Panchromatic photon-harvesting by hole-conducting materials in inorganic-organic heterojunction sensitized-solar cell through the formation of nanostructured electron channels

Additional photon-harvesting by hole transporting materials in Sb(2)S(3)-sensitized solar cell is demonstrated through the formation of electron channels in the hole transporter such as P3HT (poly(3-hexylthiophene)) and PCPDTBT(poly(2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7(2,1,3-benzothiadiazole)) that can act as both a hole conductor and light absorber. As a result, the short-circuit current density is improved with an increment in overall efficiency. These findings provide new insights into use of light-absorbing conjugated polymers as a hole conductor in the inorganic-organic heterojunction sensitized solar cells.     

Enhancing photovoltaic performance of photoelectrochemical solar cells with nano-sized ultra thin Sb2S3-sensitized layers in photoactive electrodes

Sb₂S₃-sensitized photoelectrochemical solar cells were prepared with photoactive electrodes containing thick and thin Sb₂S₃-sensitized layers, polyaniline hole conductor containing little amount of de-ionized water, and Pt counter electrodes. The device with the thin Sb₂S₃-sensitized layer shows much higher power conversion efficiency (3.78 %) than that of the device with the thick Sb₂S₃-sensitized layer (0.88 %). The FESEM and TEM images reveal that the device with the thin Sb₂S₃-sensitized layer is nanostructure, as that of the traditional quantum dot sensitized solar cell, while the device with the thick Sb₂S₃-sensitized layer is flat configuration. The photoactive electrode with the thin Sb₂S₃-sensitized layer shows higher light absorption, lower charge transfer resistance and longer electron lifetime compared with that of the one with the thick Sb₂S₃-sensitized layer, which results in higher photocurrent generation of the device.     

新型Sb2S3-Sb2Se3与单晶二氧化钛纳米阵列复合结构在太阳能电池领域的应用

近年来,半导体量子点敏化太阳能电池作为新一代的太阳能电池,引起了广泛的关注．Sb2S2和Sb2Se3量子点由于具有出色的光吸收特性与带隙的可调控性,已成为敏化太阳能电池领域的重要组成部分．通过水热法,二氧化钛（TiO2）单晶纳米阵列被成功生长在FTO导电玻璃上．通过连续离子层吸附法（SILAR）,Sb2S3Sb2Se3复合纳米结构被生长在二氧化钛单晶纳米阵列的表面．利用x射线衍射（XRD）表征Sb2S3和Sb2Se3纳米晶体的晶相,利用扫描电子显微镜（SEM）表征其形貌,发现在这一复合结构中,二氧化钛单晶纳米阵列与Sb2S3结合之后所留下的空隙被Sb2Se3量子点填充,从而提高了结构表面积的利用率．随着连续离子层吸附法反应周期的增加,Sb2S3-Sb2Se3,与二氧化钛单晶纳米阵列共同形成复合结构的带隙发生了明显的红移,吸收边在可调控的情况下由1．7eV向红外波段发生了移动．这种纳米结构的比表面积大、工艺简单、结构致密、沉积速率快、可调控性强,对于今后敏化太阳能电池领域的应用有很大的启发作用．     

Nanoscale ferroelectric and piezoelectric properties of Sb2S3 nanowire arrays

We report the first observation of piezoelectricity and ferroelectricity in individual Sb(2)S(3) nanowires embedded in anodic alumina templates. Switching spectroscopy-piezoresponse force microscopy (SS-PFM) measurements demonstrate that individual, c-axis-oriented Sb(2)S(3) nanowires exhibit ferroelectric as well as piezoelectric switching behavior. Sb(2)S(3) nanowires with nominal diameters of 200 and 100 nm showed d(33(eff)) values around 2 pm V(-1), while the piezo coefficient obtained for 50 nm diameter nanowires was relatively low at around 0.8 pm V(-1). A spontaneous polarization (P(s)) of approximately 1.8 μC cm(-2) was observed in the 200 and 100 nm Sb(2)S(3) nanowires, which is a 100% enhancement when compared to bulk Sb(2)S(3) and is probably due to the defect-free, single-crystalline nature of the nanowires synthesized. The 180° ferroelectric monodomains observed in Sb(2)S(3) nanowires were due to uniform polarization alignment along the polar c-axis.     

Wet chemical synthesis and self-assembly of SnS2 nanoparticles on TiO2 for quantum dot-sensitized solar cells

SnS2 nanoparticles were synthesized through a simple wet chemical process at room temperature. The SnS2 nanoparticles were approximately spherical in shape and had diameter about 3-4 nm. SnS2-sensitized TiO2 electrodes were fabricated by the immersion of chemically modified TiO2 to well-dispersed SnS2 solution for 72 h (i.e., self-assembly method.) SnS2-sensitized TiO2 electrodes were applied in quantum dot-sensitized solar cells (QDSSCs). Under AM1.5 irradiation with 100 mW/cm2 light intensity (at 1 sun), the short-circuit current density (J(sc)), the open-circuit voltage (V(oc)), the fill factor (FF), and the energy conversion efficiency (eta) were 0.47 mA/cm2, 0.29 V, 0.58 and 0.081%, respectively.     

High-efficiency solid-state dye-sensitized solar cells based on TiO(2)-coated ZnO nanowire arrays

Replacing the liquid electrolytes in dye-sensitized solar cells (DSCs) with solid-state hole-transporting materials (HTMs) may solve the packaging challenge and improve the long-term stability of DSCs. The efficiencies of such solid-state DSCs (ss-DSCs), however, have been far below the efficiencies of their counterparts that use liquid electrolytes, primarily due to the challenges in filling HTMs into thick enough sensitized films based on sintered TiO(2) nanoparticles. Here we report fabrication of high-efficiency ss-DSCs using multilayer TiO(2)-coated ZnO nanowire arrays as the photoanodes. The straight channel between the vertically aligned nanostructures combined with a newly developed multistep HTM filling process allows us to effectively fill sensitized films as thick as 50 μm with the HTMs. The resulting ss-DSCs yield an average power conversion efficiency of 5.65%.     

Symmetry-Breaking Induced Dipole Enhancement for Efficient Spiro-Type Hole Transporting Materials: Easy Synthesis with High Stability

Spiral cores are crucial for designing efficient hole transporting materials (HTMs) for perovskite solar cells (PSCs), owing to their no-planar 3D architecture, high thermal stability, good solubility, and beneficial solid-state morphology. A lack of facile synthetic procedures for the spiral core limited the development of novel and stable spiral HTMs. In this regard, a one-step reaction is adopted to produce several novel acceptor-embedded spiral cores containing electron-withdrawing carbonyl group embedded orthogonal spiral conformation. After coupling with triphenylamine donors, symmetry-breaking spiral HTMs with uneven charge distribution can be obtained, bearing the advantages of adjustable dipole moment and enhanced structural stability. A combined theoretical and experimental study shows that the HTM with a stronger dipole moment can easily adsorb on the surface of perovskite via electrostatic potential, and the closer distance promoted facile hole transfer from perovskite to HTMs. In the end, PSCs based on strongly polarized spiro-BC-OMe achieved efficient hole extraction and thus an improved fill factor, promoting a power conversion efficiency (PCE) of 22.15%, and a module-based PCE of 18.61% with an active area of 16.38 cm². This study provides a new avenue for designing HTMs with strong dipole moments for efficient PSCs.     

Increasing open circuit voltage by adjusting work function of hole-transporting materials in perovskite solar cells

A series of conductive polymers, i.e., poly(3-methylthiophene) (PMT), poly(thiophene) (PT), poly(3-bromothiophene) (PBT) and poly(3-chlorothiophene) (PCT), were prepared via the electrochemical polymerization process. Subsequently, their application as hole-transporting materials (HTMs) in CH₃NH₃PbI₃ perovskite solar cells was explored. It was found that rationally increasing the work function of HTMs proves beneficial in improving the open circuit voltage (V _oc) of the devices with an ITO/conductive-polymer/CH₃NH₃PbI₃/C₆₀/BCP/Ag structure. In addition, the higher-V _oc devices with a higher-work-function HTM exhibited higher recombination resistances. The highest open circuit voltage of 1.04 V was obtained from devices with PCT, with a work function of–5.4 eV, as the hole-transporting layer. Its power conversion efficiency attained a value of approximately 16.5%, with a high fill factor of 0.764, an appreciable open voltage of 1.01 V and a short circuit current density of 21.4 mA·cm^–2. This simple, controllable and low-cost manner of preparing HTMs will be beneficial to the production of large-area perovskite solar cells with a hole-transporting layer.

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Graphene nanoplatelets outperforming platinum as the electrocatalyst in co-bipyridine-mediated dye-sensitized solar cells

Graphene nanoplatelets (GNP) in the form of thin semitransparent films on F-doped SnO2 (FTO) exhibit high electrocatalytic activity for the Co(bpy)3(3+/2+) redox couple in acetonitrile electrolyte solution. The GNP film is superior to the traditional electrocatalyst, that is, platinum, both in charge-transfer resistance (exchange current) and in electrochemical stability under prolonged potential cycling. The good electrochemical performance of GNP is readily applicable for dye-sensitized solar cells with Y123-sensitized TiO2 photoanodes and Co(bpy)3(3+/2+) as the redox shuttle. The dye-sensitized solar cell with GNP cathode is superior to that with the Pt-FTO cathode particularly in fill factor and in power conversion efficiency at higher illumination intensity.     

Electron transfer properties of organic dye-sensitized solar cells based on indoline sensitizers with ZnO nanoparticles

Two indoline dyes, coded D149 and D205, were used as the sensitizers of ZnO dye-sensitized solar cells (DSCs) with optimal energy conversion efficiencies of more than 5%, under AM 1.5 full sunlight illumination (100?mW?cm( - 2)). Higher interfacial charge transfer rate and retardant fluorescence decay confirmed from transient fluorescence illustrated that D205-sensitized ZnO DSCs could possess better electron transport than D149-sensitized ZnO DSCs. The enhancement of V(oc) and J(sc) for D205-sensitized ZnO DSCs was ascribed to the effective suppression of electron recombination by extending the alkyl chain on the terminal rhodanine moiety from ethyl to octyl. The evidence of enhanced electron diffusion coefficient was further shown by electrochemical impedance spectroscopy (EIS).     

Highly π-extended copolymer as additive-free hole-transport material for perovskite solar cells

Organolead halide perovskite solar cells have achieved a certified power-conversion efficiency (PCE) of 22.1% and are thus among the most promising candidates for next-generation photovoltaic devices. To date, most high-efficiency perovskite solar cells have employed arylamine-based hole-transport materials (HTMs), which are expensive and have a low mobility. The complicated doping procedures and the potentially stability-adverse dopants used in these HTMs are among the major bottlenecks for the commercialization of perovskite solar cells (PSCs). Herein, we present a polythiophene-based copolymer (PDVT-10) with a hole mobility up to 8.2 cm²·V^?1·s^?1 and a highest occupied molecular orbital level of ?5.28 eV as a hole-transport layer (HTL) for a PSC. A device based on this new HTM exhibited a high PCE of 13.4% under 100 mW·cm^?2 illumination, which is one of the highest PCEs reported for the dopant-free polymer-based HTLs. Moreover, PDVT-10 exhibited good solution processability, decent air stability, and thermal stability, making it a promising candidate as an HTM for PSCs.

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Dopant‐Free Small‐Molecule Hole‐Transporting Material for Inverted Perovskite Solar Cells with Efficiency Exceeding 21%

Hole‐transporting materials (HTMs) play a critical role in realizing efficient and stable perovskite solar cells (PVSCs). Considering their capability of enabling PVSCs with good device reproducibility and long‐term stability, high‐performance dopant‐free small‐molecule HTMs (SM‐HTMs) are greatly desired. However, such dopant‐free SM‐HTMs are highly elusive, limiting the current record efficiencies of inverted PVSCs to around 19%. Here, two novel donor–acceptor‐type SM‐HTMs (MPA‐BTI and MPA‐BTTI) are devised, which synergistically integrate several design principles for high‐performance HTMs, and exhibit comparable optoelectronic properties but distinct molecular configuration and film properties. Consequently, the dopant‐free MPA‐BTTI‐based inverted PVSCs achieve a remarkable efficiency of 21.17% with negligible hysteresis and superior thermal stability and long‐term stability under illumination, which breaks the long‐time standing bottleneck in the development of dopant‐free SM‐HTMs for highly efficient inverted PVSCs. Such a breakthrough is attributed to the well‐aligned energy levels, appropriate hole mobility, and most importantly, the excellent film morphology of the MPA‐BTTI. The results underscore the effectiveness of the design tactics, providing a new avenue for developing high‐performance dopant‐free SM‐HTMs in PVSCs.     

Intensive Exposure of Functional Rings of a Polymeric Hole‐Transporting Material Enables Efficient Perovskite Solar Cells

A variety of dopant‐free hole‐transporting materials (HTMs) is effectively applied in perovskite solar cells (PSCs); however, HTMs with the additional function of HTM/perovskite interfacial optimization that is crucial to their photovoltaic performance are really limited. In this work, the design of an HTM bearing an intensive exposure of its functional aromatic rings to perovskite layer via side‐chain engineering is attempted. With an edge‐on orientation and a short distance to perovskite, this HTM was expected to display an excellent ability to extract holes from and passivate defects in the perovskite layer. To demonstrate this strategy, an alternating copolymer was constructed with a 2,5‐di‐2‐ethylhexyloxy‐1,4‐phenylene unit and a bithiophene unit, and the PSC based on this polymer showed an ultrahigh short‐circuit current density of 25.50 mA cm^?2, which was the highest so far presented by dopant‐free organic HTMs. A comparable power conversion efficiency of 19.68% (certified: 19.5%) to that of a control 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene (spiro‐OMeTAD) device (19.81%) was thus obtained, which is the highest value ever reported for mesoporous PSCs based on dopant‐free polymeric HTMs.     

CuGaSe2 solar cells using atomic layer deposited Zn(O,S) and (Zn,Mg)O buffer layers

The band gap of Zn(O,S) and (Zn,Mg)O buffer layers are varied with the objective of changing the conduction band alignment at the buffer layer/CuGaSe₂ interface. To achieve this, alternative buffer layers are deposited using atomic layer deposition. The optimal compositions for CuGaSe₂ solar cells are found to be close to the same for (Zn,Mg)O and the same for Zn(O,S) as in the CuIn_0.7Ga_0.3Se₂ solar cell case. At the optimal compositions the solar cell conversion efficiency for (Zn,Mg)O buffer layers is 6.2% and for Zn(O,S) buffer layers it is 3.9% compared to the CdS reference cells which have 5-8% efficiency.     

锑掺杂氧化锡薄膜的制备及其对硅基太阳能电池工作温度的影响

硅基太阳能电池占据着光伏发电的最大份额, 但是在阳光下其工作温度过高会降低电池效率和功率输出, 因此降低硅基太阳能电池在阳光下的工作温度具有重要意义。本研究以氯化亚锡和三氯化锑为原料, 通过简单的溶胶-凝胶法制备锑掺杂氧化锡(ATO)薄膜, 将其作为硅电池盖板, 研究了锑(Sb)掺杂量和薄膜厚度对薄膜红外阻隔性能和硅电池降温性能的影响。研究表明, ATO薄膜的红外遮蔽性能随薄膜厚度增加而提高, 但可见光透过率随之降低。用AM1.5太阳光持续照射30 min后, 使用旋涂1~4层ATO薄膜盖板的硅电池温度比使用普通玻璃盖板的电池最大降低2.7 ℃, 晶硅电池效率可以保持在10.79%以上。此外, 使用10mol%锑掺杂的3层ATO薄膜盖板的硅电池在连续光照30 min后, 温度比使用普通玻璃盖板最大降低1.5 ℃, 效率提高了0.43%。     

Synthesis of various morphologies of Sb2S3 based on amorphous-crystalline transition with related photodegradation

Journal of Materials Science - In this paper, two morphologies of crystalline Sb2S3 as dumbbell-like Sb2S3 and bundle-like Sb2S3 were synthesized by different phase-transformation of...     

TiO2 nanorod arrays functionalized with In2S3 shell layer by a low-cost route for solar energy conversion

We report the fabrication and characterization of a TiO(2)-In(2)S(3) core-shell nanorod array structure for application of semiconductor-sensitized solar cells. Hydrothermally synthesized TiO(2) nanorod arrays on FTO glass substrates are functionalized with a uniform In(2)S(3) shell layer by using the successive ion layer adsorption and reaction (SILAR) method. This low-cost technique promotes a uniform deposition of In(2)S(3) nanoshells on the surface of TiO(2) nanorods, thus forming an intact interface between the In(2)S(3) shell and TiO(2) core. Results show that the thickness of In(2)S(3) shell layers as well as the visible light absorption threshold can be effectively controlled by varying the coating cycles during the SILAR process. The best reproducible performance of the sandwich solar cell using the TiO(2)-In(2)S(3) core-shell nanorod arrays as photoelectrodes was obtained after 30 SILAR cycles, exhibiting a short-circuit current (I(sc)) of 2.40 mA cm(-2), an open-circuit voltage (V(oc)) of 0.56 V, a fill factor (ff) of 0.40 and a conversion efficiency (η) of 0.54%, respectively. These results demonstrate a feasible and controllable route towards In(2)S(3) coating on a highly structured substrate and a proof of concept that such TiO(2)-In(2)S(3) core-shell architectures are novel and promising photoelectrodes in nanostructured solar cells.     

Sb<Subscript>2</Subscript>Se<Subscript>3</Subscript> solar cells prepared with selenized dc-sputtered metallic precursors

Sb₂Se₃ with suitable bandgap and non-toxic, abundant composition represents a promising absorber material as a replacement for Cu₂ZnSnS₄ and Cu(In,Ga)Se₂ for thin film solar cells. In this paper, we investigated the effect of annealing temperature on selenizing metal precursor deposited by sputtering. With optimized temperature, the best performance of the devices achieved the efficiency of 0.72 % with an open circuit voltage of 368 mV. This study provide the guideline to fabricate Sb2Se3 thin film solar cell as the same structure as CIGS.     

Highly Efficient p‐i‐n Perovskite Solar Cells Utilizing Novel Low‐Temperature Solution‐Processed Hole Transport Materials with Linear π‐Conjugated Structure

Alternative low‐temperature solution‐processed hole‐transporting materials (HTMs) without dopant are critical for highly efficient perovskite solar cells (PSCs). Here, two novel small molecule HTMs with linear π‐conjugated structure, 4,4′‐bis(4‐(di‐p‐toyl)aminostyryl)biphenyl (TPASBP) and 1,4′‐bis(4‐(di‐p‐toyl)aminostyryl)benzene (TPASB), are applied as hole‐transporting layer (HTL) by low‐temperature (sub‐100 °C) solution‐processed method in p‐i‐n PSCs. Compared with standard poly(3,4‐ethylenedioxythiophene): poly(styrenesulfonic acid) (PEDOT:PSS) HTL, both TPASBP and TPASB HTLs can promote the growth of perovskite (CH₃NH₃PbI₃) film consisting of large grains and less grain boundaries. Furthermore, the hole extraction at HTL/CH₃NH₃PbI₃ interface and the hole transport in HTL are also more efficient under the conditions of using TPASBP or TPASB as HTL. Hence, the photovoltaic performance of the PSCs is dramatically enhanced, leading to the high efficiencies of 17.4% and 17.6% for the PSCs using TPASBP and TPASB as HTL, respectively, which are ≈40% higher than that of the standard PSC using PEDOT:PSS HTL.     

Influences of solvents on morphology,light absorbing ability and photovoltaic performance of Sb2S3-sensitized TiO2 photoanodes by chemical bath deposition method

Sb₂S₃-sensitized TiO₂ films were prepared with chemical bath deposition (CBD) method. The influences of acetone and acetic acid solvents on the morphologies of Sb₂S₃-sensitized TiO₂ films and their light absorbing ability were investigated. Furthermore, photoelectrochemical solar cells containing Sb₂S₃-sensitized TiO₂ photoanodes, polyaniline, and Pt counter electrodes were prepared to investigate the photovoltaic performance of these Sb₂S₃-sensitized TiO₂ films. It was found that the Sb₂S₃-sensitized TiO₂ photoanode prepared with CBD method in the solution containing acetic acid showed higher light absorption in short-wavelength region, lower charge transfer resistance and longer electron lifetime compared with that of the one prepared with CBD method in the solution containing acetone, resulting in better photovoltaic performance.