⇦Chinese Physics Letters, 2020, Vol. 37, No. 10, Article code 108401 Antimony Selenide Thin Film Solar Cells with an Electron Transport Layer of Alq$_{3}$ Wen-Jian Shi (师文建)1, Ze-Ming Kan (阚泽明)1, Chuan-Hui Cheng (程传辉)2*, Wen-Hui Li (李文慧)2, Hang-Qi Song (宋航琪)2, Meng Li (李萌)2, Dong-Qi Yu (于东麒)1*, Xiu-Yun Du (杜秀云)1, Wei-Feng Liu (刘维峰)3, Sheng-Ye Jin (金盛烨)4, and Shu-Lin Cong (丛书林)2 Affiliations 1School of Physics and Electronic Technology, Liaoning Normal University, Dalian 116029, China 2School of Physics, Dalian University of Technology, Dalian 116024, China 3Mechanical and Electrical Engineering College, Hainan University, Haikou 570228, China 4State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 China Received 14 July 2020; accepted 31 August 2020; published online 29 September 2020 Supported by the High Level Talents Project of Hainan Basic and Applied Research Program (Natural Science) (Grant No. 2019RC118), and the Open Fund of the State Key Laboratory of Molecular Reaction Dynamics in DICP (Grant No. SKLMRD-K202005).
*Corresponding authors. Email: chengchuanhui@dlut.edu.cn; useeu@163.com Citation Text: Shi W J, Han Z M, Cheng C H, Li W H and Song H Q et al. 2020 Chin. Phys. Lett. 37 108401    Abstract We fabricated Sb$_{2}$Se$_{3}$ thin film solar cells using tris(8-hydroxy-quinolinato) aluminum (Alq$_{3}$) as an electron transport layer by vacuum thermal evaporation. Another small organic molecule of N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)benzidine (NPB) was used as a hole transport layer. We took ITO/NPB/Sb$_{2}$Se$_{3}$/Alq$_{3}$/Al as the device architecture. An open circuit voltage ($V_{\rm oc}$) of 0.37 V, a short circuit current density ($J_{\rm sc}$) of 21.2 mA/cm$^{2}$, and a power conversion efficiency (PCE) of 3.79% were obtained on an optimized device. A maximum external quantum efficiency of 73% was achieved at 600 nm. The $J_{\rm sc}$, $V_{\rm oc}$, and PCE were dramatically enhanced after introducing an electron transport layer of Alq$_{3}$. The results suggest that the interface state density at Sb$_{2}$Se$_{3}$/Al interface is decreased by inserting an Alq$_{3}$ layer, and the charge recombination loss in the device is suppressed. This work provides a new electron transport material for Sb$_{2}$Se$_{3}$ thin film solar cells. DOI:10.1088/0256-307X/37/10/108401 PACS:84.60.Jt, 85.30.De © 2020 Chinese Physics Society Article Text Energy and environmental problems are serious concerns that have driven the urgent need to develop cheap and clean energy sources such as solar cells. Thin film solar cells based on CdTe and CuIn$_{1-y}$Ga$_{y}$Se$_{2}$ (CIGS) have achieved high power conversion efficiencies (PCEs) of more than 20%.[1,2] Yet, concerns remain on the scarcity of Te, the toxicity of Cd, and high price of In and Ga.[3] Hence, it is essential to find cheap, earth-abundant, and low-toxicity materials for applications in solar cells. In recent years, antimony selenide (Sb$_{2}$Se$_{3}$) has received considerable attention because of its low toxicity, earth abundance, suitable band gap (1.03 eV indirect and 1.17 eV direct),[4] high absorption coefficient ($>$$10^{5}$ cm$^{-1}$ at around 600 nm),[5] single phase structure, and inert grain boundaries. In Sb$_{2}$Se$_{3}$ crystal, (Sb$_{4}$Se$_{6})_{n}$ ribbons stack along the $\langle 001\rangle$ direction through strong covalent Sb–Se bonds, whereas the (Sb$_{4}$Se$_{6})_{n}$ ribbons are held together by van der Waals forces in the $\langle 100\rangle$ and $\langle 010\rangle$ directions.[6] Various methods have been used to deposit Sb$_{2}$Se$_{3}$ thin films, such as vacuum thermal evaporation,[7] rapid thermal evaporation,[8] vapor transport deposition,[9,10] magnetron sputtering,[11,12] closed space sublimation,[13,14] electrodeposition,[15] and solution processing method.[16–21] The Sb$_{2}$Se$_{3}$ solar cell was first reported by Nair et al. in 2009, and the PCE was only 0.66%.[22] In past years, the device efficiency has been gradually improved. Luo et al.[7] fabricated a Sb$_{2}$Se$_{3}$ thin film solar cells with a PCE of 1.9% by vacuum thermal evaporation in 2014. In the same year, they improved the PCE to 3.7% by an additional selenization step.[23] In 2015, a PCE of 5.6% was obtained by Zhou et al. using the rapid thermal evaporation technique.[8] Choi et al.[16] have achieved a PCE of 6.4% via the solution processing method. In 2018, Wen et al.[9] achieved a PCE of 7.6% using the vapor transport deposition technique. A record PCE of 9.2% was created by Li et al. in 2019 using closed space sublimation.[24] This record efficiency of 9.2% is still much lower than its Shockley–Queisser limit of higher than 30%.[25–27] Therefore, further research is still required to improve the performance of the Sb$_{2}$Se$_{3}$ thin film solar cells. The crystal grains sizes are relatively large in the polycrystal films fabricated by both the rapid thermal evaporation[8] and closed space sublimation.[13,14] However, the deposition rates are so high ($\sim $8 nm/s) that the Sb and Se atoms cannot relax to their equilibrium sites, leading to the pinholes, defects, and wild orientations of the (Sb$_{4}$Se$_{6}$)$_{n}$ chains in different crystal grains. In term of the vapor transfer deposition, the optimized deposition rate is also very high.[9] The high deposition rate may result in the wild orientations of (Sb$_{4}$Se$_{6}$)$_{n}$ chains and bad quality of the film. Hydrothermal deposition technique[21] allows moderate experimental condition (135 ℃) and low nucleation rate, which results in the large size of the crystal grains and good device performance. At present, for the films fabricated by the vacuum thermal evaporation followed post annealing, the crystal grains sizes are relatively small, and the preferred orientation of (020) is unfavored for the charge transport. However, the film with a preferred orientation of (001) and higher efficiency will be realized by the surface modification of substrate, introduction of buffer layer, and post treatment. Sb$_{2}$Se$_{3}$ is a p-type semiconductor. Thus, the electron extraction is crucial for Sb$_{2}$Se$_{3}$ film solar cells. Numerous electron transport materials such as CdS,[7] Zn-doped CdS,[28] In-doped CdS,[29] ZnO,[30] TiO$_{2}$,[31] SnO$_{2}$,[32] and PCBM[33,34] have been used in Sb$_{2}$Se$_{3}$ thin film solar cells. Small organic molecules of tris(8-hydroxy-quinolinato) aluminum (Alq$_{3}$) are a famous electron transport material in organic light-emitting diodes, and can be easily deposited by vacuum thermal evaporation. In this work, we fabricated Sb$_{2}$Se$_{3}$ thin film solar cells using tris(8-hydroxy-quinolinato) aluminum (Alq$_{3}$) as an electron transport layer by vacuum thermal evaporation. Another small organic molecule of N,N'-bis(naphthalen-1-yl)-N,N'-bis (phenyl) benzidine (NPB) was used as a hole transport layer, and a PCE of 3.79% was achieved, which is much higher than that of the device without an Alq$_{3}$ layer. In most of the devices reported previously, transparent conductive oxide (TCO) is used as cathode, and noble metal Au is used as anode. However, TCO was used as anode in our device, and metal Al was used as a cathode, reducing the cost of the device.
cpl-37-10-108401-fig1.png
Fig. 1. (a) Device architecture and molecular structures. (b) Energy-level diagram of the device.
Sb$_{2}$Se$_{3}$ (99.99%) was purchased from Sigma. Alq$_{3}$ (sublimed grade, $\ge$99.0%) and NPB (sublimed grade, $\ge$99.0%) were purchased from Nichem Corp. Solar cells were fabricated by vacuum thermal evaporation ($ < $$5.0\times 10^{-4}$ Pa) on commercially patterned indium tin oxide (ITO) coated glass with a sheet resistance less than 8 $\Omega$/cm$^{2}$. Substrates were ultrasonically washed in acetone, alcohol and deionized water in sequence, and then dried by a flow of nitrogen gas. Next, NPB and Sb$_{2}$Se$_{3}$ were successively deposited by vacuum thermal evaporation. Then, vacuum was broken and substrates were transferred to a vacuum tube furnace with two temperature zones to anneal in the atmosphere of Se at 280 ℃ for 30 min, and was naturally cooled down to room temperature. During selenization the source of Se was kept at 210 ℃, and the nitrogen gas was introduced to tube with a flux of 30 sccm and a pressure of $\sim $35 Pa. After that, Alq$_{3}$, and Al electrode were successively deposited by vacuum thermal evaporation. A stainless shadow mask was used to define the device profile ($1.5 \times 5.0$ mm$^{2}$). During vacuum evaporation, film thickness was monitored by a quartz crystal microbalance. The deposition rates were $\sim 0.2$ nm/s for the organic and Sb$_{2}$Se$_{3}$ films. The device and molecular structures are shown in Fig. 1(a). A diagram of the device energy levels is depicted in Fig. 1(b). Transmittance measurements were conducted using a Shimadzu UV3600 spectrophotometer. X-ray diffraction (XRD) was performed on a Shimadzu XRD-6100. Scanning electron microscopy (SEM) images were obtained on a Zeiss SUPARR-5503040702. Atomic force microscopy images were obtained on a Bruker Dension Icon. The photovoltaic response was measured using a Keithley 2611A source meter under AM1.5 illumination from a Zolix Sirius-SS150A solar simulator (China) at a power density of 100 mW/cm$^{2}$. The irradiation intensity on the cells was adjusted by a standard calibrated Si solar cell. External quantum efficiency (EQE) was measured on a Zolix SCS100 analyzer. The capacitance-voltage ($C$–$V$) characteristics were measured on an Agilent B1500A semiconductor device analyzer in the darkness, where an alternating current voltage of 30 mV and direct current bias voltage varying from $-0.8$ V to 0.4 V were applied during the measurement. The transient photovoltage (TPV) signals were monitored by a Keysight DSOX3012 T digital oscilloscope. During the TPV measurement, the device was illuminated by laser pulses (532 nm, 5-ns width, 8 Hz, New Wave), and a background white light (50 mW/cm$^{2}$) from a xenon lamp was used to hold the carrier density. All measurements were carried out at room temperature. Figure 2(a) shows the transmittance spectrum of the Sb$_{2}$Se$_{3}$ film. The absorption of the Sb$_{2}$Se$_{3}$ film covers the ultraviolet, visible, and near-infrared regions. We obtained the optical band gap of the Sb$_{2}$Se$_{3}$ thin film using the following relation: $$ (\beta h\nu)^{2}=A(h\nu -E_{\rm g}),~~ \tag {1} $$ where $\beta$ is the absorption coefficient at a frequency of $v$, $h$ is the Plank constant, $E_{\rm g}$ is the optical band gap, and $A$ is a constant. The curve of ($\beta h\nu$)$^{2}$–$h\nu$ is given in the insert of Fig. 2(a), which exhibits a linear zone. An optical band gap of 1.25 eV is obtained from the horizontal intercept, which is closed to the results reported by other groups.[4] Absorption spectra of NPB and Alq$_{3}$ films are shown in Fig. 2(b).
cpl-37-10-108401-fig2.png
Fig. 2. (a) Transmission spectrum of the Sb$_{2}$Se$_{3}$ film. Inset: curve of ($\beta h \nu$)$^{2}$–$h\nu$ for the Sb$_{2}$Se$_{3}$ film. (b) Absorption spectra of NPB and Alq$_3$ film.
cpl-37-10-108401-fig3.png
Fig. 3. XRD patterns of the Sb$_{2}$Se$_{3}$ film with and without an annealing treatment.
To characterize the crystal structure and surface morphology of the Sb$_{2}$Se$_{3}$ films we performed the XRD and SEM measurements. Figure 3 shows the XRD patterns of the Sb$_{2}$Se$_{3}$ film with and without an annealing treatment. For the film without an annealing process, no diffraction feature was observed, which indicated an amorphous film. Meanwhile, for the film with an annealing process, a strong $\langle 020\rangle$ diffraction peak was observed at 2$\theta = 14.9^{\circ}$ with a full width at half maximum of 0.22 ℃ (JCPDS 15–0816). The XRD pattern shows no other diffraction peak, which indicates a preferred orientation of the $\langle 020\rangle$ crystal plane. Figures 4(a)–4(d) display the SEM surface and cross-sectional images of the Sb$_{2}$Se$_{3}$ films with and without an annealing treatment. As can be seen, without an annealing treatment, the Sb$_{2}$Se$_{3}$ film exhibited a very smooth surface and cross section without any texture. However, for the Sb$_{2}$Se$_{3}$ film with an annealing treatment, grain boundaries are clearly observed, and textures are parallel to the film surface. We also observed that the texture directions vary from grain to grain. The sizes of some grains are more than 1 µm. AFM surface morphologies were also measured, and the images are shown in Figs. 4(e) and 4(f). The rms roughness of the Sb$_{2}$Se$_{3}$ films is slightly increased from 0.927 to 2.08 nm after an annealing treatment. The crystal grains are also observed after an annealing treatment, which are consistent with the SEM and XRD measurements. The results suggest that an annealing treatment can significantly improve the crystal quality of the Sb$_{2}$Se$_{3}$ film.
cpl-37-10-108401-fig4.png
Fig. 4. [(a),(b)] SEM surface images and [(c),(d)] cross-sectional views of the Sb$_{2}$Se$_{3}$ films deposited on ITO coated glass substrates [(a),(c)] without and [(b),(d)] with an annealing treatment. AFM surface images of the Sb$_{2}$Se$_{3}$ film deposited on ITO coated glass substrates without (e) and with (f) an annealing treatment.
We next fabricated the solar cells with the architecture of ITO/NPB (6.0 nm)/Sb$_{2}$Se$_{3}$ (150 nm)/Alq$_{3}$ (3.0 nm)/Al. Here, NPB was used as a hole transport layer, and Alq$_{3}$ was served as an electron transport layer. We also prepared a controlled cell without an Alq$_{3}$ layer for comparison. The hole mobility of NPB varied from $1.63\times 10^{-5}$ to $7.64\times 10^{-4}$ cm$^{-2}$$\cdot $V$^{-1}$$\cdot$s$^{-1}$ as the film thickness increased from 50 to 1000 nm.[35] The electron mobility of Alq$_{3}$ is on an order of magnitude of 10$^{-6}$ cm$^{-2}$$\cdot $V$^{-1}$$\cdot$s$^{-1}$.[36] The optimized thickness of NPB and Alq$_{3}$ less than 10 nm in the cell because of their low carrier mobilities. The $J$–$V$ curves of the solar cells with and without the Alq$_{3}$ layer under one sun illumination (AM 1.5, 100 mW/cm$^{2}$) are shown in Fig. 5(a). Device performance parameters are summarized in Table 1. By introducing an electron transport layer of Alq$_{3}$, the $V_{\rm oc}$, $J_{\rm sc}$, FF, and PCE of the device are significantly improved. An open circuit voltage ($V_{\rm oc}$) of 0.37 V, a short circuit current density ($J_{\rm sc}$) of 21.2 mA/cm$^{2}$, fill factor (FF) of 48%, and a PCE of 3.79% are obtained on an optimized device. The PCE was increased by 72% after introducing an Alq$_{3}$ layer.
Table 1. Summary of the cell performance parameters extracted from $J$–$V$ curves.
Cell structure $V_{\rm oc}$ (V) $J_{\rm sc}$ (mA/cm$^{2}$) FF $R_{\rm s}$ ($\Omega$/cm$^{2}$) $J_{0}$ (mA/cm$^{2}$) $n$ PCE
With Alq$_{3}$ 0.37 21.2 0.48 2.18 $8.9\times 10^{-3}$ 2.07 3.79%
Without Alq$_{3}$ 0.30 18.2 0.40 2.37 $1.4\times 10^{-2}$ 1.93 2.20%
cpl-37-10-108401-fig5.png
Fig. 5. $J$–$V$ curves of solar cells with and without an Alq$_{3}$ layer (a) under light (AM 1.5, 100 mW/cm$^{2}$) and (b) in the darkness. (c) $C$–$f$ and (d) $C^{-2}$–$V$ characteristics of the device with and without an Alq$_{3}$ layer in the darkness.
To explain the enhanced performance by introducing an Alq$_{3}$ layer, we measured the $J$–$V$ characteristics of the device with and without an Alq$_{3}$ layer in the darkness, and the results are given in Fig. 5(b). $J$ of the device can be described by Eq. (2), which is the modified Shockley equation where a series resistance $R_{\rm s}$ is considered. Equation (3) can be easily deduced from Eq. (2), which suggests that a lower reverse saturation current density ($J_{0}$) means a higher $V_{\rm oc}$. $$ J=J_{0} \Big\{ {\exp \Big[ {\frac{q(V-JR_{\rm s})}{nk_{_{\rm B}} T}} \Big]-1} \Big\}-J_{\rm ph},~~ \tag {2} $$ $$ V_{\rm oc} \approx \frac{nk_{_{\rm B}} T}{q}\ln \frac{J_{\rm sc} }{J_{0} },~~ \tag {3} $$ where $J_{0}$ is the reverse saturation current density, $q$ is the charge of an electron, $n$ is the ideal factor, $k_{_{\rm B}}$ is the Boltzmann constant, $T$ is the temperature, and $J_{\rm ph}$ is the photo-current density. After introducing an Alq$_{3}$ layer, the current densities under reverse bias are decreased. The $J$–$V$ curves are fitted with Eq. (2), and the fit parameters are given in Table 1. The $J_{0}$ are decreased from $1.4\times 10^{-2}$ to $8.9\times 10^{-3}$ mA/cm$^{2}$ by introducing an Alq$_{3}$ layer. The decreased $J_{0}$ indicates a reduced recombination loss and an enhanced $V_{\rm oc}$. As shown in Fig. 1(b), the lowest unoccupied molecular orbital (LUMO) level of NPB ($-$2.4 eV) is much higher than the conductance band edge of Sb$_{2}$Se$_{3}$, which can block the photo-generated electron diffusion from Sb$_{2}$Se$_{3}$ to ITO and then suppress the recombination near the anode. Meanwhile, the relatively low highest occupied molecular orbital (HOMO) level of Alq$_{3}$ means that it can resist the hole diffusion from Sb$_{2}$Se$_{3}$ to Al, and consequently reduce the recombination loss near the cathode. Figures 5(c) and 5(d) shows the characteristics of capacitance-frequency ($C$–$f$) and $C^{-2}$–$V$ of the devices in the darkness. The capacitance of the device mainly comes from the junction, interface states, and bulk traps. At low frequency, all the interface states and bulk traps can vary with the alternating current (AC) signal applied. However, at higher frequencies, some interface states and bulk traps cannot be synchronized with the AC signal applied, and the measured capacitance will be decreased. As can be seen from Fig. 5(c), at lower frequencies, the capacitance of devices with an Alq$_{3}$ layer is smaller than that of the device without an Alq$_{3}$ layer, which indicates that the interface state density is decreased by introducing an Alq$_{3}$ layer (because the bulk trap densities were same). For the abrupt heterojunction, the relation between its capacitance and carrier density is as follows: $$ \frac{1}{C^{2}}=\frac{2\left( {\left. {V_{\rm bi} -V} \right)} \right.}{qA^{2}\varepsilon_{0} \varepsilon_{r} N_{\rm A} },~~ \tag {4} $$ where $V_{\rm bi}$ is the built-in potential, $A$ is the device area, $\varepsilon_{0}$ is the vacuum permittivity, $\varepsilon_{r}$ is the relative dielectric constant, and $N_{\rm A}$ is the carrier density. Figure 5(d) demonstrates the characteristics of $C^{-2}$–$V$ at a frequency of 100 kHz for the devices with and without an Alq$_{3}$ layer. The $V_{\rm bi}$'s of 0.50 and 0.45 V for the devices with and without an Alq$_{3}$ layer were obtained from the intercept of the horizontal axis. The result indicates that $V_{\rm bi}$ can be improved by inserting an Alq$_{3}$ layer. In addition, we performed the TPV measurements to elucidate the photo-generated charge recombination dynamics, and the results are shown in Fig. 6. The device with an Alq$_{3}$ layer showed a longer carrier lifetime (7.8 µs) than that without an Alq$_{3}$ layer (5.1 µs). According to the above results, we can conclude that the introduction of the Alq$_{3}$ layer can reduce the interface state density, suppress charge recombination, and enhance the device performance.
cpl-37-10-108401-fig6.png
Fig. 6. Transient photovoltage decay curves of the device with and without an Alq$_{3}$ layer.
To further investigate the wavelength response of the device, we measured the EQE of the device. Figure 7 shows the EQE spectrum of an optimized device. The device demonstrated a wide photoelectric response spectrum, which extended to $\sim $1000 nm, in agreement with the band gap of Sb$_{2}$Se$_{3}$. The maximum EQE of 73% was achieved at 600 nm. There is a valley near 420 nm, which was caused by the effect of film interference. We derived the current density of 20.0 mA/cm$^{2}$ by integrating the EQE with the standard AM1.5 solar spectrum, which was very close to the value of 21.2 mA/cm$^{2}$ obtained from $J$–$V$ measurement under the illumination from a solar simulator.
cpl-37-10-108401-fig7.png
Fig. 7. EQE spectrum of the optimized device.
To investigate the repeatability of the devices, we fabricated 100 solar cells. The distribution of the PCEs is demonstrated in Fig. 8. The difference in PCE between devices is small, and the PCEs show a normal distribution with an average of 3.02% and a variance of 0.36%.
cpl-37-10-108401-fig8.png
Fig. 8. Distribution of PCEs of 100 solar cells.
At present, $J_{\rm sc}$ of the Sb$_{2}$Se$_{3}$ film solar cells has reached a relatively high level. The lower $V_{\rm oc}$ is the main limited factor for the device performance. In all the reported results, the open circuit voltages are smaller than 0.5 V. In the future the three points below should be addressed to improve the $V_{\rm oc}$ of the device. (1) It is crucial to improve the crystal quality of the Sb$_{2}$Se$_{3}$ film and suppress the trap-assistant recombination. (2) The carrier mobilities are anisotropic in Sb$_{2}$Se$_{3}$ crystal. The carrier mobilities are the highest along the (001) direction. However, the preferred orientation is (020) in our film. The film with (001) preferred orientation is benefit for the device. (3) The $V_{\rm oc}$ is primarily determined by the Fermi level difference between Sb$_{2}$Se$_{3}$ and the n-type material. Therefore, higher $V_{\rm oc}$ can be obtained using the n-type material with a smaller work function. In addition, p-type doping can lower the Fermi level of the Sb$_{2}$Se$_{3}$, and consequently improve the $V_{\rm oc}$ of the cells. In summary, Alq$_{3}$ was used as an electron transport layer in the Sb$_{2}$Se$_{3}$ film solar cell. The PCE is increased by 72% by introducing an Alq$_{3}$ layer. The optimized device has a $V_{\rm oc}$ of 0.37 V, a $J_{\rm sc}$ of 21.2 mA/cm$^{2}$, and a PCE of 3.79%. A maximum EQE of 73% is achieved at 600 nm. The results suggest that adding an Alq$_{3}$ layer can reduce the interface state density, suppress the charge recombination, and consequently improve the device performance. This work provides a new electron transport material for Sb$_{2}$Se$_{3}$ film solar cells. References Solar cell efficiency tables (version 52)Effects of heavy alkali elements in Cu(In,Ga)Se 2 solar cells with efficiencies up to 22.6%Thermal Evaporation and Characterization of Sb 2 Se 3 Thin Film for Substrate Sb 2 Se 3 /CdS Solar CellsOptical properties of amorphous and polycrystalline Sb 2 Se 3 thin films prepared by thermal evaporationSolution-Processed Antimony Selenide Heterojunction Solar CellsThe crystal structure of antimony selenide, Sb2Se3Thermal evaporation and characterization of superstrate CdS/Sb 2 Se 3 solar cellsThin-film Sb2Se3 photovoltaics with oriented one-dimensional ribbons and benign grain boundariesVapor transport deposition of antimony selenide thin film solar cells with 7.6% efficiencyGrowth mechanism of Sb2Se3 thin films for photovoltaic application by vapor transport depositionFacile preparation and enhanced photoelectrical performance of Sb2Se3 nano-rods by magnetron sputtering depositionThermally induced structural evolution and performance of Sb2Se3 films and nanorods prepared by an easy sputtering method6.6% efficient antimony selenide solar cells using grain structure control and an organic contact layerStable and efficient CdS/Sb2Se3 solar cells prepared by scalable close space sublimationElectrodeposition of Antimony Selenide Thin Films and Application in Semiconductor Sensitized Solar CellsEfficient Sb 2 S 3 -Sensitized Solar Cells Via Single-Step Deposition of Sb 2 S 3 Using S/Sb-Ratio-Controlled SbCl 3 -Thiourea Complex SolutionHighly Improved Sb 2 S 3 Sensitized-Inorganic-Organic Heterojunction Solar Cells and Quantification of Traps by Deep-Level Transient SpectroscopyEfficient Inorganic-Organic Heterojunction Solar Cells Employing Sb 2 (S x /Se 1- x ) 3 Graded-Composition SensitizersPromising Sb 2 (S,Se) 3 Solar Cells with High Open Voltage by Application of a TiO 2 /CdS Double Buffer LayerElectrodeposition of Sb2Se3 on indium-doped tin oxides substrate: Nucleation and growthHydrothermal deposition of antimony selenosulfide thin films enables solar cells with 10% efficiencyAntimony Selenide Absorber Thin Films in All-Chemically Deposited Solar CellsSelenization of Sb 2 Se 3 absorber layer: An efficient step to improve device performance of CdS/Sb 2 Se 3 solar cells9.2%-efficient core-shell structured antimony selenide nanorod array solar cellsDetailed Balance Limit of Efficiency of p‐n Junction Solar CellsScalable Low-Band-Gap Sb 2 Se 3 Thin-Film Photocathodes for Efficient Visible–Near-Infrared Solar Hydrogen EvolutionPhotovoltaic materials: Present efficiencies and future challengesImprovement in Sb 2 Se 3 Solar Cell Efficiency through Band Alignment Engineering at the Buffer/Absorber InterfaceInterfacial Engineering by Indium-Doped CdS for High Efficiency Solution Processed Sb 2 (S 1– x Se x ) 3 Solar CellsStable 6%-efficient Sb2Se3 solar cells with a ZnO buffer layerAccelerated Optimization of TiO 2 /Sb 2 Se 3 Thin Film Solar Cells by High-Throughput Combinatorial ApproachSb 2 Se 3 Thin-Film Photovoltaics Using Aqueous Solution Sprayed SnO 2 as the Buffer LayerSpace-Charge Limited PhotocurrentOrigin of the light intensity dependence of the short-circuit current of polymer/fullerene solar cellsHole mobility of N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl) benzidine investigated by using space-charge-limited currentsNondispersive electron transport in Alq3
[1] Green M A, Hishikawa Y, Dunlop E D et al. 2018 Prog. Photovoltaics 26 427
[2] Jackson P, Wuerz R, Hariskos D et al. 2016 Phys. Status Solidi RRL 10 583
[3] Liu X, Chen J, Luo Met et al. 2014 ACS Appl. Mater. & Interfaces 6 10687
[4] Chen C, Li W, Zhou Y et al. 2015 Appl. Phys. Lett. 107 043905
[5] Zhou Y, Leng M, Xia Z et al. 2014 Adv. Energy Mater. 4 1301846
[6] Voutsas G P, Papazoglou A G, Rentzeperis P J and Siapkas D 1985 Z. Kristallogr. 171 261
[7] Luo M, Leng M, Liu X et al. 2014 Appl. Phys. Lett. 104 173904
[8] Zhou Y, Wang L, Chen S et al. 2015 Nat. Photon. 9 409
[9] Wen X, Chen C, Lu S et al. 2018 Nat. Commun. 9 2179
[10] Kondrotas R, Zhang J, Wang C and Tang J 2019 Sol. Energy Mater. Sol. Cells 199 16
[11] Liang G X, Zhang X H, Ma H L et al. 2017 Sol. Energy Mater. Sol. Cells 160 257
[12] Liang G X, Zheng Z H, Fan P et al. 2018 Sol. Energy Mater. Sol. Cells 174 263
[13] Hutter O S, Phillips L J, Durose K and Major J D 2018 Sol. Energy Mater. Sol. Cells 188 177
[14] Li D B, Yin X, Grice C R et al. 2018 Nano Energy 49 346
[15] Ngo T T, Chavhan S, Kosta I et al. 2014 ACS Appl. Mater. & Interfaces 6 2836
[16] Choi Y C and Il S 2015 Adv. Funct. Mater. 25 2892
[17] Choi Y C, Lee D U, Noh J H, Kim E K and Il S 2014 Adv. Funct. Mater. 24 3587
[18] Choi Y C, Lee Y H, Im S H et al. 2014 Adv. Funct. Mater. 4 1301680
[19] Wang W, Wang X, Chen G et al. 2018 Sol. RRL 2 1800208
[20] Shi X, Zhang X, Tian Y, Shen C, Wang C and Gao H J 2012 Appl. Surf. Sci. 258 2169
[21] Tang R, Wang X, Lian W et al. 2020 Nat. Energy 5 587
[22] Messina S, Nair M T S and Nair P K 2009 J. Electrochem. Soc. 156 H327
[23] Leng M, Luo M, Chen C, Qin S et al. 2014 Appl. Phys. Lett. 105 083905
[24] Li Z, Liang X, Li G, Liu H et al. 2019 Nat. Commun. 10 125
[25] Shockley W and Queisser H J 1961 J. Appl. Phys. 32 510
[26] Zhang L, Li Y, Li C et al. 2017 ACS Nano 11 12753
[27] Polman A, Knight M, Garnett E C, Ehrler B and Sinke W C 2016 Science 352 aad4424
[28] Li G, Li Z, Liang X et al. 2019 ACS Appl. Mater. & Interfaces 11 828
[29] Wu C, Jiang C, Wang X et al. 2019 ACS Appl. Mater. & Interfaces 11 3207
[30] Wang L, Li D B, Li K et al. 2017 Nat. Energy 2 17046
[31] Chen C, Zhao Y, Lu S et al. 2017 Adv. Energy Mater. 7 1700866
[32] Lu S, Zhao Y, Chen C, Zhou Y et al. 2018 Adv. Electron. Mater. 4 1700329
[33] Mihailetchi V D, Wildeman J and Blom P W M 2005 Phys. Rev. Lett. 94 126602
[34] Koster L J A, Mihailetchi V D, Xie H and Blom P W M 2005 Appl. Phys. Lett. 87 203502
[35] Chu T Y and Song O K 2007 Appl. Phys. Lett. 90 203512
[36] Malliaras G G, Shen Y and Dunlap D H 2001 Appl. Phys. Lett. 79 2582