Search

The calculated levelized cost of electricity for single junction and tandem devices show that when the time for perovskite devices to degrade to 85% of the original output (T85) is only 3 years, tandem device are economically favorable.

Perovskite solar cell device performance is affected by optical and electronic losses. To minimize these losses in solar cells, it is important to identify their sources. Here, we report the optical and electronic losses arising from physically mixed interfacial layers between the adjacent component materials in highly efficient two terminal (2T) all-perovskite tandem, single-junction wide-bandgap, and single-junction narrow-bandgap perovskite-based solar cells. Physically mixed interfacial layers as the sources of optical and electronic losses are identified from spectroscopic ellipsometry measurements and data analysis followed by comparisons of simulated and measured external quantum efficiency spectra. Parasitic absorbance in the physically mixed regions between silver metal electrical contacts and electron transport layers (ETLs) near the back contact and a physical mixture of commercial indium tin oxide and hole transport layers (HTL) near the front electrical contact lead to substantial optical loss. A lower-density void + perovskite nucleation layer formed during perovskite deposition at the interface between the perovskite absorber layer and the HTL causes electronic losses because of incomplete collection of photogenerated carriers likely originating from poor coverage and passivation of the initially nucleating grains.

Introduction: Triple negative breast cancer (TNBC) is biologically defined by the absence of expression of ER, PR, and Her-2neu receptors and clinically has a poor prognosis. Racial disparities in breast cancer are well recognized with African-Americans and Hispanics having a higher prevalence of TNBC as compared to Caucasians. Advances in characterization of the molecular drivers of cancer hold the promise of better targeting TNBC and addressing some of the disparities in outcomes noted amongst minorities. However, based on the data from the cancer genome atlas (TCGA), the mutational landscape of TNBC in African-Americans was found to be similar to that of Caucasians. There is a remarkable lack of data regarding the genomic aberrations (GA) in TNBC in Hispanics. Of the more than 1000 breast cancer cases in the TCGA, only 37 are identified as Hispanic. Of these 37, only 4 had TNBC. Objective: Aim of the current study is to describe the GA seen in triple negative breast cancer patients, diagnosed at the Garbar Breast Cancer Center (GBCC) at TTUHSC-EP which serves a predominantly Mexican-American Hispanic population. Methods: Medical records of patients diagnosed with triple negative breast cancer at GBCC were reviewed. Of these, ones who had undergone next generation sequencing of the tumor were selected for review. Clinical, pathological and demographic data was extracted. Results were compared with the GA reported in the TCGA basal like subtype and the METABRIC (molecular taxonomy of breast cancer international consortium) triple negative cohorts. Results: Next generation sequencing data of representative tumor specimen for the detection of substitutions, insertion and deletion alterations (indels), and copy number alterations (CNAs) in 324 genes and select gene rearrangements, as well as genomic signatures including microsatellite instability (MSI) and tumor mutational burden (TMB) using DNA isolated from formalin-fixed paraffin embedded (FFPE) tumor tissue specimens was available for 17 patients. All were Hispanic females of Mexican-American heritage. Median age is 54 years (range 23-88). 14 (82.3%) had stage IV and 3 (17.7%) had stage III cancer. Of the 11 patients who underwent germ-line testing for inherited cancer predisposition syndrome, only one was found to have a pathogenic BRCA mutation. Tumor mutational burden(TMB) could not be determined in 3 cases. The average TMB in the remaining 14 cases was 4.7 mutations/Mb (Range: 1-10). All tumors were micro satellite stable. The top 5 gene mutations seen and their corresponding frequency in TCGA and METABRIC database are shown in the following tables. Conclusions: In a predominantly Hispanic cohort of advanced TNBC, we found a 100% prevalence of TP53 mutations and an increased frequency of NF1 and PTEN mutations as compared to reported frequencies in TCGA and METABRIC database. All cases were micro satellite stable and had low TMB. This suggests that molecular drives of cancer may be different in Hispanics and a better understanding of these may help address some of the disparities seen in outcomes in this group of patients. Frequency of 5 most commonly mutated genes seen at GBCC versus TCGAGeneGBCC (n=17)(%)TCGA(n-93)(%)pTP5310082.80.06NF117.62.150.004PIK3CA17.67.50.18PTEN17.61.080.0008RB111.74.30.21 Frequency of 5 most commonly mutated genes at GBCC vs METABRIC databaseGeneGBCC (n-17)(%)METABRIC (n-245)(%)pTP53100800.04NF117.63.270.004PIK3CA17.618.370.9PTEN17.66.50.08RB111.74.90.22 Citation Format: Sumit Gaur, Alexander Philipovskiy, Meghan McAlice, Onyedika V Umeanaeto, Kiran Ghimire. Tumor mutational profile of triple-negative breast cancer amongst hispanics of Mexican descent [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-11-05.

Food security is a major concern of the world in the context of increasing population, changing climate and declining scarce natural resources. Reducing food loss is equally important as increasing food production and productivity to feed the world, where 9.7 billion inhabitants were expected by 2050. Food loss can occur at several points along the food chain, however, harvest loss at the farm level is often overlooked which is directly impacting on sustainability. The paper attempts to estimate harvest loss at the farm level. A household survey was executed in 300 households from ten sample districts across Nepal. The percentage of harvest loss at the farm level was calculated for each crop grown as per - the season, per plot and priority. Likewise, the multiple regression was executed to determine the level of influence of the socio-economic factors on the post-harvest loss at the farm level for the major crops. The mean harvest loss at the farm level found around 5 percent for the reported crops. The multiple regression model demonstrated that at the farm level, socio-economic factors might have a smaller influence on harvest loss as compared to physical and biological contributing factors. Nevertheless, reducing the post-harvest loss will increase food availability and thus the food security.

Available with full text.

The annual energy yields for metal halide perovskite/copper indium gallium diselenide (CIGS) tandem photovoltaics have been calculated for 16 different bandgap combinations, using both 2 terminal and 4 terminal device designs, with fixed-tilt mounting as well as 1- and 2-axis tracking. Measured complex index of refraction data were used for the materials comprising the devices, and hourly irradiance data were extracted from Version 3 of the National Solar Radiation Database. Simulations were performed for Toledo OH, Golden CO, Phoenix AZ, and New Orleans LA, and the effect of local temperature variation was also considered. The combination of irradiance and temperature variations throughout the year cause different devices to be optimal at different times of the year. Interestingly, devices constructed to maximize AM1.5 photoconversion efficiency do not necessarily maximize the annual energy yield. A detailed analysis of the monthly energy yields at the different locations reveals the interplay between the changing light and temperature conditions. Over the course of the year these effects average to some degree so that annual energy yields that are close to the maximum possible value can be achieved by several different tandem device designs. The conclusions are valid for devices made with relatively thin perovskite layers, such as those used in champion efficiency devices. When the perovskite layers are thicker, however, the device is less tolerant to variation. Our results show that close matching of bandgap pairs is not essential for the fabrication of high-performance tandems. These findings should allow manufacturing efforts to proceed without the need for precise compositional control during formation of the absorber layers.

This paper has attempted to analyze the trend of pesticide import, formulation and consumption in Nepal. Nepal has diverse agro-ecological conditions and different agro-climatic conditions necessitate varieties of approaches to crop cultivation and crop protection. The average national use of pesticides in Nepal is 396g a.i./ha with the highest use in the vegetable. This review used relevant secondary data, and information. The study found that the fungicides are the major form of pesticides used in Nepal for the pest control and the trend of pesticides consumption is increasing for agricultural purposes. The Nepal Government has signed different international treaties, made rules and regulations and initiated different types of programs to minimize the use of pesticides.

Optical characterization and simulations have been applied to study formamidinium + cesium lead triiodide (FA1-xCsxPbI3) perovskite based thin films and solar cells. Near infrared to ultraviolet complex dielectric function (e = e1 + ie2) spectra of varying cesium-to-formamidinium ratios in solution processed perovskite thin films have been extracted. Analysis of these e spectra track changes in the positions of critical point (CP) energies, including band gaps and above band gap transitions, with increasing cesium contents. Band gap values are identified as the lowest energy CP, with additional sub-gap features attributed to the presence of defects. Absorption onset values, for which absorption coefficient (α) = 4000 cm−1, are extracted, with x = 0.2 showing the sharpest absorption edge and the least contribution to absorption from defects below the band gap. External quantum efficiency (EQE) simulations of solar cells using e spectra as input are compared to experimental results and corroborate that the observed sub-gap absorption is due to defects as it does not contribute to EQE.

Electrical transport properties [carrier concentration ( N ), mobility ( μ ), effective mass ( m *), resistivity ( ρ ), and scattering time ( τ )] are deduced from free carrier optical absorption using noncontacting optical Hall effect measurements. Here, we use this technique to determine N , μ , and m * for semiconductor absorber materials for photovoltaic (PV) devices. As case studies, PV component materials including thin-film methylammonium lead iodide, cadmium telluride, and copper indium diselenide as well as silicon wafers are characterized. Optical Hall effect measurements involve collecting long wavelength ellipsometric spectra under the application of an external magnetic field to determine N and μ for these thin films, and N , μ, and m * for the silicon wafers. ρ and τ are also determined for each sample from N , μ , and m * using the Drude model. In all cases, an additional transport parameter measurement is accessible relative to standard optical measurements alone even for the PV absorber materials having low free carrier absorption. As the technique is noncontacting, it could be very useful for the determination of transport properties of layers in complex multilayer stacks such as those in thin film and wafer-based PV devices.

An aluminum doped zinc oxide (ZnO:Al) thin film is prepared on soda lime glass by radio frequency (RF) magnetron sputtering. Optical properties of ZnO:Al in the form of complex dielectric function ( e = e 1 + i e 2 ) spectra are studied from 0.4 to 6 meV and 0.035 to 5.89 eV using spectroscopic ellipsometry. The film is found to have an optical band gap of 3.62 ± 0.01 eV and an extrapolated DC dielectric constant of 9.072. Resistivity, scattering time, mobility, and carrier concentration are found to be (2.250 ± 0.007) × 10 −3 Ω-cm, 5.1 ± 0.7 fs, 20.8 cm 2 V −1 s −1 , and 1.3 × 10 20 cm −3 respectively. Resistivity and scattering time resulting from fitting to measurements are found to depend on the spectral range modeled, such that the inclusion of increasingly longer wavelengths results in a convergence to direct electrical property measurements.

Monolithic two-terminal (2-T) all-perovskite tandem solar cells are a promising candidate for the next generation solar cells with ultrahigh efficiency and low fabrication cost. Here, we report on the fabrication of 2-T all-perovskite tandem solar cells consisting of solution-processed wide-bandgap and low-bandgap perovskite subcells connected by a vacuum processed interconnection layer. We employed a bulk-passivation strategy to enlarge the grain size, increase carrier mobilities, reduce electronic disorder, and suppress trap-assisted recombination in the low bandgap mixed Sn-Pb perovskite films, which leads to improved performance of low bandgap perovskite solar cells with an absorber thickness over 750 nm. This advance in high-quality low-bandgap perovskite layers enables the fabrication of efficient 2-T all-perovskite solar cells with power conversion efficiencies of more than 21% and decent stability. Our approach provides a suitable pathway to realize ultra-high efficiency 2-T all-perovskite tandem solar cells.

The paper attempts to explore the relationship between federalism and rural development. Federalism is a division of power, responsibility and accountability to bring the administrative and political power closer to the ground and essentially to increase the good governance. On the other hand, rural development is a complex and multidimensional issue- especially much demanding for least developed and developing countries. A descriptive and qualitative approach was carried out to study the complex relationship between rural development and federalism. Similarly, a SWOT analysis was carried out to have a better understanding of the relationship. The study found that there is significant potentiality for accelerated development of rural landscape in federalism if carefully executed. However, on the other hand, federalism may pose several risks on rural development and may restrict the development pace if not executed with appropriate care and understanding. Therefore, the study concludes that cooperation and coordination among the federal structures are crucial for better development of the rural economy.

The anisotropic optical properties of single crystal SrLaAlO4 are investigated using spectroscopic ellipsometry over the range from 0.74 to 5.90 eV. Divided spectral range analysis of ellipsometric and Mueller matrix spectra are used to obtain the sample structural parameters (surface roughness thickness and void fraction). The ordinary and extra-ordinary optical properties in the form of complex dielectric function, ϵ = ϵ1 + iϵ2 (or complex index of refraction, N = n + ik), spectra are extracted from the same analysis. The observed birefringence is ∼ 0.025 in the transparent range. An upper limit for the indirect gap at 3.01 ± 0.01 eV and a critical point at 5.54 ± 0.01 eV are identified within the measured spectral range.

Introduction: Hispanics represent the largest minority group in the United States (U.S.), with 57.5 million individuals. The majority of Hispanics in the U.S. reside in the Southwest region, and >11 million live in the state of Texas. Health disparities for Hispanic cancer patients have previously been linked to disproportionate poverty and other barriers to optimal healthcare. In the case of acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL), Hispanics were found to be diagnosed at a younger age and have worse overall survival (OS) compared with non-Hispanic whites (NHWs) (ACS Cancer Facts & Figures for Hispanics/Latinos 2018-2020). However, little is known about incidence and survival for Hispanic blood cancer patients residing at the U.S./Mexico border. Methods: We retrospectively reviewed data from the Texas Cancer Registry for hematologic malignancies diagnosed in the state of Texas between 1995 and 2016, focusing our analysis on chronic and acute leukemia's (both myeloid and lymphoid), myelodysplastic syndrome (MDS), and myeloproliferative neoplasms (MPNs). Survival for Hispanic and NHW groups was compared using the log-rank test, and Cox regression analyses adjusting for age and diagnosis. Differences in age at diagnosis were evaluated using t-tests and generalized linear models. Research was conducted according to a local IRB-approved protocol in accordance with the Declaration of Helsinki. Results: Of the 69,941 cases of hematologic malignancies with available information throughout the state of Texas, 18.29% identified as Hispanic. We found that Hispanic patients were diagnosed at a significantly younger age in all diseases analyzed (p Conclusions: Hispanics are diagnosed at a significantly younger age than NHWs in all blood malignancies analyzed. Hispanic patients with AML, MDS, and CML had significantly better OS compared to NHWs in unadjusted analyses, which could be explained by the reduced age of diagnosis. Hispanics with ALL, AML, or CML diagnosed near the U.S./Mexico border demonstrate worse OS compared with Hispanics diagnosed in other areas of Texas. In age-adjusted analyses, Hispanic patients with ALL or APL have a worse OS compared with NHWs. There appears to be evidence that disparities in outcome by ethnicity may be different in El Paso compared with the rest of Texas. Future Directions: Our data demonstrates blood cancer disparities present in our region. Further study is required to identify factors responsible for the disparity in OS, and to identify ways to address it. Citation Format: Alfonso E. Bencomo, Andres J. Rubio, Mayra A. Gonzalez, Idaly M. Olivas, Joshua J. Lara, Kiran Ghimire, Osvaldo Padilla, Angelica Padilla, Nawar Hakim, Attilio Orazi, Javier Corral, Alexander Philipovskiy, Sumit Gaur, Anna M. Eiring. Retrospective study of incidence and survival for patients with hematological malignancies residing at the U.S./Mexico border [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4343.

The majority of the population in developing countries resides in the rural area. Development itself cannot address the challenges of the rural area since its economic, political and environmental landscape is different from an urban area. The paper attempts to assess the rural dimension aspect of Nepali Agriculture Policy since rural development and agricultural development is closely resembled due to an agrarian-based economy of the country and a large rural population. Therefore, a critical review of National Agriculture Policy, 2004 (NAP-2004) was carried out under “Commercialization of Agriculture”, “Food Security”, “Rural Infrastructure”, “Gender”, “Climate Change” and “Social Inclusion” thematic area. The results showed that NAP-2004 satisfactorily address rural development albeit ample space for improvement. The findings of the paper could be beneficial to policymakers and development workers in the field of rural development and agriculture along with academicians having interest in it.

Quite high efficiencies exceeding 20% have been realized in solar cells incorporating organic-inorganic hybrid perovskites (APbX3), which have a unique structure with a center cation [A = CH3NH3+, HC(NH2) 2 + ] located within a PbX3− cage (X = I, Br, Cl). Superior characteristics of hybrid perovskite solar cells can be understood from the nature of optical transitions and the efficient carrier collection in the device. From these points of view, this chapter provides details on optical properties of various hybrid perovskite materials and carrier dynamics in the solar cells. In particular, based on the first-principles analyses of different perovskite materials, we present universal rules that allow the unified interpretation of the optical absorption phenomenon in APbX3 perovskites. The external quantum efficiency (EQE) analysis further reveals that high short-circuit current densities (>20 mA/cm2) observed in the perovskite solar cells originate from electric-field-assisted carrier collection and the suppressed optical losses in the devices. Although hybrid perovskites have quite favorable characteristics for solar cells, these materials exhibit rather intense phase change upon exposure to humid air. In this chapter, the degradation process of CH3NH3PbI3 in humid air, characterized by applying ellipsometry technique, is further presented and discussed., N. J. Podraza and K. Ghimire would like to acknowledge D. Zhao, A. Cimaroli, Y. Ke, F. Hong, T. Shi, and Prof. Y. Yan for providing samples and materials; M. Junda for graphical assistance; and the National Science Foundation for financial support (CHE-1230246). M. I. Alonso acknowledges financial support from the Spanish Ministry of Economy and Competitiveness, through grants CSD2010-00044, MAT2015-70850-P, and the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV-2015-0496).

Optical characterization and simulations have been applied to study formamidinium + cesium lead triiodide (FA}1}$X \mathbf{Cs} X$textbf{PbI3}\textbf{) perovskite thin films and solar cells. Near infrared to ultraviolet complex index of refraction ($N = n +_{\mathbf{\, }} ik$) spectra of varying cesium-to-formamidinium ratios in solution processed perovskite thin films have been extracted. Critical point transitions and the absorption onset are extracted, with $x =$ 0.2 showing the sharpest absorption edge and least contribution from defects to absorption near the band edge. External quantum efficiency simulations of perovskite based solar cells using optical properties as input are performed and compared to experimental device results.

Agriculture, which generates two-third of the employment and one-third of the GDP in Nepal, is an important sector since Nepal is a small, landlocked country with low income. The government enacted the National Agriculture Policy in 2004 (NAP-2004) as an umbrella policy in the agricultural sector to guide all sectoral policies coming in the future. The paper has examined NAP-2004 by using the Strength, Weakness, Opportunity and Threat (SWOT) analysis technique. For the analysis, secondary data, the publications of the government and the international organizations as well as peer-reviewed articles were reviewed. The strength and weakness were analyzed by using nine different indicators. The results of the paper will be instrumental for improvement of the agricultural policy.

Optical properties of commercially available gadolinium gallium garnet (Gd3Ga5O12) single crystals have been studied over a spectral range from 0.034 to 5.887 eV using spectroscopic ellipsometry and transmittance measurements via a near infrared to ultraviolet spectral range multichannel ellipsometer and a Fourier transform infrared (FTIR) ellipsometer. The complex dielectric function (ϵ = ϵ1 + iϵ2) spectra from 0.034 to 5.887 eV have been determined. Transmission measurements have been performed to more accurately extract the absorption coefficient near the band edge and identify sub band gap features. Analysis of ϵ for Gd3Ga5O12 indicates a direct band gap at 5.66 ± 0.01 eV, sub band gap absorption features from 3.95 to 5.06 eV, and nine transverse optical phonon modes at 288, 313, 329, 361, 370, 467, 577, 609, and 670 cm−1 and longitudinal optical phonon modes at 288, 327, 338, 370, 461, 490, 592, 663, and 707 cm−1.

Currently, the pesticides are the global core concern because it is a boon to farmers against increasing disease-pest and simultaneously, pesticide residue is the major anxiety regarding human health. For that reason, identification and determination of factors affecting the application of pesticides are essential. To identify and evaluate determinants of pesticides application in Nepal, a household survey of 300 households was carried-out and an empirical analysis was done using multivariate probit model. Moreover, powder and liquid forms of pesticides were considered for summer and winter season in vegetable farming, which was assigned as outcome variables. Likewise, socio-economic, demographic, farm-level and perception data were considered as explanatory variables. Use of chemical fertilizers, age and gender of head of household, household size and access to weather information were found the most influencing factors. Moreover, forms of pesticides and growing seasons were found complementary to each other. Therefore, devising the policy options accordingly should balance needs of farmers and health of consumers.

Optical properties of highly chromium doped (2–4 at.%) zinc sulfide made by pulsed laser deposition have been studied by spectroscopic ellipsometry in the spectral range of 0.73–5.90 eV. The characteristic optical features of the ZnS are a direct bandgap with absorption onset at 3.6 eV, with E0, E1 and E2 critical points around 3.7, 5.7 and 7 eV. Excitonic effects were observed to be strong in this material – in line with the literature. The sub-bandgap absorption accredited to the chromium doping appears as a broad sub-bandgap feature increasing monotonously with increased doping concentration at a given growth temperature. In this report, we discuss three different approaches to extract and analyze the optical properties in terms of the complex dielectric function.

We demonstrate a solar cell based on a thin layer of metal directly deposited on an n-doped semiconductor structure, forming a Schottky barrier acting as a semi-selective contact for an electron temperature driven cell. Absorption of light is shown to be by free carrier absorption in the metal layer for illumination with wavelengths of light below the semiconductor band gap, giving rise to an IV characteristic with a reverse bias slope dependent on electron temperature. Illumination with light in excess of the band gap reveals a standard Schottky cell IV characteristic.

Introduction: Hispanics represent the largest minority group in the United States (U.S.), with 57.5 million individuals (18% of the population). Most U.S. Hispanics are of Mexican origin (63.2%), followed by Puerto Rican (9.5%), Cuban (3.9%), Salvadoran (3.8%), and Dominican (3.3%), but distribution varies by state. The majority of Hispanics in the U.S. reside in the Southwest region, and >11 million live in the state of Texas. Cancer is the leading cause of death in the Hispanic population, accounting for 21% of deaths in people of all ages. Health disparities for Hispanic cancer patients have previously been linked to disproportionate poverty and other barriers to optimal healthcare, and in the case of acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL), Hispanics were found to be diagnosed younger and to have worse overall survival (OS) than Non-Hispanic whites (NHWs) (ACS. Cancer Facts & Figures for Hispanics/Latinos 2018-2020). However, little is known about incidence and survival for Hispanic blood cancer patients residing at the U.S./Mexico border. To understand the impact of Hispanic ethnicity on outcomes for blood cancer patients diagnosed in this area, we examined OS in adult patients with hematologic malignancies throughout the state of Texas compared to Texas Health Service Region (HSR) 10, encompassing El Paso County. Methods: We retrospectively reviewed data available from the Texas Cancer Registry for hematologic malignancies diagnosed in the state of Texas between 1995 and 2016, focusing our analysis on chronic and acute leukemias (both myeloid and lymphoid), myelodysplastic syndrome (MDS), and myeloproliferative neoplasms (MPNs). Survival for Hispanic and NHW groups was compared using the log-rank test, and Cox regression analyses adjusting for age and diagnosis. Differences in age at diagnosis were evaluated using t-tests and generalized linear models. Similar analyses compared Hispanic patients from HSR 10 versus Hispanic patients from the rest of Texas. Research was conducted according to a local Institutional Review Board-approved protocol in accordance with the Declaration of Helsinki. Results: Of the 69,941 cases of hematologic malignancies with available information throughout the state of Texas, 18.29% self-identified as Hispanic. Surprisingly, in unadjusted analyses, Hispanic patients had significantly better OS than NHWs diagnosed with AML (p Conclusions: While Hispanic patients with AML, MDS, and CML had significantly better OS compared to NHWs in Texas as a whole, this could be explained by a significant reduction in the age of diagnosis for Hispanics. However, when comparing across Texas, El Paso Hispanics with ALL, AML, and CML have a worse prognosis than in the rest of the state. There appears to be evidence that disparities in outcome by ethnicity may be different in El Paso compared with the rest of Texas. Further study is required to identify factors responsible for the disparity in OS. Disclosures No relevant conflicts of interest to declare.

Mixed tin (Sn)-lead (Pb) perovskites with high Sn content exhibit low bandgaps suitable for fabricating the bottom cell of perovskite-based tandem solar cells. In this work, we report on the fabrication of efficient mixed Sn-Pb perovskite solar cells using precursors combining formamidinium tin iodide (FASnI3) and methylammonium lead iodide (MAPbI3). The best-performing cell fabricated using a (FASnI3)0.6(MAPbI3)0.4 absorber with an absorption edge of ∼1.2 eV achieved a power conversion efficiency (PCE) of 15.08 (15.00)% with an open-circuit voltage of 0.795 (0.799) V, a short-circuit current density of 26.86(26.82) mA/cm(2), and a fill factor of 70.6(70.0)% when measured under forward (reverse) voltage scan. The average PCE of 50 cells we have fabricated is 14.39 ± 0.33%, indicating good reproducibility.

CH 3 NH 3 PbI 3 perovskite films for photovoltaics (PV) have been deposited by vapor deposition and solution processing. Spectroscopic ellipsometry from the near infrared to ultraviolet (0.75 to 5.89 eV) is used to study the optical response of CH 3 NH 3 PbI 3 . In-situ spectroscopic ellipsometry is applied to monitor CH3NH3PM3 undergoing degradation in laboratory ambient conditions to study the degradation / decomposition of CH 3 NH 3 PbI 3 and evolution of unreacted and phase segregated materials (PbI 2 , CH 3 NH 3 I) found at surface / ambient and substrate / film interfaces.

CH3NH3PbX3 (X=I, Cl) perovskite films of interest for photovoltaics (PV) devices have been deposited by (i) evaporation followed by vapor annealing and (ii) co-evaporation. Near infrared to ultraviolet spectroscopic ellipsometry has been used to determine the spectroscopic optical response for vapor-annealed material ex situ and co-evaporated material in situ during growth. Real time spectroscopic ellipsometry (RTSE) applied during co-evaporation has tracked the formation and time evolution of perovskite and phase segregated layers at the substrate and surface interfaces. Good agreement between density functional theory (DFT) calculations of optical response and experimental measurements has also been demonstrated.

Through detailed device characterization using cross-sectional Kelvin probe force microscopy (KPFM) and trap density of states measurements, we identify that the J–V hysteresis seen in planar organic–inorganic hybrid perovskite solar cells (PVSCs) using SnO2 electron selective layers (ESLs) synthesized by low-temperature plasma-enhanced atomic-layer deposition (PEALD) method is mainly caused by the imbalanced charge transportation between the ESL/perovskite and the hole selective layer/perovskite interfaces. We find that this charge transportation imbalance is originated from the poor electrical conductivity of the low-temperature PEALD SnO2 ESL. We further discover that a facile low-temperature thermal annealing of SnO2 ESLs can effectively improve the electrical mobility of low-temperature PEALD SnO2 ESLs and consequently significantly reduce or even eliminate the J–V hysteresis. With the reduction of J–V hysteresis and optimization of deposition process, planar PVSCs with stabilized output powers up to 20.3% are achieved. The results of this study provide insights for further enhancing the efficiency of planar PVSCs.