Ion-modulated radical doping of spiro-OMeTAD for more efficient and stable perovskite solar cells.

Record power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) have been obtained with the organic hole transporter 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9'-spirobifluorene (spiro-OMeTAD). Conventional doping of spiro-OMeTAD with hygroscopic lithium salts and volatile 4-tert-butylpyridine is a time-consuming process and also leads to poor device stability. We developed a new doping strategy for spiro-OMeTAD that avoids post-oxidation by using stable organic radicals as the dopant and ionic salts as the doping modulator (referred to as ion-modulated radical doping). We achieved PCEs of >25% and much-improved device stability under harsh conditions. The radicals provide hole polarons that instantly increase the conductivity and work function (WF), and ionic salts further modulate the WF by affecting the energetics of the hole polarons. This organic semiconductor doping strategy, which decouples conductivity and WF tunability, could inspire further optimization in other optoelectronic devices.

Conformal quantum dot-SnO2 layers as electron transporters for efficient perovskite solar cells.

Improvements to perovskite solar cells (PSCs) have focused on increasing their power conversion efficiency (PCE) and operational stability and maintaining high performance upon scale-up to module sizes. We report that replacing the commonly used mesoporous-titanium dioxide electron transport layer (ETL) with a thin layer of polyacrylic acid-stabilized tin(IV) oxide quantum dots (paa-QD-SnO2) on the compact-titanium dioxide enhanced light capture and largely suppressed nonradiative recombination at the ETL-perovskite interface. The use of paa-QD-SnO2 as electron-selective contact enabled PSCs (0.08 square centimeters) with a PCE of 25.7% (certified 25.4%) and high operational stability and facilitated the scale-up of the PSCs to larger areas. PCEs of 23.3, 21.7, and 20.6% were achieved for PSCs with active areas of 1, 20, and 64 square centimeters, respectively.

A Retrospective and Prospective Follow-up Study of Psychological Distress in the Danwon High School Survivors of the Sewol Ferry Disaster.

OBJECTIVE: We monitored a group of students from Danwon High School who survived the Sewol ferry disaster for 27 months to examine the course of their psychological symptoms. METHODS: We performed a chart review at the Danwon High School Mental Health Center at the following time points (T): 9 months (T1), 12 months (T2), and 15 months (T3) after the disaster. Additionally, we performed a follow-up review at 27 months (T4). Subjects completed the 'State' section of the State-Trait Anxiety Inventory for Children, the Center for Epidemiological Studies-Depression assessment, the Child Report of Post-traumatic Symptoms, and the Inventory of Complicated Grief. Data from the 32 subjects who completed all four assessments were used in the statistical analyses. RESULTS: Scores of psychological variables tended to increase until T2 and then slowly decreased until T4. The severity of anxiety and complicated grief symptoms changed significantly over time, but the severity of depression and posttraumatic stress symptoms did not. CONCLUSION: We found that the symptoms of anxiety and complicated grief reported by Sewol ferry survivors from Danwon High School were exacerbated at the first anniversary of the disaster, but these symptoms subsided after the students graduated from high school.

Factors Associated with Complicated Grief in Students Who Survived the Sewol Ferry Disaster in South Korea.

OBJECTIVE: The Sewol ferry disaster caused shock and grief in South Korea. The aim of this study was to identify the factors associated with symptoms of complicated grief (CG) among the surviving students 20 months after that disaster. METHODS: This study was conducted using a cross-sectional design and a sample of 57 students who survived the Sewol ferry disaster. Data were collected using the following instruments: Inventory of Complicated Grief (ICG), the Lifetime Incidence of Traumatic Events-Child, the Child Report of Post-Traumatic Symptoms (CROPS), KIDSCREEN-27, Family Adaptability and Cohesion Evaluation Scales-III, the Peri-traumatic Dissociation-Post-traumatic Negative Beliefs-Post-traumatic Social Support scale, and the Strengths and Difficulties Questionnaire. A generalized linear model using a log link and Poisson distribution was performed to identify factors associated with symptoms of CG. RESULTS: The mean score on the ICG was 15.57 (standard deviation: 12.72). Being born in 1999, a higher score on the CROPS and a lower score in autonomy and relationship with parents on the KIDSCREEN-27 were related to higher levels of CG. CONCLUSION: Twenty months after the Sewol ferry disaster, 24.5% of surviving students were suffering from CG. This study uncovered a vulnerable population of bereaved children at high risk for CG.

Social Support as a Mediator of Posttraumatic Embitterment and Perceptions of Meaning in Life among Danwon Survivors of the Sewol Ferry Disaster.

PURPOSE: Our research was designed to test and explore the relationships among embitterment, social support, and perceptions of meaning in life in the Danwon High School survivors of the Sewol ferry disaster. MATERIALS AND METHODS: Seventy-five Sewol ferry disaster survivors were eligible for participation, and were invited to participate in the study 28 months after the disaster. Forty-eight (64%) survivors (24 males, 24 females) completed questionnaires; the Posttraumatic Embitterment Disorder (PTED) scale, the Functional Social Support Questionnaire (FSSQ), and the Meaning in Life Questionnaire (MLQ). RESULTS: PTED scores were negatively correlated with scores on the FSSQ and the Presence of Meaning (MLQ-P) (r=-0.43 and -0.40, respectively). The hierarchical regression analysis showed that FSSQ scores may fully mediate the effects of PTED scores on MLQ-P scores, given that the indirect effect was significant whereas the direct effect was not (95% confidence interval=-0.5912 to -0.0365). CONCLUSION: These findings imply that therapies targeting embitterment may play a vital role in increasing positive cognitions, such as those related to perceived social support and the meaningfulness of life.

Conjugated polyelectrolyte hole transport layer for inverted-type perovskite solar cells.

Organic-inorganic hybrid perovskite materials offer the potential for realization of low-cost and flexible next-generation solar cells fabricated by low-temperature solution processing. Although efficiencies of perovskite solar cells have dramatically improved up to 19% within the past 5 years, there is still considerable room for further improvement in device efficiency and stability through development of novel materials and device architectures. Here we demonstrate that inverted-type perovskite solar cells with pH-neutral and low-temperature solution-processable conjugated polyelectrolyte as the hole transport layer (instead of acidic PEDOT: PSS) exhibit a device efficiency of over 12% and improved device stability in air. As an alternative to PEDOT: PSS, this work is the first report on the use of an organic hole transport material that enables the formation of uniform perovskite films with complete surface coverage and the demonstration of efficient, stable perovskite/fullerene planar heterojunction solar cells.

An organic surface modifier to produce a high work function transparent electrode for high performance polymer solar cells.

Modification of an ITO electrode with small-molecule organic surface modifier, 4-chloro-benzoic acid (CBA), via a simple spin-coating method produces a high-work-function electrode with high transparency and a hydrophobic surface. As an alternative to PEDOT:PSS, CBA modification achieves efficiency enhancement up to 8.5%, which is attributed to enhanced light absorption within the active layer and smooth hole transport from the active layer to the anode.

Boosting the power conversion efficiency of perovskite solar cells using self-organized polymeric hole extraction layers with high work function.

A self-organized hole extraction layer (SOHEL) with high work function (WF) is designed for energy level alignment with the ionization potential level of CH3 NH3 PbI3 . The SOHEL increases the built-in potential, photocurrent, and power conversion efficiency (PCE) of CH3 NH3 PbI3 perovskite solar cells. Thus, interface engineering of the positive electrode of solution-processed planar heterojunction solar cells using a high-WF SOHEL is a very effective way to achieve high device efficiency (PCE = 11.7% on glass).

Mixed solvents for the optimization of morphology in solution-processed, inverted-type perovskite/fullerene hybrid solar cells.

We investigate mixed solvents of N,N-dimethylformamide (DMF) and γ-butyrolactone (GBL) to produce the smooth surface of a perovskite film and uniform crystal domains. This ideal morphology from mixed solvents enhances the power conversion efficiency to over 6% by improving the exciton dissociation efficiency and reducing the recombination loss at both interfaces of PEDOT:PSS/perovskite and perovskite/PCBM.

Vapor coating method using small-molecule organic surface modifiers to replace N-type metal oxide layers in inverted polymer solar cells.

We investigate a simple fabrication method for vapor coating small-molecule organic interlayers as replacements for metal oxide films. The interfacial layers, which serve both as both surface modifiers to reduce the substrate work function and electron selective layers, maximize light absorption within the active layer while improving electron transport and compatibility between the active layer and cathode, leading to a ∼22% enhancement in power conversion efficiency and similar air stability compared to devices using a ZnO layer.

Inverted colloidal quantum dot solar cells.

An inverted architecture of quantum dot solar cells is demonstrated by introducing a novel ZnO method on top of the PbS CQD film. Improvements in device characteristics stem from constructive optical interference from the ZnO layer that enhances absorption in the PbS CQD layer. Outstanding diode characteristics arising from a superior PbS/ZnO junction provide a further electronic advantage.

Effects of ionic liquid molecules in hybrid PbS quantum dot-organic solar cells.

We investigated the effect of ionic liquid molecules (ILMs) in hybrid quantum dot-organic solar cells (HyQD-OSCs). The insertion of an ILM layer between PbS and phenyl-C61-butyric acid methyl ester (PCBM) can shift the band edge of PCBM closer to the vacuum level of PbS due to spontaneous dipole polarization. Because of this new architecture, improvements in device performance were achieved, including increases in open-circuit voltage (VOC, from 0.41 V to 0.49 V), fill factor (FF, from 0.48 to 0.59), and power conversion efficiency (PCE, from 1.62% to 2.21%), compared to reference devices under AM 1.5G illumination at 100 mW cm(-2). We observed that treatment of the PbS layer with ILMs causes a significant increase in work function from 3.58 eV to 3.93 eV. Furthermore, the ILMs layer minimizes the contact resistance between PbS and PCBM due to the improved compatibility between the two layers, confirmed as a decrease in charge transfer resistance, as measured by electrical impedance spectroscopy.

Gold(I)-catalyzed intramolecular hydroamination of alkyne with trichloroacetimidates.

[reaction: see text] A study on the gold (I)-catalyzed intramolecular hydroamination of trichloroacetimidates derived from propargyl and homopropargyl alcohols is described. In the presence of 2-5 mol % of cationic Au(I) complex, a variety of trichloroacetimidates undergo efficient hydroamination under an exceptionally mild condition. An orthogonality of the current catalytic protocol with those using a stoichiometric electrophile as well as a preliminary synthetic application as a stable precursor of 2-acylamino-1,3-diene has been demonstrated.