Double Cascading Charge Transfer at Integrated Perovskite/Organic Bulk Heterojunctions for Extended Near-Infrared Photoresponse and Enhanced Photocurrent.

Nowadays, nearly 48.7% near-infrared (NIR) irradiation (>800 nm) of the full solar spectrum has actually not been fully utilized since the state-of-the-art perovskite film usually can only absorb the most UV-vis sunlight radiation. Herein, high efficiency integrated Cs0.15 FA0.85 PbI3 perovskite/organic bulk (PC61 BM:D18:Y6) heterojunction solar cells with enhanced low energy photon harvest until 931 nm and a high maintained open circuit voltage of 1.04 V is successfully obtained. In particular, the favorable double cascading charge transfer paths pave an interesting possibility to spatially separate electrons upon visible light excitation and holes upon NIR photon absorption simultaneously at interfaces, significantly suppressing non-radiative bimolecular recombination and reaching the photocurrent density as high as 27.48 mA cm-2 and power conversion efficiency of 20.31%. Besides, the strong hydrophobicity of the ternary organic film has effectively prevented ambient humidity penetration and improves the stability of the perovskite in the continuous aging test (humidity > 60%) compared with the control device. This work has opened a significantly new window to improve the NIR light harvest for next generation highly efficient solar cells with full spectrum response.

Lead-chelating hole-transport layers for efficient and stable perovskite minimodules.

The defective bottom interfaces of perovskites and hole-transport layers (HTLs) limit the performance of p-i-n structure perovskite solar cells. We report that the addition of lead chelation molecules into HTLs can strongly interact with lead(II) ion (Pb2+), resulting in a reduced amorphous region in perovskites near HTLs and a passivated perovskite bottom surface. The minimodule with an aperture area of 26.9 square centimeters has a power conversion efficiency (PCE) of 21.8% (stabilized at 21.1%) that is certified by the National Renewable Energy Laboratory (NREL), which corresponds to a minimal small-cell efficiency of 24.6% (stabilized 24.1%) throughout the module area. Small-area cells and large-area minimodules with lead chelation molecules in HTLs had a light soaking stability of 3010 and 2130 hours, respectively, at an efficiency loss of 10% from the initial value under 1-sun illumination and open-circuit voltage conditions.

Fine Emission Tuning from Near-Ultraviolet to Saturated Blue with Rationally Designed Carbene-Based [3 + 2 + 1] Iridium(III) Complexes.

We designed and synthesized a new class of six phosphorescent [3 + 2 + 1] iridium(III) complexes [(pbib)Ir(C^C)CN] bearing a tridentate 1,3-bis(1-butylimidazolin-2-ylidene) phenyl N-heterocyclic carbene (NHC)-based pincer ligand (pbib), bidentate imidazole-based NHC ligands (C^C), and a monodentate cyano group and investigated their photophysical, electrochemical, and thermal stabilities and electroluminescent properties. The extended π-conjugation of the imidazole-based C^C ligand is found to be the key to fine-tune the emission energies from ultraviolet blue (λ = 378 nm) to saturated blue (λ = 482 nm), as shown by electrochemical and photophysical studies, which is also revealed by the density functional theory (DFT) and time-dependent DFT calculations. Vacuum-deposited organic light-emitting diode devices have been fabricated with these newly synthesized emitters and exhibited the best external quantum efficiency of 6.4% and Commission International de L'Éclairage (CIE) coordinates of (0.163, 0.096), where the CIE y is very similar to the National Television System Committee standard blue CIE (x, y) coordinates of (0.149, 0.085). These results indicate that the novel [3 + 2 + 1] coordinated iridium(III) complexes [(pbib)Ir(C^C)CN], having a saturated blue emission, not only could alleviate the photodegradation of the emitters when compared to [(pbib)Ir(pmi)CN] but also provide new design strategies of saturated-blue-emitting iridium(III) complexes.

[Relationships between the molecular biomarkers and the clinicopathologic features and prognosis in endometrial carcinoma].

OBJECTIVE: To explore the relationships between the expressions of estrogen receptor (ER), progestin receptor (PR), phosphatase and tension homology deleted on chromosome ten (PTEN), p53, Ki-67 and the clinicopathologic features and prognosis in endometrial carcinoma. METHODS: The data of clinical characteristics, pathological types, histological grades, follow-ups and the expressions of molecular markers detected by immunohistochemistry, and collected from 200 patients with primary endometrial carcinoma, were analyzed. RESULTS: (1) In the cases of endometrial carcinoma, the expression rates of ER, PR, PTEN, p53 were 86.5%, 85.5%, 82.1%, and 49.2%, respectively. The expression level of Ki-67 in the tumor tissues was 46.9% ± 24.7%. (2) A negative correlation was observed between the gravidity and the expression of PR (r=-0.191, P=0.007). On the other hand, age and parturition time were in positive correlation with the expression of p53 (r=0.184, P=0.041; r=0.255, P=0.004). (3) The expression rates of ER, PR and p53 in the endometrioid carcinoma exhibited significant differences comparing with other types (P<0.01). (4) A negative correlation was found between the expression of ER and the FIGO staging (r=-0.176, P=0.013). The positive rate of ER in the cases with Stage I was higher than that in cases with Stage II and above (P=0.015). (5) A negative correlation was found between the histological grade and the expressions of ER and PR (r=-0.217, P=0.002; r= -0.317, P=0.000), however, a positive correlation was detected between the grade with the expressions of p53 and Ki-67 (r=0.327, P=0.000; r=0.465, P=0.000). Compared with the grade 3 tumors, the other grades exhibited significant different expression levels of ER, PR, p53, and Ki-67 (P<0.01). (6) A negative correlation was observed between the depth of myometrial invasion and the positive rate of ER (r=-0.142, P=0.047). There were statistically significant different expression rates of ER and PR between the cases whether the cancer invaded the deep myometrium or not (P<0.05). (7) Multivariate survival analysis showed that patients with PR (+) had longer overall survival than those with PR (-) (P=0.011). CONCLUSION: The immunohistochemical study of endometrium samples obtained from dilatation and curettage of uterine will be beneficial to the understanding of the clinicopathologic features of the endometrial carcinoma before the operation. The value of estimating the prognosis using the expressions of ER, PTEN, p53 and Ki-67 was negative, except for the expression of PR.

Poly(Ethylene Glycol) Diacrylate as the Passivation Layer for High-Performance Perovskite Solar Cells.

In the past decade, greatest effect has been paid on organic-inorganic halide perovskites for approaching high-performance perovskite solar cells (PSCs). It was found that severe surface-defect within the perovskite active layer restricted further boosting device performance of PSCs. Here, we report high-performance PSCs by utilization of an ultrathin solution-processed poly(ethylene glycol) diacrylate (PEGDA) layer to passivate the surface-defect within the perovskite thin film. Systematical studies demonstrate that the PEGDA-passivated perovskite thin film exhibit suppressed nonradiative recombination and trap density, as well as superior film morphology with a smoother surface, larger crystal size, and better crystallinity. Moreover, PSCs by the PEGDA-passivated perovskite thin film exhibit suppressed charge carrier recombination, reduced charge-transfer resistance, shorter charge carrier extraction time, and enlarged built-in potential. As a result, PSCs by the PEGDA-passivated perovskite thin film show a power conversion efficiency of over 21% and a photocurrent hysteresis index of 0.037. Moreover, unencapsulated PSCs by the PEGDA-passivated perovskite thin film possess over 10 day operational stability. All these results indicate that our approach provided a facile way to boost device performance of PSCs.

Suppressing Defects-Induced Nonradiative Recombination for Efficient Perovskite Solar Cells through Green Antisolvent Engineering.

Organic-inorganic hybrid perovskites have attracted considerable attention due to their superior optoelectronic properties. Traditional one-step solution-processed perovskites often suffer from defects-induced nonradiative recombination, which significantly hinders the improvement of device performance. Herein, treatment with green antisolvents for achieving high-quality perovskite films is reported. Compared to defects-filled ones, perovskite films by antisolvent treatment using methylamine bromide (MABr) in ethanol (MABr-Eth) not only enhances the resultant perovskite crystallinity with large grain size, but also passivates the surface defects. In this case, the engineering of MABr-Eth-treated perovskites suppressing defects-induced nonradiative recombination in perovskite solar cells (PSCs) is demonstrated. As a result, the fabricated inverted planar heterojunction device of ITO/PTAA/Cs0.15 FA0.85 PbI3 /PC61 BM/Phen-NADPO/Ag exhibits the best power conversion efficiency of 21.53%. Furthermore, the corresponding PSCs possess a better storage and light-soaking stability.

Bulk Heterojunction Perovskite Solar Cells Incorporated with Zn2SnO4 Nanoparticles as the Electron Acceptors.

Perovskite solar cells were developed very fast in the past decade, but hybrid perovskite materials with unbalanced charge carrier diffusion lengths were not fully addressed by either conventional or planar heterojunction device structures. In this study, high-performance perovskite solar cells with bulk heterojunction device structures where CH3NH3PbI2.55Br0.45 is blended with an n-type high-electron-mobility Zn2SnO4 nanoparticle as the photoactive layer are reported. Systematic studies indicate that the CH3NH3PbI2.55Br0.45:Zn2SnO4 bulk heterojunction thin film possesses enhanced and balanced charge carrier mobilities, superior film morphology with enlarged crystal sizes, and suppressed trap density. Photoluminescence and time-resolved photoluminescence studies further demonstrate that there is an efficient photoinduced charge carrier transfer between CH3NH3PbI2.55Br0.45 and Zn2SnO4 nanoparticles. Thus, bulk heterojunction perovskite solar cells by the CH3NH3PbI2.55Br0.45:Zn2SnO4 thin film exhibit over 21.07% power conversion efficiency, which is more than 12% enhancement as compared to that (18.74%) observed from planar heterojunction perovskite solar cells by the pristine CH3NH3PbI2.55Br0.45 thin film. Moreover, bulk heterojunction perovskite solar cells possess significantly suppressed photocurrent hysteresis, dramatically enhanced device stability, and reproducibility. All these results demonstrate that high-performance perovskite solar cells can be realized through bulk heterojunction device structures.

Efficient Perovskite Solar Cells through Suppressed Nonradiative Charge Carrier Recombination by a Processing Additive.

It has been reported that nonradiative charge carrier recombination in hybrid perovskite materials restricts the device performance of perovskite solar cells. In this study, we report efficient perovskite solar cells through suppressed nonradiative charge carrier recombination by a processing additive, aminopropanoic acid. It is found that aminopropanoic acid not only modulates the crystal growth processes but also minimizes the defects of CH3NH3PbI3 thin films. Moreover, the CH3NH3PbI3 thin films processed with the addition of aminopropanoic acid exhibit both enhanced photoluminescence and electroluminescence and elongated charge carrier lifetime, indicating that nonradiative charge carrier recombination within the CH3NH3PbI3 thin films is drastically suppressed. As a result, perovskite solar cells fabricated using the CH3NH3PbI3 thin films processed with the addition of aminopropanoic acid exhibit approximately 15% enhanced efficiency as compared with those made with pristine CH3NH3PbI3 thin films. All of these results demonstrate that our findings provide a facile way to improve the efficiency of perovskite solar cells.

Highly crystalline CsPbI2Br films for efficient perovskite solar cells via compositional engineering.

All-inorganic CsPbI2Br shows high thermal stability for promising application in perovskite solar cells (PSCs). The performance of PSCs is significantly affected by their morphology and crystallinity induced by compositional ratio, solvent/anti-solvent engineering and post thermal annealing. In this study, the compositional ratio effect of two precursors, PbI2 and CsBr, on the power conversion efficiency (PCE) of a device with ITO/SnO2/CsPbI2Br/Spiro-MeOTAD/Au structure was investigated. With the assistance of anti-solvent chlorobenzene, perovskite with a PbI2 : CsBr ratio of 1.05 : 1 showed a high quality thin film with higher crystallinity and larger grain size. In addition, the molar ratio of precursors PbI2 and CsBr improved the PCE of the PSCs, and the PSCs fabricated using the perovskite with an optimal ratio of PbI2 and CsBr exhibited a PCE of 13.34%.

A zwitterionic polymer as an interfacial layer for efficient and stable perovskite solar cells.

Perovskite solar cells have been rapidly developed in the past ten years. It was demonstrated that the interfacial layer plays an important role in device performance of perovskite solar cells. In this study, we report utilization of a photoinitiation-crosslinked zwitterionic polymer, namely dextran with carboxybetaine modified by methacrylate (Dex-CB-MA), as an interfacial layer to improve the film morphology of the CH3NH3PbI3 photoactive layer and the interfacial contact between the poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) hole extraction layer and CH3NH3PbI3 photoactive layer. It is found that the Dex-CB-MA thin layer forms a better band alignment between the PEDOT:PSS hole extraction layer and CH3NH3PbI3 photoactive layer, and improves the crystallization of the CH3NH3PbI3 photoactive layer, resulting in efficient charge carrier transport. As a result, perovskite solar cells with the PEDOT:PSS/Dex-CB-MA hole extraction layer exhibit more than 30% enhancement in efficiency and dramatically boosted stability as compared with that with the PEDOT:PSS hole extraction layer. Our studies provide an effective and facile way to fabricate stable perovskite solar cells with high power conversion efficiency.

Cesium-Doped Vanadium Oxide as the Hole Extraction Layer for Efficient Perovskite Solar Cells.

In this study, we report the utilization of low-temperature solution-processed Cs-doped VOX thin films as the hole extraction layers (HELs) in perovskite solar cells (PSCs). It is found that the VOX:yCs (where y is the mole ratio of Cs versus V and y = 0.1, 0.3, and 0.5) thin films possess better electrical conductivities than that of the pristine VOX thin film. As a result, the PSCs incorporated with the VOX:yCs HEL exhibit large fill factors and high short-circuit currents, with consequently high power conversion efficiencies, which is more than 30% enhancement as compared with pristine VOX HEL. Our studies provide a facial way to enhance the electrical conductivity of the hole extraction layer for boosting device performance of perovskite solar cells.

Efficient Perovskite Solar Cells with Reduced Photocurrent Hysteresis through Tuned Crystallinity of Hybrid Perovskite Thin Films.

Hybrid perovskite materials used for realization of efficient perovskite solar cells have drawn great attention in both academic and industrial sectors. It was reported that the crystallinity of hybrid thin-film perovskite materials plays an important role in device performance. In this study, we report a novel and simple method to tune the crystallinity of CH3NH3PbI3 thin film for device performance of perovskite solar cells. By employing tetraphenylphosphonium chloride on the top of PbI2 thin layer in the two-step perovskite deposition processes, the crystallinity of the resultant CH3NH3PbI3 thin film was tuned. As a result, perovskite solar cells by the CH3NH3PbI3 thin film with tuned crystallinity exhibit an enlarged open-circuit voltage and enhanced short-circuit current, thus boosted efficiency as well as reduced photocurrent hysteresis compared to pristine CH3NH3PbI3 thin film. These results indicate that our study provides a new simple way to boost device performance of perovskite solar cells through tuning the crystallinity of CH3NH3PbI3 thin film.

Modifying the Chemical Structure of a Porphyrin Small Molecule with Benzothiophene Groups for the Reproducible Fabrication of High Performance Solar Cells.

A porphyrin-based molecule DPPEZnP-BzTBO with bulky benzothiophene groups was designed and synthesized as an electron donor material for bulk heterojunction (BHJ) solar cells. The optimized devices under thermal annealing (TA) and then chloroform solvent vapor anneanling (SVA) for 80 s exhibited an outstanding power conversion efficiencie (PCE) of 9.08%. Contrasted with the smaller thienyl substituted analogues we reported previously, DPPEZnP-BzTBO-based BHJ solar cells exhibited a higher open circuit voltage due to the lower highest occupied molecular orbital energy level. The TA post-treatment of the active layers induced the formation of more crystallized components, and the subsequent SVA provided a driving force for the domain growth, resulting in more obvious phase segregation between the donor and the acceptor in nanoscale. Furthermore, the PCEs kept above 95% upon the further SVA treatment within the time range of 60 to 95 s probably because the bulky benzothiophene groups retard the too quick change of crystallinity, providing a wide processing window for the reproducible device fabrication.

Efficient Organic Solar Cells with Polymer-Small Molecule: Fullerene Ternary Active Layers.

In this study, we report organic solar cells (OSCs) fabricated by a polymer-small molecule: the fullerene ternary active layer. It is found that a significantly enhanced power conversion efficiency contributed to the enhanced short-circuit current density and fill factor (FF). Investigation of absorption spectra and external quantum efficiency spectra indicate that the enhancement in photocurrent originates from the improved light absorption attributed to the small molecule. Further investigations by grazing-incidence wide-angle X-ray scattering, transmission electron microscopy, and atomic force microscopy reveal that charge transport within the ternary active layer is facilitated by a reduced π-π distance between the adjacent polymer chains along the out-of-plane direction, good miscibilities between ternary components, and the rougher surface of the resultant thin film. As a result, the hole mobility of the polymer electron donor and electron mobility of the fullerene electron acceptor are considerably increased, resulting in enhanced FFs. Our studies provide a facile route to realize efficient OSCs.

Efficient Polymer Solar Cells by Lithium Sulfonated Polystyrene as a Charge Transport Interfacial Layer.

In this paper, we report the highly efficient bulk heterojunction (BHJ) polymer solar cells (PSCs) with an inverted device structure via utilizing an ultrathin layer of lithium sulfonated polystyrene (LiSPS) ionomer to reengineer the surface of the solution-processed zinc oxide (ZnO) electron extraction layer (EEL). The unique lithium-ionic conductive LiSPS contributes to enhanced electrical conductivity of the ZnO/LiSPS EEL, which not only facilitates charge extraction from the BHJ active layer but also minimizes the energy loss within the charge transport processes. In addition, the organic-inorganic LiSPS ionomer well circumvents the coherence issue of the organic BHJ photoactive layer on the ZnO EEL. Consequently, the enhanced charge transport and the lowered internal resistance between the BHJ photoactive layer and the ZnO/LiSPS EEL give rise to a dramatically reduced dark saturation current density and significantly minimized charge carrier recombination. As a result, the inverted BHJ PSCs with the ZnO/LiSPS EEL exhibit an approximatively 25% increase in power conversion efficiency. These results indicate our strategy provides an easy, but effective, approach to reach high performance inverted PSCs.