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1.
    
In this study, the effect of the Cu concentration on the characteristics of the Cu2ZnSnSe4 (CZTSe) absorber layers and solar cells was systematically analyzed by postselenization of the evaporated precursor deposits. The results demonstrated that an increase in the copper concentration of the precursor linearly increased the Cu content in the final CZTSe thin‐film formation. This significantly increased the particle size and improved the re‐evaporation loss of the SnSe, thus improving the solar cell characteristics. However, a further increase in the Cu concentration reduced the quality of the absorber layer and formed either CuxSe or CTSe secondary phases, which was detrimental to the solar cell characteristics. Here, we introduce a sputtered CdS buffer layer for the CZTSe solar cells. These findings offer new research directions for solving the persistent challenges in the chemical bath deposition (CBD) of the CdS in the CZTSe solar cells.  相似文献   

2.
    
The development of kesterite Cu2ZnSn(S,Se)4 thin‐film solar cells is currently hindered by the large deficit of open‐circuit voltage (Voc), which results from the easy formation of CuZn antisite acceptor defects. Suppressing the formation of CuZn defects, especially near the absorber/buffer interface, is thus critical for the further improvement of kesterite solar cells. In this paper, it is shown that there is a large disparity between the defects in Cu‐ and Ag‐based kesterite semiconductors, i.e., the CuZn or CuCd acceptor defects have high concentration and are the dominant defects in Cu2ZnSn(S,Se)4 or Cu2CdSnS4, but the AgZn acceptor has only a low concentration and the dominant defects are donors in Ag2ZnSnS4. Therefore, the Cu‐based kesterites always show p‐type conductivity, while the Ag‐based kesterites show either intrinsic or weak n‐type conductivity. Based on this defect disparity and calculated band alignment, it is proposed that the Voc limit of the kesterite solar cells can be overcome by alloying Cu2ZnSn(S,Se)4 with Ag2ZnSn(S,Se)4, and the composition‐graded (Cu,Ag)2ZnSn(S,Se)4 alloys should be ideal light‐absorber materials for achieving higher efficiency kesterite solar cells.  相似文献   

3.
    
A soluble graphene, which has a one‐atom thickness and a two‐dimensional structure, is blended with poly(3‐hexylthiophene) (P3HT) and used as the active layer in bulk heterojunction (BHJ) polymer photovoltaic cells. Adding graphene to the P3HT induces a great quenching of the photoluminescence of the P3HT, indicating a strong electron/energy transfer from the P3HT to the graphene. In the photovoltaic devices with an ITO/PEDOT:PSS/P3HT:graphene/LiF/Al structure, the device efficiency increases first and then decreases with the increase in the graphene content. The device containing only 10 wt % of graphene shows the best performance with a power conversion efficiency of 1.1%, an open‐circuit voltage of 0.72 V, a short‐circuit current density of 4.0 mA cm−2, and a fill factor of 0.38 under simulated AM1.5G conditions at 100 mW cm−2 after an annealing treatment at 160 °C for 10 min. The annealing treatment at the appropriate temperature (160 °C, for example) greatly improves the device performance; however, an annealing at overgenerous conditions such as at 210 °C results in a decrease in the device efficiency (0.57%). The morphology investigation shows that better performance can be obtained with a moderate content of graphene, which keeps good dispersion and interconnection. The functionalized graphene, which is cheap, easily prepared, stable, and inert against the ambient conditions, is expected to be a competitive candidate for the acceptor material in organic photovoltaic applications.  相似文献   

4.
    
Quasi-one-dimensional antimony sulfoselenide (Sb2(S,Se)3) semiconductor is one of the most promising light-harvesting materials owing to its simple phase and tunable absorption spectra. However, the oriented [Sb4(S,Se)6]n ribbons of Sb2(S,Se)3 thin films nearly horizontally stacked in parallel to the substrate severely hinders the transport of carriers, yet is critical to control the absorber orientation growth for high-performance Sb2(S,Se)3 solar cells. Herein, a new close spaced sublimated (CSS) CdS buffer layer with high crystallization is introduced for the development of all-vacuum-processed Sb2(S,Se)3 solar cells that attempt to induce the orientation of Sb2(S,Se)3 absorbers to achieve effective carrier transport and reduce the adverse effects. The resulting Sb2(S,Se)3 solar cells with CSS-CdS buffer layers exhibit a prominent [221] orientation and better heterointerfaces as well as lower defect densities and longer capture lifetime compared to the commonly solar cells used chemically deposited CdS buffer layers, as a result of suppressed the non-radiative recombination. The optimized solar cells, yield up to an efficiency of 7.12%, is the first for an all-vacuum-process for Sb2(S,Se)3 solar cells.  相似文献   

5.
    
The charge transport and photogeneration in solar cells based on the low bandgap‐conjugated polymer, poly[2,6‐(4,4‐bis‐(2‐ethylhexyl)‐4H‐cyclopenta[2,1‐b; 3,4‐b′]dithiophene)‐alt‐4,7‐(2,1,3‐benzothiadiazole)] (PCPDTBT) and fullerenes is studied. The efficiency of the solar cells is limited by a relatively low fill factor, which contradicts the observed good and balanced charge transport in these blends. Intensity dependent measurements display a recombination limited photocurrent, characterized by a square root dependence on effective applied voltage, a linear dependence on light intensity and a constant saturation voltage. Numerical simulations show that the origin of the recombination limited photocurrent stems from the short lifetime of the bound electron‐hole pairs at the donor/acceptor interface.  相似文献   

6.
    
Flexible and stretchable organic solar cells (OSCs) have attracted enormous attention due to their potential applications in wearable and portable devices. To achieve flexibility and stretchability, many efforts have been made with regard to mechanically robust electrodes, interface layers, and photoactive semiconductors. This has greatly improved the performance of the devices. State‐of‐the‐art flexible and stretchable OSCs have achieved a power conversion efficiency of 15.21% (16.55% for tandem flexible devices) and 13%, respectively. Here, the recent progress of flexible and stretchable OSCs in terms of their components and processing methods are summarized and discussed. The future challenges and perspectives for flexible and stretchable OSCs are also presented.  相似文献   

7.
    
A new class of low‐bandgap copolymers based on benzodithiophene (BDT) and thieno[3,4‐c]pyrrole‐4,6‐dione (TPD) units is reported. Chemical modifications of the conjugated backbone promote both high molecular weights and processability while allowing for tuning of the electronic properties. Copolymers with substituted thiophene spacers (alkyl chains facing the BDT unit) or unsubstituted thiophene spacers tend to have low power conversion efficiencies (PCE less than 1%) due to a bad morphology of the active layer, whereas copolymers with substituted thiophene spacers (alkyl chains facing TPD unit) show enhanced morphology and PCEs up to of 3.9%. Finally, BDT‐TPD copolymers without any thiophene spacers still show the best performances with power conversion efficiencies up to 5.2%.  相似文献   

8.
    
Abundant intrinsic defects and defect clusters in Cu2ZnSn(S,Se)4 (CZTSSe) solar cells lead to severe nonradiative recombination and limited photoelectric performance. Therefore, developing effective method to suppress the detrimental defects is the key to achieve high-efficiency solar cell. Herein, a convenient two-step cooling strategy in selenization process is reported to suppress the CuZn and SnZn defects and defect clusters synergistically. The results show that rapid cooling during section from selenization temperature to turning temperature can inhibit the volatilization of Sn and restrain the corresponding Sn-related defects, while slow cooling during the subsequent temperature section can reduce the degree of Cu-Zn disorder. Benefitting from the synergistic effect of two-step cooling, a significantly lowered concentration of SnZn and CuZn defect and their defect clusters [2CuZn+SnZn] in absorber is observed, meanwhile, a reduced band tailing effect and promoted carrier collection efficiency of the photovoltaic device is obtained. Finally, a device with improved open-circuit voltage (Voc) of 505.5 mV and efficiency of 12.87% is achieved. This study demonstrates the impact of cooling process on defects controlling for the first time and provides a simple and effective new strategy for intrinsic defect control, which may be universal in other inorganic thin film solar cells.  相似文献   

9.
    
One of the main issues that limits the efficiency of kesterite solar cells is the low diffusion and chemical activity of selenium clusters. Here, this work proposes a simple and effective pre-selenization strategy using Na2(Se2S) solution, which enables the direct introduction of hyperactive Se2, Se3, and Se4 into the precursors. The results demonstrate that Se2, Se3, and Se4 promote the formation of the Cu2-xSe liquid phase and enhance the diffusion of elements from different micro-regions. Consequently, the ratios of Cu/(Zn + Sn) and Sn/Zn in different micro-regions of the absorber are controlled within the optimal range, exhibiting reduced fluctuations. The controlled environment suppresses the formation of CuZn and SnZn defects, as well as [2CuZn + SnZn] defect clusters. Finally, a power conversion efficiency (PCE) of 12.86% is achieved, which is the highest PCE for kesterite solar cells made under ambient pressure and with N,N-dimethylformamide solvent.  相似文献   

10.
    
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11.
    
Valuation of photovoltaic devices depends strongly on the measured power output of the device. This quantity is usually determined under artificial sunlight in production line measurement systems or industrial or research test labs. A practical calibration chain is realized essentially with measurements at solar simulators. The measurement conditions are defined in the IEC 60904 series of standards. An important part of the standard testing conditions is the definition of a specific spectral distribution of the sunlight (AM1.5 global). The inevitable deviations of the spectrum of artificial light sources from the standard spectrum have to be taken into account by a spectral mismatch factor. The uncertainty of this crucial correction is spectrally dependent, in most cases unknown and complex and inconvenient to evaluate. In this article a randomizing method is proposed which allows one to calculate the uncertainty of the mismatch factor from the uncertainties of the input parameters determined with high spectral resolution. Based on a range of different spectral responses of solar cells on the one hand and variations of the solar simulator spectral distribution on the other, we are able to generalize the results to a broad set of measurement configurations. A sensitivity analysis reveals the crucial wavelength regions and thus allows the systematic optimization of simulator spectra and selection of reference cells. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

12.
    
A series of novel acceptor–donor–acceptor oligothiophenes terminally substituted with the 1‐(1,1‐dicyanomethylene)‐cyclohex‐2‐ene (DCC) acceptor has been synthesized. Structural, thermal, optoelectronic, and photovoltaic properties of the π‐extended DCCnTs (n = 1–4) are characterized and contrasted to the trends found for the series of parent dicyanovinyl (DCV)‐substituted oligothiophenes DCVnT. The optoelectronic properties reveal the influence of the additional exocyclic, sterically fixed double bonds in trans‐configuration in the novel DCCnT derivatives. A close correspondence for derivatives with equal number of double bonds, that is, DCCnTs and DCV(n + 1)Ts, is identified. Despite having the same energy gap, the energy levels of the frontier orbitals, HOMO and LUMO, for the DCC ‐ derivatives are raised and more destabilized due to the aromatization energy of a thiophene ring versus two exocyclic double bonds indicating improved donor and reduced acceptor strength. DCC‐terthiophenes give good photovoltaic performance as donor materials in vacuum‐processed solar cells (power conversion efficiencies ≤ 4.4%) clearly outperforming all comparable DCV4T derivatives.  相似文献   

13.
    
The microstructures of photo‐ and counter‐electrodes play critical roles in the performance of dye‐sensitized solar cells (DSSCs). In particular, various interfaces, such as fluorinated‐tin oxide (FTO)/TiO2, TiO2/TiO2, and TiO2/electrolyte, in DSSCs significantly affect the final power conversion efficiency (PCE). However, research has generally focused more on the design of various nanostructured semiconducting materials with emphasis on optimizing chemical or/and physical properties, and less on these interface functionalizations for performance improvement. This work explores a new application of graphene to modify the interface of FTO/TiO2 to suppress charge recombination. In combination with interfaces functionalization of TiO2/TiO2 for low charge‐transport resistance and high charge‐transfer rate, the final PCE of DSSC is remarkably improved from 5.80% to 8.13%, achieving the highest efficiency in comparison to reported graphene/TiO2‐based DSSCs. The method of using graphene to functionalize the surface of FTO substrate provides a better alternative method to the conventional pre‐treatment through hydrolyzing TiCl4 and an approach to reduce the adverse effect of microstructural defect of conducting glass substrate for electronic devices.  相似文献   

14.
    
In the present work, we correlate the photophysical and photovoltaic properties with the respective film morphologies of three different blends made of the fluorene copolymers poly(9,9′‐dioctylfluorene‐co‐benzothiadiazole) (F8BT), poly[9,9′‐dioctylfluorene‐co‐N‐(4‐butylphenyl)diphenylamine] (TFB), and poly[9,9′‐dioctyfluorene‐co‐bis‐N,N′‐(4‐butylphenyl)‐bis‐N,N‐phenyl‐1,4‐phenylenediamine] (PFB) when blended with a perylene tetracarboxylic diimide (PDI) derivative. Additional photophysical studies in reference PDI blends of the electronically inert poly(styrene) matrix address the enhanced PDI intermolecular solid‐state interactions. We resolve the process of resonance energy transfer from excited polymer hosts to PDI and the process of photoinduced hole transfer from PDI to the polymer hosts. We deduce the efficiency of charge‐transfer PDI photoluminescence (PL) quenching and we discuss the power‐law PL kinetics seen in the as‐spun systems. Next we determine the dependence of the device external quantum efficiency (EQE) of these blends, in a range of annealing temperatures and PDI loadings. Differential scanning calorimetry enables precise selection of annealing temperatures. Optical microscopy shows that annealing enhances the order characteristics in the PDI aggregates in the F8BT:PDI system. In the case of the TFB:PDI and PFB:PDI blends, AFM studies suggest the formation of PDI‐rich domains on the film/air interface. The degree of order in the π–π stacking of the PDI monomers is inferred by the UV–Vis and PL spectra of the blends. The extent of order characteristics in PDI aggregates is correlated with the thermal properties of the hosts that control PDI molecular mobility upon annealing. The efficient dispersion of disrupted PDI crystallites is proposed to form appropriate percolation networks that favor balanced extraction of photogenerated carriers.  相似文献   

15.
    
The hysteresis in perovskites devices puzzled researchers because it was a big hurdle for device stability and the origin of it was still a riddle for people to solve. Here we reported our analysis in mechanism of the hysteresis based on the trap states in the perovskites film surface. We tried to explain the current hysteresis through the dynamic charge trapping–detrapping processes and the conclusion applied both in porous and planar structure devices. However, the proportion of deep traps and shallow traps are different in planar structure device and in porous structure device. Furthermore, we found perovskite devices has potentials of serving as memory devices due to the photocurrent hysteresis. The on/off ratio of memory based on perovskite can be higher than 60 and the write time was as low as 0.54 s as memory. It also had a very low read bias near 0 V. Moreover, the devices show multi-bit property and a multi-bit organic memory came forward as a novel application of perovskite devices.  相似文献   

16.
曹璐  李梦轲  魏强  张威 《微纳电子技术》2007,44(11):985-988,1003
用低压化学气相沉积法制备了T形和V形纳/微米ZnO同质结,用扫描电子显微镜(SEM)和高倍光学成像显微镜观察了同质结的结构与生长形貌,分析了其结构及生长机理。利用ZnO同质结组装成了纳/微米ZnO同质结器件,分析研究了这些器件的I-V特性,并对I-V特性变化规律进行了分析讨论。  相似文献   

17.
    
Semiconductor nanocrystals are promising materials for printed optoelectronic devices, but their high surface areas are susceptible to forming defects that hinder charge carrier transport. Furthermore, correlation of chalcogenide nanocrystal (NC) material properties with solar cell operation is not straightforward due to the disorder often induced into NC films during processing. Here, an improvement in long‐range ordering of PbSe NCs symmetry that results from halide surface passivation is described, and the effects on chemical, optical, and photovoltaic device properties are investigated. Notably, this passivation method leads to a nanometer‐scale rearrangement of PbSe NCs during ligand exchange, improving the long‐range ordering of nanocrystal symmetry entirely with inorganic surface chemistry. Solar cells constructed with a variety of architectures show varying improvement and suggest that triplet formation and ionization, rather than carrier transport, is the limiting factor in singlet fission solar cells. Compared to existing protocols, our synthesis leads to PbSe nanocrystals with surface‐bound chloride ions, reduced sub‐bandgap absorption and robust materials and devices that retain performance characteristics many hours longer than their unpassivated counterparts.  相似文献   

18.
    
The reduction of carbon dioxide (CO2) into chemical feedstock is drawing increasing attention as a prominent method of recycling atmospheric CO2. Although many studies have been devoted in designing an efficient catalyst for CO2 conversion with noble metals, low selectivity and high energy input still remain major hurdles. One possible solution is to use the combination of an earth‐abundant electrocatalyst with a photoelectrode powered by solar energy. Herein, for the first time, a p‐type silicon nanowire with nitrogen‐doped graphene quantum sheets (N‐GQSs) as heterogeneous electrocatalyst for selective CO production is demonstrated. The photoreduction of CO2 into CO is achieved at a potential of ?1.53 V versus Ag/Ag+, providing 0.15 mA cm?2 of current density, which is 130 mV higher than that of a p‐type Si nanowire decorated with well‐known Cu catalyst. The faradaic efficiency for CO is 95%, demonstrating significantly improved selectivity compared with that of bare planar Si. The density functional theory (DFT) calculations are performed, which suggest that pyridinic N acts as the active site and band alignment can be achieved for N‐GQSs larger than 3 nm. The demonstrated high efficiency of the catalytic system provides new insights for the development of nonprecious, environmentally benign CO2 utilization.  相似文献   

19.
    
We report the effect of COOH-functionalized single walled carbon nanotubes(COOH-SWCNT) on the electrical and photovoltaic characteristics of Malachite Green(MG) dye based photovoltaic cells. Two different types of photovoltaic cells were prepared, one with MG dye and another by incorporating COOH-SWCNT with this dye. Cells were characterized through different electrical and photovoltaic measurements including photocurrent measurements with pulsed radiation. From the dark current–voltage(I–V) characteristic results, we observed a certain transition voltage(Vth/ for both the cells beyond which the conduction mechanism of the cells change sharply. For the MG dye, Vthis 3.9 V whereas for COOH-SWCNT mixed with this dye, Vthdrops to 2.7 V. The device performance improves due to the incorporation of COOH-SWCNT. The open circuit voltage and short circuit current density change from 4.2 to 97 m V and from 108 to 965 A/cm2 respectively. Observations from photocurrent measurements show that the rate of growth and decay of the photocurrent are quite faster in the presence of COOH-SWCNT. This observation indicates a faster charge separation processes due to the incorporation of COOHSWCNT in the MG dye cells. The high aspect ratio of COOH-SWCNT allows efficient conduction pathways for the generated charge carriers.  相似文献   

20.
    
A series of low‐bandgap alternating copolymers of dithienosilole and thienopyrrolodione (PDTSTPDs) are prepared to investigate the effects of the polymer molecular weight and the alkyl chain length of the thienopyrrole‐4,6‐dione (TPD) unit on the photovoltaic performance. High‐molecular‐weight PDTSTPD leads to a higher hole mobility, lower device series resistance, a larger fill factor, and a higher photocurrent in PDTSTPD:[6,6]‐phenyl C71 butyric acid methyl ester (PC71BM) bulk‐heterojunction solar cells. Different side‐chain lengths show a significant impact on the interchain packing between polymers and affect the blend film morphology due to different solubilities. A high power conversion efficiency of 7.5% is achieved for a solar cell with a 1.0 cm2 active area, along with a maximum external quantum efficiency (EQE) of 63% in the red region.  相似文献   

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