Silicon Heterojunction Solar Cells Combining an a-Si:H (n) Electron-collector with a PEDOT:PSS Hole-collector

We combine PEDOT:PSS as hole-selective layer on c-Si with a well-passivating electron-selective a-Si:H(n) layer in an alternative type of silicon heterojunction solar cell. As the interface between the PEDOT:PSS and the c-Si substrate plays a crucial role in the cell performance, we examine the impact of an interfacial SiOx tunneling layer between the c-Si substrate and the PEDOT:PSS in detail. We find that a natural SiOx layer grown within a couple of minutes leads to low J0 values ranging between (80 - 130) fA/cm2, allowing for Voc values of ∼690 mV. Implementation of this PEDOT:PSS/SiOx/c-Si junctions into solar cells with phosphorus-diffused n+ front results in low series resistance values of only 0.6 Ωcm2 and good fill factors >80% leading to efficiencies >20%. We then implement the PEDOT:PSS/SiOx/c-Si junction to the back of heterojunction cells with an a-Si:H(n)/ITO front, in order to demonstrate the feasibility of this novel cell concept, which has a higher Voc potential compared to cells with a conventionally processed front side. The cell efficiencies of the first batch reach 15.2%. This relatively moderate efficiency of the first cell batch is due to technological issues with the screen-printed front metallization grid, leading to poor fill factors of only 71%, whereas the Voc values of this first batch were already above 650 mV.State of Lower SaxonyGerman Federal Ministry of Economics and Energy/0325884

Organic-silicon Solar Cells Exceeding 20% Efficiency

Aftera briefreview of therecent evolvement oforganic-silicon heterojunction solar cells,we present here our latest measurements of the saturation current densities (J0) and contact resistances (RC) of crystalline silicon (c-Si)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) junctions. We determine the J0values by means of contactless carrier lifetime measurements and theRCvalues by comparing sheet resistance measurements with numerical device simulations of the corresponding test structure. Application of an adopted PEDOT:PSS blend and an optimized silicon surface treatmentresults in a minimalJ0value of46 fA/cm2, limiting the solar cell open-circuit voltage to Voc-limit=708 mV, and a minimal RCvalue of 100 m?cm2. Our optimized silicon surface pre-treatment in combination with the adapted PEDOT:PSS blendare successfully implemented into a cell process with the PEDOT:PSS layer located at the rear surface (the so-called 'BackPEDOT concept'). Record-high efficiencies of 18.3% and of 20.6% are achieved onn-type silicon and onp-type silicon wafers, respectively. Finally, we compare the internal quantum efficiency of our champion BackPEDOT solar cell with that of a state-of-the-art Al2O3/SiNx-passivated PERC solar cell

Improved surface passivation and reduced parasitic absorption in PEDOT:PSS/c-Si heterojunction solar cells through the admixture of sorbitol

We examine the impact of sorbitol admixture to the hole-conduction polymer PEDOT:PSS [poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)] on the characteristics of PEDOT:PSS/crystalline silicon heterojunction solar cells. We fabricate solar cells where the PEDOT:PSS layer is deposited as a hole-collecting contact at the cell rear, whereas the electron-collecting front is conventionally processed by means of phosphorus diffusion. Surprisingly, we observe that the admixture of the infrared-transparent sorbitol not only improves the short-circuit density of the solar cells due to the reduction of the infrared parasitic absorption, but also improves the passivation quality of PEDOT:PSS on silicon and hence the open-circuit voltage of the solar cells. The series resistance is not influenced by the admixture of sorbitol up to 4.0 wt.% sorbitol admixture in the PEDOT:PSS dispersion, but shows a pronounced increase for larger sorbitol contents. The optimal sorbitol content concerning efficiency is hence 4.0 wt.%, leading to an energy conversion efficiency of 20.4% at one sun, which is more than 1% absolute higher compared to the efficiency of the reference cells without sorbitol

Peculiarities of the emotional state of higher education students depending on the type of learning classes

Розглянуто особливості емоційного стану студентів залежно від виду навчального заняття. Досліджено міру самопочуття студентів та міру активності на лекційних заняттях порівняно з семінарськими і лабораторними; самопочуття та активності на семінарських заняттях порівняно з лабораторними; міру настрою студентів на лекційних заняттях порівняно з семінарськими і лабораторними заняттями,настрою на семінарських заняттях порівняно з лабораторними. З’ясовано, що у студентів самопочуття на лекціях має позитивні ознаки. Порівняно з лекціями, на лабораторних заняттях студенти мають більш позитивно виражене самопочуття. У студентів міравираженості активності більш висока на семінарах, ніж на лекціях. Порівняно з лекціями, на лабораторних заняттях студенти дуже активні. Швидкість і темп протікання психічних функцій студентів під час лабораторних заняттях мають більш високу міру вираженості, ніж під час семінарів. У студентів міра вираженості настрою більш висока на лекціях, ніж на семінарах. У якості перспективного напряму дослідження виділеноаналіз емоційних станів студентів залежно від гендерних особливостей і курсу навчання.Тhe features of emotional state of the students depending on a kind of learning classes are considered. The degree of well-being of students at lectures compared to seminars and laboratory classes, well-being at seminars compared to laboratory classes, the degree of activity of students at lectures compared to seminars and laboratory classes, activity at seminars compared to laboratory classes, the degree of mood of students at lectures compared to seminars and laboratory classes, the mood at seminars compared to laboratory classes have been studied.It has been found that the students have positive feelings at lectures. Compared to lectures, at laboratory classesthe students have positive well-being. The students have a higher degree of activity at seminars than at lectures. Compared to lectures, the students are very active at laboratory classes. The speed and pace of mental functions of the students during laboratory classes are expressed more intensive than during seminars. The students have a higher degree of mood expression at lectures than at seminars. As a promising area of research, the analysis of students' emotional states depending on gender characteristics and the course of study is highlighte

Parity forbidden excitations of Sr2CuO2Cl2 revealed by optical third-harmonic spectroscopy

We present the first study of nonlinear optical third harmonic generation in the strongly correlated charge-transfer insulator Sr2CuO2Cl2. For fundamental excitation in the near-infrared, the THG spectrum reveals a strongly resonant response for photon energies near 0.7 eV. Polarization analysis reveals this novel resonance to be only partially accounted for by three-photon excitation to the optical charge-transfer exciton, and indicates that an even-parity excitation at 2 eV, with a_1g symmetry, participates in the third harmonic susceptibility.Comment: Requires RevTeX v4.0beta

Стратегия развития компании на рынке медицинских услуг (на примере ООО «Медицинский Центр «Эверест»)

Объектом исследования в рамках выпускной квалификационной работы является разработка стратегии развития компании и рекомендаций по внедрению организационных инноваций с учетом потребностей клиентов. Предметом – план разработки стратегии развития данного предприятия. Цель работы: Разработка стратегии развития предприятия с учетом потребностей клиентов. Актуальность работы заключается в том, что грамотная стратегия развития медицинского предприятия является одной из важнейших областей ведения бизнеса в медицинской сфере. Развитие медицинского обслуживания поможет избавить людей от проблемы многочисленных затрат на лечение в зарубежных клиниках.The subject of the study as part of the final qualification work is the development of company development strategies and recommendations for implementing organizational innovations tailored to the needs of clients. The subject is the plan for developing strategies for the development of this enterprise. The purpose of the work: Developing strategies for the development of enterprises taking into account the needs of clients. The actuality of the work lies in the fact that a competent strategy for the development of a medical enterprise is one of the most important areas of business in the medical field. The development of medical services helps to save people from problems

Ultrafast terahertz probes of transient conducting and insulating phases in an electron–hole gas

Many-body systems in nature exhibit complexity and self-organization arising from seemingly simple laws. The long-range Coulomb interaction between electrical charges generates a plethora of bound states in matter, ranging from the hydrogen atom to complex biochemical structures. Semiconductors form an ideal laboratory for studying many-body interactions of quasi-particles among themselves and with lattice vibrations and light. Oppositely charged electron and hole quasi-particles can coexist in an ionized but correlated plasma, or form bound hydrogen-like pairs called excitons which strongly affect physical properties. The pathways between such states however remain elusive in near-visible optical experiments that detect a subset of excitons with vanishing center-of-mass momenta. In contrast, transitions between internal exciton levels which occur in the far-infrared at terahertz (10 s) frequencies are in dependent of this restriction suggesting their use as a novel pro be of pair dynamics. Here, we employ an ultrafast terahertz probe to directly investigate the dynamical interplay of optically-generated excitons and unbound electron-hole pairs in GaAs quantum wells. Our observations witness an unexpected quasi-instantaneous excitonic enhancement, reveal formation of insulating excitons on a hundred picosecond timescale and manifest conditions under which excitonic populations prevail