding thickness losses, we speculated that the nanostructures of black silicon layers acted as the preferential sites for etching, thus accelerated the texturization process and completed within only 10 min. In summary, low-concentration, short-time and less silicon consumption texturization for mono-crystalline silicon could be achieved using our one-step MACE-induced method, exhibiting great potential in commercial photovoltaics utilization and ultra-thin silicon solar cells. [ABSTRACT FROM AUTHOR]

Metal-assisted chemical etching (MACE) method is an efficient way to improve the power conversion efficiency of solar cell by developing nanostructures. Normally, hydrogen peroxide is widely used as an oxidizing agent, through which anisotropic etching of nanostructures could be achieved. Here, nanoscale textured multi-crystalline silicon (mc-Si) solar cell with an efficiency of 18.13% was fabricated by MACE method with potassium permanganate (KMnO4) as an oxidizing agent. The isotropic etching by KMnO4 showed the great uniformity of surface reflectance, corresponding to the isotropic oval pits. The solar cell presented an increase of 0.72mA · cm−2 in the short-circuit current density comparing with the mc-Si solar cell fabricated by the traditional process. Though the efficiency still needed optimizing, isotropic etching for mc-Si would lead a new tendency for MACE technique. [ABSTRACT FROM AUTHOR]

Metal-assisted chemical etching (MACE) method is an efficient way to improve the power conversion efficiency of solar cell by developing nanostructures. Normally, hydrogen peroxide is widely used as an oxidizing agent, through which anisotropic etching of nanostructures could be achieved. Here, nanoscale textured multi-crystalline silicon (mc-Si) solar cell with an efficiency of 18.13% was fabricated by MACE method with potassium permanganate (KMnO4) as an oxidizing agent. The isotropic etching by KMnO4 showed the great uniformity of surface reflectance, corresponding to the isotropic oval pits. The solar cell presented an increase of 0.72mA · cm−2 in the short-circuit current density comparing with the mc-Si solar cell fabricated by the traditional process. Though the efficiency still needed optimizing, isotropic etching for mc-Si would lead a new tendency for MACE technique. [ABSTRACT FROM AUTHOR]

In this paper, we report inverted pyramidal nanostructure based multi-crystalline silicon (mc-Si) solar cells with a high conversion efficiency of 18.62% in large size of 156 × 156 mm 2 wafers. The nanostructures were fabricated by metal assisted chemical etching process followed by a post nano structure rebuilding (NSR) solution treatment. With increasing NSR treatment time, the reflectance and the dimensions of micro oval pits were both influenced. Resulting from both the light trapping ability and passivation efficiency, 500 nm inverted pyramid structure exhibited an ideal solar cell performance. The best solar cell showed a low reflectivity of 3.29% and a 0.91 mA cm −2 increase of short-circuit current density, and its efficiency was 0.45% higher than the acid textured solar cell. This technique presented a great potential to be a standard process for producing highly efficient mc-Si solar cells in the future. [ABSTRACT FROM AUTHOR]

Different thick orthorhombic SnS films were successfully fabricated by sulfurization of various sputtered different thick Sn precursor layers. All the absorption coefficients of different thick SnS films are higher than 2 × 10 cm in the visible light region of 400-800 nm, and the direct band gaps of these SnS films were estimated to be about 1.2 eV. Furthermore, SnS/i-a-Si/n-a-Si solar cells with 205-, 420-, 635-, 845- and 1,060-nm-thick SnS-absorber layers were fabricated, and the 845-nm-thick SnS-absorber-based SnS/i-a-Si/n-a-Si solar cell shows the highest conversion efficiency of 0.42 %, a short-circuit current density of 2.4 mA/cm, and an open-circuit voltage of 362 mV. [ABSTRACT FROM AUTHOR]

In this work, a numerical study has been carried out to investigate the impurity photovoltaic (IPV) effect for silicon solar cells doped with two impurities (indium and thallium). It is found that the conversion efficiency $$\eta $$ of the IPV solar cell doped with two impurities can improve by 2.21 % absolute, which is greater than that of the IPV solar cell doped with indium ( $$\Delta \eta =1.63\,\%$$ ), but less than that of the one doped with thallium ( $$\Delta \eta =2.69\,\%$$ ). It is concluded that introducing two IPV impurities may not be a good selection for implementing the IPV effect since one impurity with poorer IPV effect can absorb some sub-bandgap photons while contributing fewer currents. The location of impurity energy level is critical to the IPV cell performance. For an acceptor-type IPV impurity, the optimized location of the IPV impurity energy level locates at 0.20-0.26 eV above the valence band edge. Our results may help to make better use of the IPV effect for improving solar cell efficiency. [ABSTRACT FROM AUTHOR]

In this paper, large area multi-crystalline silicon (mc-Si) solar cells of 156 mm × 156 mm were fabricated by the combination of Ag-assisted etching and sodium hydroxide (NaOH) treatment. Scanning electron microscope, UV-Vis-NIR spectrophotometer, external quantum efficiency measurement system, and current-voltage test were used to characterize the etched black silicon wafers and the fabricated solar cells. It was found that, though the black mc-Si without NaOH treatment showed a lowest reflectance of 2.03 % in the wavelength of 400-900 nm, the maximum conversion efficiency came from the mc-Si solar cells produced by combination of Ag-assisted etching and NaOH treatment. Though the solar cell with additional NaOH treatment for 30 s presented a reflectance of 5.45 %, it presented the highest conversion efficiency of 18.03 %, which is 0.64 % higher than the traditional mc-Si solar cell (17.39 %) and much higher than that of the black mc-Si solar cell without NaOH treatment (16.24 %). [ABSTRACT FROM AUTHOR]

Abstract: Porous-pyramids structured silicon surface was prepared and its influence on the reflectance of the silicon surface was studied. The porous-pyramids structured surface was prepared by electrochemical etching in HF/C2H5OH solution after texturization in NaOH/IPA solution. The average reflectance of the surface in the range of 400–800nm was as low as 1.9%. The optical photographs and SEM images of the surfaces prepared under optimized condition were investigated. The porous-pyramids structured surface has a gradient-index multilayer structure (i.e., the refraction index of the structure increase from the top to the bottom). A formula that describes the relationship between the reflectance and the index of refraction was used to explain the excellent broadband antireflection of the multilayer silicon surface. The technique of this paper may be valuable in the texturization process for high-efficiency silicon solar cells. [Copyright &y& Elsevier]

Antisite defects induced undesirable open-circuit voltage (Voc) and fill factor (FF) have always been considerable factors that plagued the efficiency enhancement of Cu 2 ZnSn(S,Se) 4 (CZTSSe)-based photovoltaic devices. Accordingly, sputtered Cu–Zn–Sn–S precursor with e-beam evaporated CdS layer on its top and bottom followed by selenization process was firstly proposed to obtain Cd-alloyed flexible CZTSSe thin film solar cells. The introduced CdS significantly improved crystalline quality and promoted grain growth of CZTSSe absorber. Besides, captured conduction band offset (CBO) exhibited a "cliff-like" structure with the maximum value of −0.15 eV when CdS layer was evaporated on top of Cu–Zn–Sn–S precursor, which largely relieved the band alignment issue in CZTSSe/CdS heterojunction. Interestingly, for CZTSSe prepared with CdS on top, Cd element shows a better uniform distribution in absorber than that with CdS on bottom. Finally, thanks to the evaporated CdS layer on precursor top, the efficiency of flexible CZTSSe thin film solar cell was improved from 2.31% to 4.52%, featuring a Voc of 343.53 mV, Jsc of 27.94 mA/cm2 and FF of 47.70%. • Cd-alloyed CZTSSe was obtained by evaporating CdS layer on CZTS precursor. • The evaporated CdS layer largely relieved band mismatching of CZTSSe/CdS. • CBO exhibited a maximum value of −0.15 eV when CdS was on precursor top. • Evaporated CdS on top of precursor can better guarantee the device performance. [ABSTRACT FROM AUTHOR]

In this work, infrared filter property of aluminum doped ZnO (AZO) films prepared on glass substrates with different Ar flow rate by magnetron sputtering was studied. Then Cu was chosen to produce AZO/Cu/AZO sandwich films to further improve its infrared filter property for high transmittance within 380–1100 nm and low transmittance within 1100–2500 nm. The results showed that AZO film had a maximum transmittance over 85% in the region between 380 nm and 1100 nm and a lowest transmittance of 29.70% between 1100 nm and 2500 nm. While AZO/Cu/AZO sandwich film had a maximum transmittance of 80.95% between 380 nm and 1100 nm and its minimum transmittance was 14.61% between 1100 nm and 2500 nm. By using AZO/Cu/AZO sandwich glass as a cover of silicon solar cell, its working temperature showed a less increase of 10.61 °C after 3.5 h under an irradiation of 0.42 sun compared with that where a standard glass was used. This was because that Cu greatly increased the carrier concentration in the sandwich that led to a stronger carrier absorption in infrared wavelength region, so that a reduced thermal effect of the solar cell was obtained. • AZO/Cu/AZO sandwiches films with infrared filter property were prepared. • The effectiveness of the AZO/Cu/AZO sandwich was verified by the FDTD method. • The operating temperature of a solar cell can be reduced over 10°C by AZO/Cu/AZO. • The open circuit voltage of the cell was less reduced by 5.41% using the sandwich. [ABSTRACT FROM AUTHOR]

In this study, a novel strategy for achieving flexible Cd-alloyed Cu 2 ZnSn(S,Se) 4 thin film solar cells is demonstrated by evaporating a CdS layer with different thickness on Cu 2 ZnSnS 4 precursor followed by selenization process. Improved crystalline quality with enlarged grain size was observed through XRD, Raman and SEM measurements. For Cu 2 Cd x Zn 1-x Sn(S,Se) 4 thin film with 50 nm CdS alloying layer, a smallest conduction band offset with −0.20 eV was obtained, which relieved the band mismatching problem between CZTSSe and buffer CdS. Besides, the contact angle of absorber showed a clear difference after Cd alloying, decreasing from 67.8° to 41.2° with the gradual increase in x. Finally, the best device performance benefited from the optimal 50 nm CdS alloying layer, featuring a PCE of 4.01%, Voc of 346.30 mV, Jsc of 24.23 mA/cm−2 and FF of 47.71%, which showed a PCE increase of 1.73% than that without Cd alloying. [ABSTRACT FROM AUTHOR]

The absence of an effective texturing technique for diamond-wire sawn multi-crystalline silicon (DWS mc-Si) solar cells has hindered commercial upgrading from traditional multi-wire slurry sawn silicon (MWSS mc-Si) solar cells. In this work, we present a novel method for the removal of diamond-wire-sawn marks in a multi-crystalline silicon wafer based on metal assisted chemical etching process with Cu/Ag dual elements and nano-structure rebuilding (NSR) treatment to make a uniform inverted pyramid textured structure. The temperature effect of NSR solution was systematically analyzed. It was found that the size of the inverted pyramid structure and the reflectance became larger with the increase of the NSR treatment temperature. Furthermore, the prepared unique inverted pyramid structure not only benefited light trapping, but also effectively removed the saw-marks of the wafer at the same time. The highest efficiency of 19.77% was obtained in solar cells with an inverted pyramid structure (edge length of 600 nm) fabricated by NSR treatment at 50 °C for 360 s, while its average reflectance was 16.50% at a 400–900 nm wavelength range. [ABSTRACT FROM AUTHOR]

• CIGS solar cells were fabricated on ultrathin glass. • Potassium was doped by a simple method during the post-selenization process. • The efficiency of solar cell got enhanced by 2.5% after potassium incorporation. • It was first revealed that K doping retarded the property degradation of solar cell. Flexible Cu(InGa)Se 2 solar cells fabricated on metal foils and plastics have achieved high conversion efficiency so far. However, metal impurities and low temperature tolerance hinder them from further considerable development. Here, 150 μm-thick ultrathin glass with desirable advantages was applied as substrate for Cu(InGa)Se 2 solar cell. Potassium element was doped by a simple method during the post-selenization process. The results showed that the KInSe 2 phase existed in K-doped Cu(InGa)Se 2 films. The K-doped CIGS films were more compact than the pristine one due to the fact that K incorporated in films could form quasi-liquid alkali-metal-Se compounds and improve the compactness of films. K-incorporated CIGS films exhibited enhanced p-type conductivity and different surface energy level. Consequently, K-doped Cu(InGa)Se 2 solar cell achieved an optimal efficiency of 8.3%, which was relatively 43% higher than that of pristine solar cell. Investigation of performance and stability of solar cells manifested that the K incorporation retarded the performance degradation of device during cyclic bending. [ABSTRACT FROM AUTHOR]

• Cd-free CIGS solar cells with a-Si buffer layers are fabricated for the first time. • The conduction band alignment of CIGS/a-Si is a favorable spike. • SCAPS predicts enhanced efficiency by optimization of bandgap and E CB of CIGS films. • The efficiency of cell with modified CIGS film is relatively improved by over 30%. CdS, In 2 S 3 and ZnO-based materials are typically adopted as buffer layers in high efficiency CIGS solar cells. However, the drawbacks involved toxicity, complicated synthesis process and environmental damage of aforementioned materials would someday limit the development themselves. Here, for the first time, eco-friendly and low-cost a-Si thin films prepared by e-beam evaporation were used as buffer layers in CIGS solar cells. Thickness of a-Si films was changed to optimize the performance of CIGS solar cells through investigating their optical, structural and electrical properties. It revealed that the conduction band alignment of CIGS and a-Si is a favorable spike and a 60 nm a-Si film is optimal for CIGS/a-Si interface properties. Following the SCAPS simulation, bandgaps and conduction band energy level of CIGS films were facilely modulated through altering the Ga/(Ga + In) ratios. The conversion efficiency of solar cell with modified CIGS film was relatively improved by over 30% compared to the pristine one. The present work provides a new and eco-friendly strategy for fabrication of CIGS solar cells and expands the application of a-Si thin films as buffer layers for solar cells. [ABSTRACT FROM AUTHOR]

In this paper, we report one bifacial p-type PERC solar cell with efficiency over 22% using laser doped selective emitter produced in larger-scale commercial line on 6-inch mono-crystalline wafer. On front side of the solar cell, square resistance of p-n junction was found to be closely related with laser power at certain laser scan speed and frequency. On the other side, the rear fingers with different ratios of height and width and rear silicon nitride (SiNx) layer with different thickness were optimized, and a highest rear efficiency of the bifacial solar cell was obtained. Finally, bifacial silicon solar cells with the front and rear efficiencies exceeding 22% and 15% (AM1.5, 1000 W/m2, 25 °C) were successfully achieved, respectively. [ABSTRACT FROM AUTHOR]

• Size control of IPs from sub-micro to micro scale was achieved by varying ρ values. • 40 µm random INPs cell achieved 34.8 mA/cm2 current density and 17.44% efficiency. • Superior mechanical performance was proved on INPs based 40 µm c -Si. • Quasi-omnidirectional characteristics of INPs was found between 0° and 60°. • Quasi-omnidirectional performance of INPs was demonstrated by FDTD simulation. Flexible ultrathin c -Si (U-Si) solar cell is widely researched for its potential usage in places with various shapes and sizes. However, light incident angle (θ) varies with positions on the same cell accompanied with the easy crack of cell due to surface textures when the U-Si cell is under bending. Therefore, the fabrication of efficient antireflectance structures with both quasi-omnidirectional performance and superior mechanical performance is greatly required. Here, size control of inverted pyramid (IP) from nano to micro scale as antireflectance structures is realized by altering ρ ([HF]/[HF] + [H 2 O 2 ]) values at room temperature. The IP is obtained through the nanostructure rebuilding (NSR) treatment of Ag assisted chemical etched nanostructures. In comprehensive consideration of optical and mechanical performances, IP-60 (ρ = 60%) textured 40 µm U-Si cell is successfully fabricated with a short-current density of 34.8 mA/cm2 and energy-conversion efficiency of 17.44%, showing an 0.2 mA/cm2 and 0.13% improvement respectively compared with that of the micro pyramids (MP) based one. Moreover, the quasi-omnidirectional characteristics of IP-60 based 40 μm cell over 0–60° is demonstrated by experiment and simulation. The above finding makes it possible to broaden the application scope of U-Si cells into some new areas like stratospheric airships and wearable electronics. [ABSTRACT FROM AUTHOR]

Magnetron co-sputtering method followed by selenization was used for the preparation of Cu2Zn(Sn,Ge)(S,Se)4 (CZTGeSSe) thin film. The impact of Ge doping layer with different sputtering times on crystalline quality, surface roughness, band structure and device performance of CZTGeSSe absorber was systematically investigated. It was found that the increased Ge/(Ge + Sn) ratio could effectively promote the grain growth and improve the band mismatching of CZTGeSSe/CdS interface. The CZTGeSSe thin film with minimum roughness and increased CBO (− 0.54 to − 0.41 eV) was obtained with the increased Ge/(Ge + Sn) ratio of 7.3%. However, oversized grain with rougher surface could result in a non-uniform coverage phenomenon of CdS layer, leading to severe interface recombination. After optimizing the Ge/(Ge + Sn) ratio, the best device performance with an efficiency of 3.19% was achieved in flexible CZTGeSSe thin film solar cells. [ABSTRACT FROM AUTHOR]