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Luminescent europium-doped titania for efficiency and UV-stability enhancement of planar perovskite solar cells
摘要： Perovskite solar cells (PSCs) have demonstrated high power conversion efficiencies (PCEs) but poor stability against ultraviolet (UV) irradiation. Here, we report a one-pot synthesized luminescent europium-doped titania (Eu-TiO2) via chemical-bath deposition at low-temperature (70 oC) for planar PSCs, which enables simultaneous efficiency and UV-stability enhancement. We show that the Eu-TiO2 could effectively convert damaging UV photons into useful visible luminescence for additional light harvesting. A more optimal energy band alignment at the Eu-TiO2/perovskite interface leads to facilitated charge extraction and suppressed non-radiative recombination. The use of Eu-TiO2 in PSCs results in increased photocurrent and open-circuit voltage, yielding an enhanced PCE of 21.40% with relative to pristine TiO2 device (19.22%). More importantly, the Eu-TiO2 devices exhibit remarkably improved UV stability, retaining 75% of the initial PCE after exposing to UV illumination for 500 hours, while the devices with pristine TiO2 lost the majority of their original PCEs in 150 hours. As a proof-of-concept, we further demonstrate the scalability of our method by fabricating a large-area Eu-TiO2 film of 64 cm2 showing excellent uniformity.
关键词： band alignment,planar perovskite solar cells,down-shifting,europium-doped titanium dioxide,UV stability
更新于2025-09-12 10:27:22
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The Impact of Mobile Ions on the Steady State Performance of Perovskite Solar Cells
摘要： Mobile ions in perovskite solar cells induce many unique transient phenomena, while their influence under steady-state, the primary operating condition, has received little attention. Therefore, in this work we employ ionic-drift diffusion models to assess how the steady-state distribution of mobile ions affects the photogenerated carrier collection, and their redistribution due to dopants and energy band alignment. We demonstrate that mobile ions can transform the carrier transport mechanism from a combination of drift and diffusion to transport by diffusion only, which only impacts the device efficiency if the carrier mobility-lifetime product is limited due to increased transport losses and changed recombination dynamics. A high concentration of dopants is also required in perovskite devices for such doping to have a measurable impact while the energy alignment of the transport layers, on the other hand, can in principle result in a doping-like effect, which generally causes adverse consequences for cell efficiency.
关键词： dopants,steady-state performance,perovskite solar cells,energy band alignment,mobile ions,carrier transport
更新于2025-09-12 10:27:22
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Valence-State Controllable Fabrication of Cu <sub/> 2– <i>x</i> </sub> O/Si Type-II Heterojunction for High-Performance Photodetectors
摘要： Cuprite, nominally cuprous oxide (Cu2O) but more correctly Cu2-xO, is widely used in optoelectronic applications due to its natural p-type, nontoxicity and abundant availability. However, the photoresponsivity of Cu2O/Si photodetectors (PDs) has been limited by the lack of high-quality Cu2-xO films. Herein, we report a facile room-temperature solution method to prepare high-quality Cu2-xO films with controllable x value which were used as hole selective transport layers in crystalline n-type silicon based heterojunction PDs. The detection performance of Cu2-xO/Si PDs exhibits a remarkable improvement via reducing the x value, resulting in the optimized PDs with high responsivity of 417 mA W-1 and fast response speed of 1.3 μs. Furthermore, the performance of the heterojunction PDs can be further improved by designing the pyramidal silicon structure, with enhanced responsivity of 600 mA W-1 and response speed of 600 ns. The superior photodetecting performance of Cu2-xO/n-Si heterojunctions is attributed to (i) the matched energy level band alignment, (ii) the low trap states in high-quality Cu2O thin films, (iii) the excellent light trapping. We expect the low-cost, highly efficient solution process would be of great convenience for large-scale fabrication of the Cu2-xO thin films and broaden the applications of Cu2-xO based optoelectronic devices.
关键词： photodetector,energy band alignment,Cuprous oxide,solution method,heterojunction
更新于2025-09-12 10:27:22
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A low-temperature TiO2/SnO2 electron transport layer for high-performance planar perovskite solar cells; 低温 TiO2/SnO2 双电子传输层的光电性能及其在 钙钛矿电池中的应用;
摘要： Conventional titanium oxide (TiO2) as an electron transport layer (ETL) in hybrid organic-inorganic perovskite solar cells (PSCs) requires a sintering process at a high temperature to crystalize, which is not suitable for flexible PSCs and tandem solar cells with their low-temperature-processed bottom cell. Here, we introduce a low-temperature solution method to deposit a TiO2/tin oxide (SnO2) bilayer towards an efficient ETL. From the systematic measurements of optical and electronic properties, we demonstrate that the TiO2/SnO2 ETL has an enhanced charge extraction ability and a suppressed carrier recombination at the ETL/perovskite interface, both of which are beneficial to photo-generated carrier separation and transport. As a result, PSCs with TiO2/SnO2 bilayer ETLs present higher photovoltaic performance of the baseline cells compared with their TiO2 and SnO2 single-layer ETL counterparts. The champion PSC has a power conversion efficiency (PCE) of 19.11% with an open-circuit voltage (Voc) of 1.15 V, a short-circuit current density (Jsc) of 22.77 mA cm?2, and a fill factor (FF) of 72.38%. Additionally, due to the suitable band alignment of the TiO2/SnO2 ETL in the device, a high Voc of 1.18 V is achieved. It has been proven that the TiO2/SnO2 bilayer is a promising alternative ETL for high efficiency PSCs.
关键词： electron transport layer,low temperature,perovskite solar cell,energy band alignment,TiO2/SnO2
更新于2025-09-12 10:27:22
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Enhancing PbS Colloidal Quantum Dot Tandem Solar Cell Performance by Graded Band Alignment
摘要： Colloidal quantum dot solids are attractive candidates for tandem solar cells because of their widely tunable bandgaps. However, the development of quantum dot tandem solar cell has lagged far behind that of its single-junction counterpart. One of the fundamental problems with colloidal quantum dot solar cells is the relatively small diffusion length, which limits the quantum dot absorbing layer thickness and hence the power conversion efficiency. In this research, guided by optical modelling and utilising a graded band alignment strategy, a two-terminal monolithic solution-processed quantum dot tandem solar cell has been successfully fabricated and a power conversion efficiency of 6.8% has been achieved. The band grading approach utilised the complementary tuning of work functions and band alignment through judicious choices of the nanoparticle surface chemistry and quantum dot confined size. This work demonstrates a general approach to improving the efficiency for tandem thin film solar cells.
关键词： tandem solar cells,optical modelling,Colloidal quantum dot solids,graded band alignment,power conversion efficiency
更新于2025-09-11 14:15:04
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Benzodithiophene-Thienopyrroledione-Thienothiophene-based Random Copolymeric Hole Transporting Material for Perovskite Solar Cell
摘要： Hole transport materials (HTMs) with different hole extraction abilities play an important role in dictating the efficiency of the perovskite solar cells (PSCs). Besides, employing a donor acceptor (D-A) random copolymer HTM to bring out deeper HOMO energy level is highly beneficial to the hole extraction and durability of PSCs. In this context, a highly soluble D-A based random copolymeric benzodithiophene-thienopyrroledione-Thienothiophene derivatives (RCP-BTT) HTM has been derived from the backbone structure of Poly({4,8-bis[(2ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7). The synthesized dopant-free RCP-BTT HTM shows a deeper HOMO energy level (-5.28 eV) due to its high compatibility than PTB7 level (-5.15 eV) based on perovskite energy level. Gradient band alignment of RCP-BTT has provided efficient hole extraction in the PSCs made of Cs-containing triple cation perovskite as absorber resulting in the efficient photovoltaic performance of RCP-BTT. The RCP-BTT with dopant shows significantly increased Voc (1.09 V) with respect to that of parent PTB7 (Voc of 1.06 V), resulting in an enhanced efficiency of 14.57% than that of PTB7 (12.02%). On the whole, the improvement in photovoltaic performance of PSC based on the polymeric RCP-BTT HTM is attributable to its deeper HOMO energy level and exceptional hole extraction ability.
关键词： Random copolymer,band alignment,mixed cation,hole extraction,perovskite solar cells
更新于2025-09-11 14:15:04
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Comparative study of photoluminescence for type-I InAs/GaAs0.89Sb0.11 and type-II InAs/GaAs0.85Sb0.15 quantum dots
摘要： InAs quantum dots (QDs) sandwiched inside a GaAsSb matrix possess advantages for achieving telecom wavelength lasers and for developing high efficiency solar cells. In this work, optical properties of InAs quantum dots (QDs) capped by GaAs1-xSbx (x ? 0.11 and 0.15) are comparatively investigated. The photoluminescence measurements reflect that the energy state filling, thermal activation, quenching, and lifetime of the carriers in InAs/GaAs0.89Sb0.11 QDs are different from those in the InAs/GaAs0.85Sb0.15 QDs. These differences are attributed to the band alignment transition from type-I to type-II resulting from the Sb-composition change from x ? 0.11 to x ? 0.15 in the GaAs1-xSbx capping layer. Therefore, the emission and quenching involve excited states for type-I InAs/GaAs0.85Sb0.15 QDs, but involve InAs QDs as well as the GaAs0.85Sb0.15 QW recombination for type-II InAs/GaAs0.85Sb0.15 QDs. So the luminescence reveals complex and distinct physics mechanisms for these two samples.
关键词： Photoluminescence,Quantum dots,Band alignment,Semiconductor compound
更新于2025-09-11 14:15:04
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Band alignment of atomic layer deposited SiO <sub/>2</sub> on (010) (Al <sub/>0.14</sub> Ga <sub/>0.86</sub> ) <sub/>2</sub> O <sub/>3</sub>
摘要： The (AlxGa1?x)2O3/Ga2O3 system is attracting attention for heterostructure ?eld effect transistors. An important device design parameter is the choice of gate dielectric on the (AlxGa1?x)2O3 and its band alignment at the heterointerface. The valence band offset at the SiO2/(Al0.14Ga0.86)2O3 heterointerface was measured using x-ray photoelectron spectroscopy. The SiO2 was deposited by atomic layer deposition (ALD) onto single-crystal β-(Al0.14Ga0.86)2O3 grown by molecular beam epitaxy. The bandgap of the SiO2 was determined by re?ection electron energy loss spectroscopy as 8.7 eV, while high resolution XPS data of the O 1s peak and onset of elastic losses were used to establish the (Al0.14Ga0.86)2O3 bandgap as 5.0 eV. The valence band offset was determined to be 1.60 ± 0.40 eV (straddling gap, type I alignment) for ALD SiO2 on β-(Al0.14Ga0.86)2O3. The conduction band offset was 2.1 ± 0.08 eV, providing for a strong electron transport restriction.
关键词： x-ray photoelectron spectroscopy,(Al0.14Ga0.86)2O3,SiO2,atomic layer deposition,conduction band offset,band alignment,valence band offset
更新于2025-09-10 09:29:36
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Tuning the band alignment of p-type graphene-AsSb Schottky contact by electric field
摘要： By combining the electronic structures of graphene and monolayer AsSb via van der Waals force interaction, the intrinsic p-type Schottky contact can be obtained. Here, a series of theoretic calculations are performed to survey the effects of interlayer coupling and the band realignment of graphene-AsSb heterointerface. It reveals that intrinsic p-type Schottky barriers of 0.184 and 0.381 eV are formed for the two types of configurations. Besides, the intrinsic electronic properties of graphene and AsSb are roughly preserved. When the external electric field is applied, the Schottky barrier can be effectively tuned up by changing the external electric field intensity and further convert the p-type contact into the n-type contact. A variation of the Schottky barriers indicates a partial Fermi level pinning at the interfaces of AsSb. It results from the low density of interfacial states between graphene and AsSb. The barrier height of AsSb and the corresponding contact type can be flexibly tuned, which is of great importance in the design of novel transistors based two-dimensional materials and they provide meaningful guidelines.
关键词： AsSb,electric field,graphene,band alignment,Schottky contact
更新于2025-09-09 09:28:46
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Design and Comparative Studies of Z-Scheme and Type II Based Heterostructures of NaNbO <sub/>3</sub> /CuInS <sub/>2</sub> /In <sub/>2</sub> S <sub/>3</sub> for Efficient Photoelectrochemical Applications
摘要： Here, we report the fabrication of a new Z-scheme based core/shell/shell heterostructure of NaNbO3/CuInS2/In2S3 (core/shell/shell) for photoelectrochemical (PEC) water splitting and also for degradation of organic pollutants. We have also performed a comparative study with a modified heterostructure of NaNbO3/In2S3/CuInS2 having Type II band alignment. The PEC measurements under visible light irradiation show increased photocatalytic performance for the NaNbO3/CuInS2/In2S3 heterostructures as revealed by a high current density of ～6.72 mA/cm2 at ?1.0 V versus Ag/AgCl and low photocurrent onset potential of ～?110 mV in comparison to the Type II system (～1.63 mA/cm2 and ?180 mV vs Ag/AgCl). Mott?Schottky plots confirmed the n?p?n type heterojunction formation in the NaNbO3/CuInS2/In2S3 heterostructure which reduces the charge carrier recombination (revealed by PL intensity and short lifetime). The Z-scheme based system also exhibits excellent degradation efficiency (～99.6%) of organic pollutants. This work shows that the Z-scheme charge separation mechanism in NaNbO3/CuInS2/In2S3 nanostructures is more efficient than the Type II based on NaNbO3/In2S3/CuInS2.
关键词： core/shell/shell heterostructure,photoelectrochemical water splitting,Type II band alignment,organic pollutants degradation,Z-scheme,NaNbO3/CuInS2/In2S3
更新于2025-09-09 09:28:46