- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
An Experimental and Theoretical Study into Interface Structure and Band Alignment of the Cu2Zn1-xCdxSnS4 Heterointerface for Photovoltaic Applications
摘要： To improve the constraints of kesterite Cu2ZnSnS4 (CZTS) solar cell, such as undesirable band alignment at p?n interfaces, bandgap tuning, and fast carrier recombination, cadmium (Cd) is introduced into CZTS nanocrystals forming Cu2Zn1-xCdxSnS4 through cost-effective solution-based method without post-annealing or sulfurization treatments. A synergetic experimental-theoretical approach was employed to characterize and assess the optoelectronic properties of Cu2Zn1-xCdxSnS4 materials. Tunable direct band gap energy ranging from 1.51 eV to 1.03 eV with high absorption coefficient was demonstrated for the Cu2Zn1-xCdxSnS4 nanocrystals with changing Zn/Cd ratio. Such bandgap engineering in Cu2Zn1-xCdxSnS4 helps in effective carrier separation at interface. Ultrafast spectroscopy reveals a longer lifetime and efficient separation photo-excited charge carriers in Cu2CdSnS4 (CCTS) nanocrystals compared to that of CZTS. We found that there exists a type-II staggered band alignment at the CZTS (CCTS)/CdS interface, from cyclic voltammetric (CV) measurements, corroborated by first-principles density functional theory (DFT) calculations, predicting smaller conduction band offset (CBO) at the CCTS/CdS interface as compared to the CZTS/CdS interface. These results point towards efficient separation of photoexcited carriers across the p?n junction in the ultrafast time scale and highlight a route to improve device performances.
关键词： grain boundary,photovoltaic,cation substitution,Earth-abundant material,interfacial engineering,band offset,ultrafast carrier dynamics
更新于2025-09-23 15:21:01
-
Bis(4-methylthio)phenyl)amine-based hole transport materials for highly-efficient perovskite solar cells: insight into the carrier ultrafast dynamics and interfacial transport
摘要： Hole transport layers (HTLs) play a significant role in the performance of perovskite solar cells. A new class of linear small-molecules based on bis(4-methylthio)phenyl)amine as an end group, carbon, oxygen and sulfur as the center atoms for the center unit (denoted as MT-based small-molecule), respectively, have been applied as HTL, and two of them presented the efficiency over 20% in the planar inverted perovskite solar cells (PSCs), which demonstrated a significant improvement in comparison with the widely used HTL, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (known as PEDOT:PSS), in the planar inverted architecture. The ultrafast carrier dynamics show that the excited hot carrier cooling process of MT-based small-molecule HTL samples is faster than that of PEDOT:PSS samples. The kinetic analysis of photo-bleaching peaks of femtosecond transient absorption spectra reveals that the traps at the interface between MT-based small-molecule HTLs and MAPbI3 can be filled much quicker than that at PEDOT/MAPbI3 interfaces. Moreover, the hole injection time from MAPbI3 to MT-based small-molecule HTLs is around 10 times quicker than that to PEDOT:PSS. Such quick trap filling and hole extraction bring a significant enhancement in photovoltaic performances. These findings uncover the carrier transport mechanisms and illuminate a promising approach for the design of new HTLs for highly-efficient perovskite solar cells.
关键词： hole transport layer,perovskite solar cell,ultrafast carrier dynamics
更新于2025-09-23 15:21:01
-
Ultrafast Charge Carrier Dynamics and Nonlinear Optical Absorption of InP/ZnS Core-Shell Colloidal Quantum Dots
摘要： Understanding of ultrafast carrier dynamics in InP/ZnS colloidal quantum dots (QDs) is essential for their optoelectronic applications. In this paper, we have successfully fabricated high-quality InP/ZnS core-shell QDs with quantum yield (QY) of 47%. Time resolved photoluminescence (TRPL), femtosecond transient absorption (TAS) measurements were performed to characterize the carrier injection, relax and transition process in the InP/ZnS QDs. It is found that the photoexcited carrier first injected to ZnS shell in 2 ps, then relaxed to alloyed layer between ZnS shell and InP core in 7.4 ps, next relaxed to different energy levels in InP core in about 170 ps, finally recombined by charged and neutral excitons transition in 4.1 ns and 26.7 ns, respectively. Additionally, the two-photon absorption (TPA) coefficient obtained from Z-scan measurement indicates that InP/ZnS QDs possess good nonlinearly optical properties. Our research is significant for the improvement and engineering of InP/ZnS QDs based materials for optoelectronic applications.
关键词： quantum dots,InP/ZnS,ultrafast carrier dynamics,nonlinear optical absorption,optoelectronic applications
更新于2025-09-19 17:13:59
-
Probing the upper band gap of atomic rhenium disulfide layers
摘要： Here, we investigate the ultrafast carrier dynamics and electronic states of exfoliated ReS2 films using time-resolved second harmonic generation (TSHG) microscopy and density functional theory (DFT) calculations. The second harmonic generation (SHG) of layers with various thicknesses is probed using a 1.19-eV beam. Up to ~13 nm, a gradual increment is observed, followed by a decrease caused by bulk interferometric light absorption. The addition of a pump pulse tuned to the exciton band gap (1.57 eV) creates a decay-to-rise TSHG profile as a function of the probe delay. The power and thickness dependencies indicate that the electron–hole recombination is mediated by defects and surfaces. The two photon absorptions of 2.38 eV in the excited state that are induced by pumping from 1.57 to 1.72 eV are restricted because these transitions highly correlate with the forbidden d–d intrasubshell orbital transitions. However, the combined usage of a frequency-doubled pump (2.38 eV) with wavelength-variant SHG probes (2.60–2.82 eV) allows us to vividly monitor the variations in TSHG profiles from decay-to-rise to rise-to-decay, which imply the existence of an additional electron absorption state (s-orbital) at an approximate distance of 5.05 eV from the highest occupied molecular orbital states. This observation was critically examined by considering the allowance of each electronic transition and a small upper band gap (~0.5 eV) using modified DFT calculations.
关键词： density functional theory,ReS2,time-resolved spectroscopy,ultrafast carrier dynamics,second harmonic generation
更新于2025-09-09 09:28:46