Predicting Solar Cell Performance from Terahertz and Microwave Spectroscopy

Mobilities and lifetimes of photogenerated charge carriers are core properties of photovoltaic materials and can both be characterized by contactless terahertz or microwave measurements. Here, the expertise from fifteen laboratories is combined to quantitatively model the current voltage characteristics of a solar cell from such measurements. To this end, the impact of measurement conditions, alternate interpretations, and experimental inter laboratory variations are discussed using a Cs,FA,MA Pb I,Br 3 halide perovskite thin film as a case study. At 1 sun equivalent excitation, neither transport nor recombination is significantly affected by exciton formation or trapping. Terahertz, microwave, and photoluminescence transients for the neat material yield consistent effective lifetimes implying a resistance free JV curve with a potential power conversion efficiency of 24.6 . For grainsizes above amp; 8776;20 nm, intra grain charge transport is characterized by terahertz sum mobilities of amp; 8776;32 cm2 V amp; 8722;1 s amp; 8722;1. Drift diffusion simulations indicate that these intra grain mobilities can slightly reduce the fill factor of perovskite solar cells to 0.82, in accordance with the best realized devices in the literature. Beyond perovskites, this work can guide a highly predictive characterization of any emerging semiconductor for photovoltaic or photoelectrochemical energy conversion. A best practice for the interpretation of terahertz and microwave measurements on photovoltaic materials is presente

Financial statements frauds: does their intensity have a connection with earnings management?

This study investigates the relationship between earnings management and financial statements frauds. We examine how earnings management practices; done in the two years before the fraud, impact the likelihood of fraud occurrence. Moreover, we introduce a new measure for the fraud intensity. Using a sample of 70 fraud and 70 no-fraud firms, we find that firms committing fraud of higher intensity have managed earnings in the two years before the fraud occurrence. This paper contributes to the literature about fraud antecedents because it is the first study measuring the relationship between earnings management and the intensity of the fraud, and it can be also useful for practitioners, because using the analysis of earnings management practices, analysts can foresee and prevent financial statements frauds

Haptichem

Haptichem is a 2-year project where haptic interaction has been adopted within the chemistry education field. This report describes the main contributions of the project

Acute respiratory distress caused by a giant mediastinal lipoblastoma in a 16-month-old boy.

Lipoblastoma is a rare benign tumor arising from embryonic fat; it occurs mainly in the extremities and almost exclusively in infants and children younger than 3 years. We present a case of giant mediastinal lipoblastoma in a 16-month-old boy who presented with acute respiratory distress. The mass was completely excised through a left posterolateral thoracotomy. The postoperative course was uneventful, and the pathologic final diagnosis was lipoblastoma. Although extremely rare, mediastinal lipoblastoma can be life threatening; therefore, it should be included in the differential diagnosis of mediastinal mass in younger subject