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Colloidal quantum dots (CQDs) are promising materials for building next-generation solution-processed, high-performance, and low-cost optoelectronic devices. The photoelectric properties of the resulting films are not only determined by the intrinsic characteristics of the CQDs but are also significantly affected by the electrical coupling between them. However, enhancing the electrical coupling in CQD-based films is still a big challenge. In this work, a two-step ligand exchange strategy has been conducted to solve the above issue, where the InZnP@PbS CQDs have been used as the case. First, the Meerwein salt (Et 3 OBF 4) solution in N, N -dimethylformamide (DMF) has been employed to peel off the native ligands that are strongly capped on the surface of oil-soluble CQDs, resulting in a neat surface. Second, iodide ions are linked to the neat surface of the CQDs to narrow the distance between them and passivate their defects, establishing strong electrical coupling. Transient surface photovoltage (TSPV) and photo-conductance tests confirm that the resulting InZnP@PbS–I CQDs films possess good photoelectric properties and stability. In the fabricated solid-state solar cells, 3.1 % of the photoelectric conversion efficiency (PCE) has been achieved under 1 sun. The current results are outstanding for III-V group CQD-based all solid-state solar cells. • Fabricating the III-V group InZnP CQDs coated with PbS shell. • Two-step exchanges the ligands that strongly capped on the surface of CQDs. • Establishing strong electrical coupling between the InZnP@PbS CQDs in films. • Boosting the performance of InP CQD-based solid-state solar cells. [ABSTRACT FROM AUTHOR]

A high-conductivity thiocyanate ionic liquid (EMIMSCN) was introduced into perovskite solar cells for the first time. The high conductivity of EMIMSCN ensures an adequate supply of free SCN− anions and EMIM+ cations, so as to multifunctionally passivate the I vacancy and Pb–I antisite defects and realize an optimized interfacial energy level. Consequently, the devices with EMIMSCN treatment achieve a high PCE of 22.55% with substantial enhancement in stability. This simple and efficient strategy provides new insights into the selection of passivation agents for efficient and stable PSCs. [ABSTRACT FROM AUTHOR]

Defect passivation via post‐treatment of perovskite films is an effective method to fabricate high‐performance perovskite solar cells (PSCs). However, the passivation durability is still an issue due to the weak and vulnerable bonding between passivating functional groups and perovskite defect sites. Here we propose a cholesterol derivative self‐assembly strategy to construct crosslinked and compact membranes throughout perovskite films. These supramolecular membranes act as a robust protection layer against harsh operational conditions while providing effective passivation of defects from surface toward inner grain boundaries. The resultant PSCs exhibit a power conversion efficiency of 23.34 % with an impressive open‐circuit voltage of 1.164 eV. The unencapsulated devices retain 92 % of their initial efficiencies after 1600 h of storage under ambient conditions, and remain almost unchanged after heating at 85 °C for 500 h in a nitrogen atmosphere, showing significantly improved stability. [ABSTRACT FROM AUTHOR]

Although hybrid solar cells take advantages of both inorganic and organic semiconductors for high performance, there have not been comparably photoelectric conversion efficiencies as expected from this kind of solar cells till now. The photoelectric response behavior of inorganic/organic hybrid solar cells has been explained on the theory of inorganic solar cells, but the distinctive wavelength dependent photoelectric character of organic semiconductors has not been well considered. In this work, Ag 2 S/organic bulk heterojunction solar cell devices were designed and fabricated in-situ on indium tin oxide (ITO) based on the direct metal surface elemental reaction (DMSER) method, to understand the corresponding photoinduced charge carrier dynamics under different wavelength light. The commonly used small molecule Spiro-OMeTAD and polymeric PTB7-Th were selected as the organic components of the fabricated solar cells. In Ag 2 S/Spiro-OMeTAD, Ag 2 S donated the charge carriers and controlled the photoinduced charge carrier dynamics of the devices at both 355 nm and 532 nm lights. Under 532 nm light, the PTB7-Th acted as hole transport materials (HTM) rather than charge carrier donor. These results indicated that hybrid thin films without wavelength dependent charge carrier dynamics is preferred for high performance solar cells. [ABSTRACT FROM AUTHOR]

The development of new chemical methods to prepare large area perovskite thin film solar cells is desirable for potential future industrial applications. In this paper, a novel fabrication of perovskite CH 3 NH 3 PbI 3 thin films based on direct metal surface elemental reaction (DMSER) method in an ambient atmosphere is discussed. The as-prepared CH 3 NH 3 PbI 3 thin films are highly pure and crystalline. Consequent Transient photovoltaic (TPV) tests were conducted and show that these thin films have a long minority carrier lifetime as good as the perovskite thin films obtained via common two-step method from the literature. Although there have been many studies that have developed perovskite solar cells (PSCs) during the past five years, the current study is the first report using elemental Pb as a precursor to fabricate perovskite solar cells, which were found to be relatively stable upon storage without encapsulation in glove box for more than 200 days. This Pb-initiated in-situ reaction allows for the fabrication of large area and uniform perovskite thin films. For example, in our preliminary studies, we have fabricated large area solar cell device samples (1.10 ± 0.05 cm 2 ) and have evaluated their photovoltaic performance under standard conditions (AM 1.5, 100 mW cm −2 ). [ABSTRACT FROM AUTHOR]

[Display omitted] • Surface chemistry of CdSe CQDs influences the charge carrier transfer. • Photoinduced hole transport plays the key role in CdSe CQDs solid solar cells. • PbS helps the photoinduced hole transport in CdSe CQDs solid solar cells. Solar cells based on colloidal quantum dots (CQDs) have achieved great progress in recent years. However, the stable and high performance all solid solar cells using CQDs as light absorber are numbered till now. In this work, CdSe CQDs solid state solar cells have been fabricated as a case for revealing the reasons of low photoelectric conversion efficiency. It finds that the inefficient photoinduced hole transport block the improvement of the photoelectric performance. For facilitating the hole transport, a thin PbS interlayer has been fitted between the CQDs and hole transport layer, and as a result the photocurrent receives about 7.8 times increase in the devices constructed with 5.1 nm CQDs. Finally, a 1.29% of PCE is obtained from the solar cells with FTO/TiO 2 /CdSe CQDs/PbS/ Sprio-MeOTAD/Ag structure. [ABSTRACT FROM AUTHOR]

The III-V group colloidal quantum dots (CQDs) have been successfully synthesized with stable and low-cost chemical reagents recently, but they are rarely used for solid state solar cells due to the poor charge carrier transfer in solid films. In this work, the surface of InZnP (Zn doped InP) CQDs has been reconstructed with PbS via a chemical engineering strategy. Comparing with InZnP CQDs, the long carbon chain ligands capped on the InZnP@PbS CQDs surface can be easily exchanged with small molecules. By capping the mercaptopropionic acid (MPA) onto the InZnP@PbS CQDs surface, the electrical coupling between the InZnP@PbS CQDs has been established, and the photoinduced charge carrier transfer has been significantly enhanced. Based on the above CQDs, solid state solar cell devices are assembled, achieving about 1.5% of power conversion efficiency (PCE). The photoelectric performances of the fabricated solar cells almost do not decay after 150 days storage. Current work may provide a new way for III-V group CQDs application in solution-processed optoelectronics. • InZnP@PbS CQDs have been successfully synthesized via ion exchange strategy. • InZnP@PbS CQDs possess enhanced charge carrier transfer character. • InZnP@PbS CQDs based solid state solar cells have been constructed. [ABSTRACT FROM AUTHOR]

Solar cells devices based on inorganic/polymer heterojunction can be a possible solution to harvest solar energy and convert to electric energy with high efficiency through a cost-effective fabrication. The solution-process method can be easily used to produce large area devices. Moreover, due to the intrinsic different charge separation, diffusion or recombination in various semiconductors, the interfaces between each component may strongly influence the inorganic/polymer heterojunction performance. Here we prepared a n-type Ag 3 CuS 2 (Eg = 1.25 eV) nanostructured film through a room-temperature element reaction process, which was confirmed as direct bandgap semiconductor through density function theory simulation. This Ag 3 CuS 2 film was spin-coated with an organic semiconducting poly(3-hexythiophene) (P3HT) or polythieno[3,4-b]-thiophene-co-benzodithiophene (PTB7) film, which formed an inorganic/polymer heterojunction. After constructing it to a solar cell device, the power conversion efficiencies of 0.79% and 0.31% were achieved with simulated solar illumination on Ag 3 CuS 2 /P3HT and Ag 3 CuS 2 /PTB7, respectively. A possible mechanism was discussed and we showed the charge separation at interface of inorganic and polymer semiconductors played an important role. [ABSTRACT FROM AUTHOR]

CdS nanostructured thin films have been directly fabricated on indium-tin oxide (ITO) glass substrates through a one-step solvothermal process involving a cadmium nanocrystal layer and sulfur powder in N,N-dimethyl formamide (DMF). Poly(3-hexylthiophene) (P3HT) was then infiltrated into the CdS framework. The CdS film and the CdS–P3HT hybrid film were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), photoluminescence spectroscopy (PL) and UV-vis spectroscopy. CdS–P3HT hybrid film exhibited a wider absorption in the solar spectrum and stronger photo-current response and external quantum efficiency than a pure CdS and P3HT film. Hybrid solar cell devices have been constructed based on the CdS–P3HT hybrid film with structure ITO–CdS–P3HT–Au. The effects of sulfur sources, solvent and thickness of elemental cadmium films on the photovoltaic performance of CdS–P3HT hybrid solar cells were assessed. [ABSTRACT FROM AUTHOR]

• CdS under-layer reduces the recombination at Ag 2 S/FTO interface. • Photoinduced charge carrier dynamics of FTO/CdS/Ag 2 S has been studied. • CdS under-layer raise 52% PCE of Ag 2 S solar cell. [Display omitted] The recombination of photoinduced charge carriers is detrimental to the photovoltaic performance of solar cells. In this work, we used CdS as an under-layer to reduce the recombination of photoinduced charge carriers at the Ag 2 S/FTO (F-doped SnO 2) interface. The CdS under-layer was deposited onto an FTO substrate using a facile chemical bath deposition (CBD) method. By controlling the thickness of the CdS film between Ag 2 S and FTO, the recombination of photoinduced charge carriers was successfully suppressed. The effect of the CdS under-layer on the charge carrier recombination was carefully evaluated by transient surface photovoltage (TSPV) measurements, electrochemical impedance spectroscopy (EIS) and a photoelectrochemical method. The power conversion efficiency (PCE) of solar cell devices with a 40 nm CdS under-layer is 1.16%, which is ~52% enhancement compared to those of FTO/Ag 2 S-based solar cell devices. Our work may provide a useful strategy to suppress photoinduced charge carrier recombination at the electrode and absorber semiconductor interface. [ABSTRACT FROM AUTHOR]

An directly purifiable approach is developed to pre-oxidize the spiro-OMeTAD by using the Cobalt (III) trifluoride (CoF 3) as a p -type dopant. The unreacted dopant, by-products (CoF 2) and Li sediment is insoluble and can be readily removed by filtering the mixture. The new pre-oxidizing technique leads to an efficient and stable perovskite solar cell with an efficiency exceeding 23%. [Display omitted] • CoF 3 is developed as a p -type dopant for the efficient pre-oxidation of spiro-OMeTAD. • The oxidation reaction occurs at the solid/liquid interface. • The residual reactant and by-products are readily removed by filtering. • Part of the detrimental Li+ can be precipitated out during the pre-oxidation process. • High efficiency of 23.05% is achieved for PSCs with improved stability. Spiro-OMeTAD so far remains the most popular material as the hole-transport layer (HTL) for efficient perovskite solar cells (PSCs). However, the residual dopant, by-products and the hygroscopic lithium salt that remained in the HTL are commonly harmful to the PSCs performance. We develop here a new approach to pre-oxidize the spiro-OMeTAD by using the Cobalt (III) trifluoride (CoF 3) as a p -type dopant. Both the CoF 3 and its reduced form (CoF 2) are insoluble in the spiro-OMeTAD:LiTFSI mixture and the oxidation reaction occurs at the solid/liquid interface. Therefore, the unreacted dopant and by-products (CoF 2) can be readily removed by filtering, leading to a purifiable pre-oxidation of spiro-OMeTAD and thus a high-quality HTL with improved conductivity and hole mobility. Additionally, part of detrimental Li+ ions can also be purified out of the spiro-OMeTAD solution in the form of LiF sediments, which improves the stability and reliability of the devices. The resulting PSC achieves an efficiency of 23.05% together with improved stability, maintaining 91% of its initial PCE after one month of storage in the atmosphere with 20–30% relative humidity. These findings provide a new strategy to dope HTL for efficient and stable PSCs. [ABSTRACT FROM AUTHOR]