High-performance Dye-sensitized Solar Cells Research Articles

Rational Design of Broadly Absorbing Boron Dipyrromethene-Carbazole Dyads for Dye-Sensitized Solar Cells: A DFT Study.

Structure engineering of boron dipyrromethene (BODIPY) organic dye, to increase its light-harvesting efficiency in dye-sensitized solar cells, has been the subject of rigorous research recently. Herein, we report on the rational designing of BODIPY-carbazole (D-π-A-A) dyads using density functional theory (DFT). The structure of BODIPY-carbazole was first modified by substituting an electron-donating −N(CH3)2 group at the electron-rich carbazole moiety, and two electron-accepting −COOH groups at the BODIPY core. The DFT calculations showed a significant lowering of the band gap from 2.9 eV (pristine BODIPY-carbazole dyad) to 1.87 eV (modified BODIPY-carbazole dyad). Further modification was demonstrated by the incorporation of heterocyclic rings such as thiophene (denoted as D1T), furan (D1F), and phosphole (D1P) into BODIPY-carbazole moiety, which red-shifted the light absorption spectra and consequently improved the light-harvesting efficiency of the dyes. The interactions at the dye/semiconductor interface were studied by employing their bridged-bidentate adsorption models over the titanium dioxide (TiO2)38 nanocluster. Results suggested that the electrons can be efficiently injected from the lowest unoccupied molecular orbital (LUMO) of dyes into the conduction band of TiO2. Among the three dyads, D1P exhibited superior photovoltaic performance with a maximum power conversion efficiency of 13.50%, a short-circuit current density (Jsc) of 27.2 mA·cm–2, and an open-circuit voltage (Voc) of 731 mV. The structurally configured new D1P dye can be used as a potential alternative photosensitizer for high-performance dye-sensitized solar cells.

Research Insights and Challenges of Secondary School Energy Education: A Dye-Sensitized Solar Cells Case Study

The research achievements of a university chemistry lab regarding dye-sensitized solar cells (DSSCs) were transformed into a high school hands-on course by simplifying the experimental steps and equipment. Our research methodology was action research. We verified the DSSC course step by step. First, 10 members of a high school science study club helped to revise the course over a school semester. A questionnaire survey revealed that all students agreed that the course increased their understanding of DSSCs and solar cells. Second, 35 students were enrolled in a 10th-grade elective energy course to study the revised DSSC topics for 3 weeks. A five-point Likert scale was used to collect students’ feedback, and students reported looking forward to making their own high-performance DSSC modules (4.60) and stated that being able to make their own solar cell was a great accomplishment (4.49). Third, the course was implemented at a junior high school science camp, and the 37 participating students were all able to complete the hands-on experiment. In the questionnaire survey, the students expressed that they enjoyed learning about scientific principles through a hands-on approach (4.59). Fourth, most of the 12 schoolteachers who voluntarily participated in the DSSC workshop agreed that integrating DSSC activity into school courses would be conducive to multidisciplinary learning. This course could facilitate participants’ self-evaluations in science knowledge, experimental skills, learning motivations, and positive attitudes toward sustainability.

D-π-A-structured organic sensitizers with π-extended auxiliary acceptor units for high-performance dye-sensitized solar cells

Two new D-π-A-structured dyes (SGT-160 and SGT-161) with the extension of π-conjugation in the acceptor unit have been designed and synthesized to modulate LUMO energy levels and to investigate the photophysical and electrochemical properties as well as cell performances. Based on a reference dye of SGT-130 as a platform of donor-π-bridge-BTD-phenyl-acceptor sensitizers, ethynylphenylene (T-Ph) and 2-ethynylthiophene (T-Th) moieties as an auxiliary π-spacer were introduced to replace the traditional phenylene (Ph) moiety for SGT-160 and SGT-161, respectively. It was found that the insertion of an additional ethynyl moiety into the BTD-Ph acceptor unit significantly enhanced the light-harvesting capability by extending the absorption bands and intensifying the molar absorptivity. Moreover, the π-extension in the acceptor part was beneficial for stabilizing the LUMO energy levels. The density functional theory (DFT) calculations and the partial density of states (PDOS) suggest that the variation of acceptor units affects the electronic transition between the major orbitals of the dyes. As a result, dye-sensitized solar cells (DSSCs) based on SGT-160 with a chenodeoxycholic acid (CDCA) co-adsorbent exhibited high power conversion efficiencies (PCEs) of 10.28%, while DSSCs based on SGT-161 and SGT-130 showed moderate PCEs of 8.05% and 10.06%, respectively.

Highly active MoTe2/g-C3N4 thin films-based Pt-free counter electrode for high-performance dye-sensitized solar cells

Highly active MoTe2/g-C3N4 thin films-based Pt-free counter electrode for high-performance dye-sensitized solar cells

Effect of low grain boundary crystallization Cu2ZnSnSxSe4−x counter electrode on the performance of dye-sensitized solar cells

The high surface area of porous Cu2ZnSnSxSe4−x (CZTSSe) counter electrodes (CEs) was commonly used for dye-sensitized solar cells (DSCs), because it can retard electron transport processes and form high quality crystallized film. Herein, we introduced a facile method to prepare CZTSSe film with bulk large-grained crystal by vacuum fast processing (VFP), which beneficial to form oriented crystalline film and reduce grain the film boundaries. Thus, performances of the DSCs devices showed an outstanding PCE of 8.3% with Voc, Jsc and fill factor of 0.729 V, 16.9 mA·cm−2, and 67.4%, respectively. With conducting spectral characterization and electrochemical techniques, it was found that the accelerating charge transfer speed and superior electrocatalytic activities contribute the majority part to DSCs photovoltaic performances. Furthermore, under AM1.5 illumination at 45 °C, the DSCs devices showed good stability and retained over 94% of its initial performance for 1000 h light soaking, indicating of their general applicability in fabricating high-performance DSCs.

Double-layer novel zinc porphyrin based on axial coordination self-assembly for dye-sensitized solar cells

Porphyrin sensitizers have attracted great attention due to their admirable performance in dye-sensitized solar cell (DSSC). In this work, three antenna zinc porphyrins ZnPi (i = 1–3) and anchored porphyrin ZnPA have been designed, synthesized, and characterized. The antenna molecules ZnPi adhere on to the anchored porphyrin ZnPA via metal–ligand axial coordination self-assembly, and then the ZnPA bonding to nanostructured TiO2 to prepared ZnPi(i = 1–3)-ZnPA based DSSCs. Optical performance analysis showed that the devices based on self-assemblies exhibited obviously enhanced light-harvesting ability than the monomer anchor molecule ZnPA. The photovoltaic results showed that, compared with the ZnPA-sensitized solar cell, the ZnPi(i = 1–3)-ZnPA-sensitized solar cells have higher short - circuit photocurrent density (Jsc). However, the open circuit voltage (Voc) of the self-assembled porphyrin-sensitized solar cells are lower than the ZnPA-sensitized solar cell, this is because of the increase of charge recombination rate of the self-assembled porphyrin-sensitized solar cells on the electrode. As a result, the devices based ZnPi (i = 1–3)-ZnPA exhibited enhanced photoelectric conversion efficiency (PCE) than monomer ZnPA-sensitized solar cell. Especially for the ZnP3-ZnPA-sensitized solar cell with a optimal PCE is 3.44%, indicating that the trifluoromethyl substituent of the antenna molecule ZnP3 porphyrin was a more suitable group. Additionally, density functional theory (DFT) calculations are used to further verify the test results of the assembled sensitized solar cells. Therefore, our new method, metal-ligand self-assembly strategy provides new ideas for the high-performance DSSC.

Composites of Vanadium (III) Oxide (V2O3) Incorporating with Amorphous C as Pt-Free Counter Electrodes for Low-Cost and High-Performance Dye-Sensitized Solar Cells.

To replace precious Pt-based counter electrodes (CEs) with a low-cost Pt-free catalyst of CEs is still a motivating hotspot to decrease the fabrication cost of dye-sensitized solar cells (DSSCs). Herein, four different V2O3@C composite catalysts were synthesized by pyrolysis of a precursor under N2 flow at 1100 °C and further served as catalytic materials of CEs for the encapsulation of DSSCs. The precursors of V2O3@C composites have been prepared via a sol–gel method using different proportions of V2O5 with soluble starch in a H2O2 solution. Power conversion efficiencies (PCEs) of 3.59, 4.79, 5.15, and 5.06% were obtained from different V2O3@C composites, with soluble starch-to-V2O5 mass ratios (S/V) of 1:2, 1:1, 2:1, and 4:1, respectively, as CEs to reduce iodide/triiodide in DSSCs. The improvement of electrode performance is due to the combined effects on the increased specific surface area and the enhanced conductivity of V2O3@C composite catalysts.

Structural Engineering of Organic D-A-π-A Dyes Incorporated with a Dibutyl-Fluorene Moiety for High-Performance Dye-Sensitized Solar Cells.

Structural engineering of the light-harvesting dyes employed in DSSCs (dye-sensitized solar cells) with a systematic choice of the electron-donating and -accepting groups as well as the π-bridge allows the (photo)physical properties of dyes to match the criteria needed for improving the DSSC efficiency. Herein, we report an effective approach of molecular engineering of DSSC sensitizers, aiming to gain insights on the configurational impact of the fluorenyl unit on the optoelectronic properties and photovoltaic performance of DSSCs. Five new organic dyes (GZ116, GZ126, GZ129, MA1116, and MA1118) with a D-A-π-A framework integrated with a fluorenyl moiety were designed and synthesized for DSSCs. The fluorenyl unit is configured as part of the π-spacer for the GZ series, whereas it connected on the electron-deficient quinoxaline motif for the MA series. The devices fabricated from the MA1116 sensitizer produced the best performance under standard AM 1.5 G solar conditions as well as dim-light (300-6000 lx) illumination. The devices fabricated from MA1116 displayed a PCE of 8.68% (Jsc = 15.00 mA cm-2, Voc = 0.82 V, and FF = 0.71) under 1 sun and 26.81% (Jsc = 0.93 mA cm-2, Voc = 0.68 V, and FF = 0.76) under 6000 lx illumination. The device efficiency based on dye MA1116 under 1 sun outperformed that based on the standard N719 dye, whereas a comparable performance between devices based on MA1116 and N719 was achieved under dim-light conditions. A combination of enhancing the charge separation, suppressing dye aggregation, and providing better insulation that prevents the oxidized redox mediator from approaching the TiO2 surface all contribute to the superior performance of DSSCs fabricated based on these light-harvesting dyes. The judicious integration of the fluorenyl unit in a D-A-π-A-based DSSC would be a promising strategy to boost the device performance.

Design and fabrication of Pt-free FeNi2S4/rGO hybrid composite thin films counter electrode for high-performance dye-sensitized solar cells

In this work, we synthesized FeNi2S4/rGO composites as Pt-free counter electrode (CE) by one step hydrothermal method. Complete investigations of phase evolutions by XRD patterns and TEM indicate spinel structure with nanosheets and nanospherical morphologies. The individual spherical-shaped nanoparticles (30–35 nm) of FeNi2S4 were exploited on the 2D ultrathin rGO nanosheets surface. This is useful for the provision of further electrolyte adsorptions and responsive electrocatalytic sites. The DSSC constructed with FeNi2S4/rGO hybrid composite CE showed a conversion efficiency of 9.98%, better than that by FeNi2S4 CE (4.87%) and also commercial Pt (6.21%). The outstanding efficiency of the FeNi2S4/rGO hybrid composite CE is even better than commercial Pt and is an effective alternative to Pt CE in the DSSCs.

Thiophene-fused carbazole derivative dyes for high-performance dye-sensitized solar cells

Two novel dyes that are similar in chemical structure, except for different donor units, AJ301 and AJ303 were synthesized, characterized and applied as sensitizers in dye-sensitized solar cells (DSSCs). Both dyes exhibited a wide absorption of visible sunlight. The introduction of fused rings on the donor unit of AJ303 presented an appropriate energy level, less recombination and longer electron lifetime to achieve a power conversion efficiency (PCE) of 10.2%, far above that achieved for AJ301 of 6.2% with a [Co(bpy) 3 ] 2+/3+ -based electrolyte under standard AM1.5G solar irradiation (100 mW cm −2 ). The DSSCs based on AJ303 and AJ301 with [Cu(tmby) 2 ] 2+/+ -based electrolyte showed a lower PCE of 8.2% and 5.4%, respectively. Therefore, the results indicated that the introduction of a fused-ring in the donor group is a meaningful synthetic strategy to improve the photovoltaic performance. • Two new metal-free dyes ( AJ301 , AJ303 ) were synthesized. • The thiophene-fused donor has more conducive to obtain higher conversion efficiency. • Both traditional cobalt electrolyte and burgeoning copper electrolyte are used in photovoltaic devices.

Effect of different dosage of gamma irradiation on quasi-solid-state conducting polymer electrolyte and its application as high performance dye-sensitized solar cells

ABSTRACT The nanocomposite polymer electrolyte [x (85 PVA: 10 PPy: 5 KI: I2:15 EC: 15MPII: 10 TiO2) for x = 5, 10, 15 Gy γ-ray irradiation] is prepared using the solution casting technique. Exposure of γ-ray irradiation enhanced the amorphous nature of the polymer electrolyte, is confirmed by XRD. The 15Gy γ-ray-irradiated nanocomposite polymer electrolyte has higher electrical conductivity and minimum activation energy (0.664 kJ mol−1). The EIS measurement reveals that the 15Gy γ-ray-irradiated nanocomposite polymer electrolyte incorporated DSSC shows lower Rct 1 and Rct 2 values at the counter electrode/electrolyte and photoanode/electrolyte interface, respectively. An outstanding performance is observed in the fabricated DSSCs using 15 Gy γ-ray-irradiated nanocomposite polymer electrolyte with a short circuit current density of 12.602 mA cm−2, an open-circuit voltage of 0.711 V, a fill factor of 0.535, and a photovoltaic conversion efficiency of 4.79% under the light intensity of 100 mW cm−2.

Electroactive and Sustainable Cu-MOF/PEDOT Composite Electrocatalysts for Multiple Redox Mediators and for High-Performance Dye-Sensitized Solar Cells

An electrically conductive Cu-MOF, {[Cu2(6-mercaptonicotinic acid)(6-mercaptonicotinate)]·NH4}n, was successfully electrodeposited on the conductive substrates via using poly(3,4-ethylenedioxythiophene) (PEDOT) as the binder. Multiple functionalities of the Cu-MOF microparticle within the Cu-MOF/PEDOT composite electrode were systematically vindicated as (1) releasing the cohesive strength among the PEDOT matrix, thus enhancing the film adhesion to substrate, (2) providing excellent intrinsic heterogeneous rate constant via lowering the reaction active energy, (3) supplying numerous active sites at the center or edges on its (-Cu-S-)n honeycomb-like planes, (4) facilitating the electron transfer through its two-dimensional (-Cu-S-)n plains, and (5) benefiting the penetration of the redox mediators through its porous frameworks. In multiple redox mediators (i.e., I-/I3-, cobalt(II/III)-complex, and copper(I/II)-complex), the composite Cu-MOF/PEDOT electrode exhibited superior electrocatalyst activity and kept almost 100% of its initial redox peak currents after continuous cyclic voltammetric scanning for 300 cycles. As a high-performance electrocatalyst for the counter electrode in dye-sensitized solar cells (DSSCs), the composite Cu-MOF/PEDOT electrode rendered its cell a decent solar-to-electricity conversion efficiency of up to 9.45% at 1 sun and 22.80% at room light illumination. Compared to the traditional platinum electrode (7.67%), the low-cost Cu-MOF/PEDOT composite electrode has great possibility to be used for various electrochemical devices and the Internet-of-things applications.

Efficient TiO2 nanoparticle-ruthenium sensitizers with high open-circuit voltage (Voc) for high-performance dye-sensitized solar cells

The study aims to characterize Ruthenium as a photosensitizer in Dye-Sensitized Solar Cells (DSSC). Samples are made in the structure of the working electrode pair Sandwich and the opponent electrode. Sample absorbance test using UV-Visible LAMBDA 25 spectrophotometer and test current and voltage characterization (I-V) using Keithley 2602A. The results of the study showed that the maximum absorbance in the high dye ruthenium appeared at the two peaks at 448 nm and 580 nm. While I-V curve measurements showed great efficiency that resulted in ruthenium dye with concentrations of 0.1, 0.5, and 1 in a row were 0, 12%, 0.186%, and 0.26%. These results show that higher concentrations of ruthenium dye can increase the value of the resulting efficiency.

Green Fluorine-Free Synthesis of Hollow Rectangular Prism-like TiO2 Mesocrystals with Exposed {001} Facets for High-Performance Dye-Sensitized Solar Cells

In this work, the hollow rectangular prism-like TiO2 (HRP-TiO2) mesocrystals with exposed {001} facets were synthesized via an in-situ hydrothermal process without introducing any additional hydrof...

Well-dispersed Te-doped mesoporous carbons as Pt-free counter electrodes for high-performance dye-sensitized solar cells

A tellurium-doped carbon nanomaterial (Te-MC(P)) was newly developed by the soft-templated carbonization of the PAN-b-PBA copolymer with poly(3-hexyltellurophene). Te-MC(P) was characterized with various characterization methods, including the nitrogen sorption isotherm measurement (BET), X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDS), which reveal that the Te atoms are homogeneously dispersed in the three-dimensional hierarchical, graphite-like mesoporous carbon matrix with a Te doping level of 0.27 atom %. Based on the characterization results, the electrocatalytic ability of Te-MC(P) was evaluated by using a symmetrical dummy cell test with both Co(bpy)32+/3+ (bpy = 2,2'-bipyridine) and I-/I3- redox electrolytes as counter electrodes (CEs). The Te-MC(P) CEs showed remarkably lower charge-transfer resistance (Rct) values by approximately 10 times in the electrochemical impedance spectroscopy (EIS) measurement, compared to the counterpart platinum (Pt) and the tellurium-based material (Te-MC(A)), prepared with a telluric acid precursor that has a lower Te doping level of 0.15 at%. As a result, the excellent electrocatalytic ability of Te-MC(P) resulted in the improvement of photovoltaic performance. The power conversion efficiencies (PCEs) of Te-MC(P)-based dye-sensitized solar cells (DSSCs) were 12.69% for the Co(bpy)32+/3+ redox electrolyte with the SGT-021 porphyrin dye and 9.73% for the I-/I3- redox electrolyte with the N719 ruthenium dye. Furthermore, Te- MC(P) CEs exhibited remarkable electrochemical stability in the two redox electrolytes. These results could suggest that the Te-MC(P) CE is one of the best promising alternatives to Pt CEs as a low-cost, highly stable and efficient electrocatalytic CE for practical applications.

Light-Absorbing Pyridine Derivative as a New Electrolyte Additive for Developing Efficient Porphyrin Dye-Sensitized Solar Cells

To fabricate efficient dye-sensitized solar cells (DSSCs), 4-tert-butylpyridine (TBP) is commonly used as an additive in the electrolytes for improving the photovoltages (VOC). However, TBP cannot play a positive role in improving the photocurrent (JSC) because of the lack of absorption in the visible-wavelength range. We herein report a light-absorbing pyridine derivative N1 as an additive for the axial coordination with porphyrin dyes. N1 was synthesized by introducing a (bis(4-methoxyphenyl)amino)anthryl moiety into the para-position of pyridine via an acetylene bridge, and porphyrin dye XW64 containing meso-3,5-disubstituted phenyl groups was synthesized considering that the meta-substituted phenyl groups may induce weaker steric hindrance with the axial pyridyl ligand, as compared with wrapped and strapped porphyrin dyes. Thus, N1 was used as an electrolyte additive together with TBP. When optimized concentrations of 6 mM N1 and 0.5 M TBP were used for fabricating DSSCs based on XW64, enhanced photovoltaic performance was achieved, with JSC, VOC, and efficiency of 15.65 mA·cm-2, 0.701 V, and 7.35%, respectively, superior to those of the corresponding DSSCs without using the additives (JSC = 14.86 mA·cm-2, VOC = 0.599 V, and efficiency = 5.94%). The enhancement of JSC can be ascribed to the improved light-harvesting ability induced by the axially coordinated N1. Furthermore, the two additives also can be used to fabricate efficient solar cells based on the wrapped porphyrin dye XW42, achieving high efficiency of 10.3%, indicative of their general applicability in fabricating high-performance DSSCs. These results indicate that the simultaneous employment of the traditional TBP additive and a pyridyl ligand with light-harvesting ability in the electrolyte for the axial coordination to a porphyrin dye is a promising approach for developing efficient DSSCs.

Dye-sensitized solar cells (DSSCs) as a potential photovoltaic technology based on La2MoO6/bio-carbon hybrid composite photoanodes with ~12.5% efficiency

In this work, series of bio-carbon (BC) activated La2MoO6 nanoparticles were prepared by a traditional hydrothermal method. The La2MoO6 nanoparticles are composited with bio-graphene to serve as a low-cost electrode to improve photovoltaic performance for dye-sensitized solar cells (DSSCs). The structural, morphological, optical and textural properties of the electrode samples were analyzed by using XRD, SEM, TEM, Raman, UV, PL and BET analysis. The La2MoO6/BC composite sample exhibits higher specific surface area (102.6 m2g−1) and larger total pore diameter (40.5 nm), compared with pure La2MoO6 (78.9 m2g−1 and 28.3 nm, correspondingly). The higher specific surface area provides more catalytic sites; thus, the DSSC assembled with a La2MoO6/BC composite electrode deliver power conversion efficiency (PCE) of 12.5%. This could be due to the narrowing of the band gap which prevents the recombination process of electron-hole pair. Moreover, the EIS analysis illustrates that La2MoO6/BC composite show high electron transfer efficiency and long life time than bare La2MoO6 electrode sample. This work provides new insights into the utilization of La2MoO6/BC based photoanode materials for high performance DSSC based applications.

High Performance Dye-Sensitized Solar Cells Based on Electrospun MoS2-Carbon Nanofiber Composite Counter Electrode

MoS2-carbon nanofiber composites were prepared via electrospun technique with ammonium thiomolybdate(VI) and PVP. The effects of thermal pretreatment on the morphology of material were studied. The results demonstate that the composite nanofiber with pretreatment shows a uniform diameter and lots of small size MoS2 particles inside with porous structure. When the composites was used as counter electrodes in dye-sensitized solar cell, a maximum efficiency of 5.7% has been achieved due to the combination of electrical conductivity and catalysis ability from MoS2-carbon nanofiber composites.

Fluorine-free synthesis of reduced graphene oxide modified anatase TiO2 nanoflowers photoanode with highly exposed {0 0 1} facets for high performance dye-sensitized solar cell

A facile, fluorine-free and non-toxic one-pot solvothermal technique was adopted to synthesis TiO2 nanoflowers with anatase phase having 98% highly exposed {001} facets (TiO2 {001} NFs). The morphology, grain size and crystallinity of pure TiO2 {001} NFs and reduced graphene oxide (RGO) sheets modified TiO2 {001} NFs (RGO-TiO2 {001} NFs) were inspected by diffuse reflectance spectroscopy (DRS), X-ray diffractometry (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). TEM images showed the development of anatase TiO2 {001} NFs with high crystallinity and uniform shape. The influence of RGO on the performance of the TiO2 {001} NFs as a photoanode material in dye-sensitized solar cell (DSSC) was examined. High energy conversion efficiency (ɳ) was observed for the DSSC based on a photoanode made of RGO-TiO2 {001} NFs when compared to DSSCs based on photoanodes fabricated using pure TiO2 {001} NFs and commercial Degussa P25 TiO2, which exhibited η of 6.78, 4.59 and 2.71%, respectively. The improved performance of the DSSC based on a photoanode composed of RGO-TiO2 {001} NFs was due to its good crystallinity, high dye intake and enhanced light-harvesting properties. Moreover, the presence of RGO greatly hindered the recombination of photogenerated electrons and increased their lifespan. This work discloses a novel efficient photoanode design for improving performance of the DSSCs.

Current Progress in Solid-State Electrolytes for Dye-Sensitized Solar Cells: A Mini-Review

Low-cost and high-performance dye-sensitized solar cells (DSSCs) are considered promising candidates for commercial application. As one of the crucial components, electrolytes are considered the limiting factor for long-term DSSC stability. As alternative materials, solid-state electrolytes have been used in DSSCs, which may solve the problem of liquid electrolytes, such as leakage and volatilization. In this review, we define solid-state electrolytes as inorganic hole transport materials (HTMs), organic HTMs, ionic conductive polymer electrolytes, and ionic liquid polymer electrolytes according to the different types of carriers and summarize the latest development trends of these electrolytes. We discuss in detail the mechanism of solid-state dye-sensitized solar cells (ssDSSCs), including the hole transfer process at the dye/hole-conductor interface and factors that reduce the efficiency of ssDSSCs, and summarize several methods to improve the efficiency and long-term stability of ssDSSCs. These may facilitate the research and development of electrolytes for ssDSSCs.