Neste trabalho são apresentados os resultados obtidos no desenvolvimento de um sistema especificado para realizar testes na caracterização de dispositivos fotodetectores como fotodiodos de avalanche. O sistema de ensaios elaborado pretende auxiliar com na caracterização da fotodetecção em dispositivos de acoplamento de cargas com multiplicação de elétrons (EMCCD). O objetivo deste trabalho é avaliar o desempenho dos dispositivos fotodetectores para caracterizar os parâmetros mais significativos no processo da transdução óptica de modo a colaborar no projeto da eletrônica embarcada de controle e leitura da informação contida no EMCCD. A tecnologia da multiplicação dos elétrons em dispositivos CCD e diodos de avalanche têm aplicações importantes na vigilância de ambiente de luminosidade reduzida, astronomia, além de outras aplicações de imagens científicas incluindo as de baixo nível de bioluminescência para identificação de drogas e aplicações da engenharia genética. Para efeito de avaliação do desempenho do sistema fotodetector foi necessário desenvolver uma infra-estrutura para ter controle adequado da temperatura de operação do EMCCD. Foram nomeadas as opções com uma montagem de resfriamento com células Peltier e uma opção por criogenia resfriada com nitrogênio líquido. Os resultados obtidos são úteis na detecção de sinais luminosos ultrafracos minimizando o ruído do detector na aquisição de imagens com o auxilio da instrumentação de um filtro óptico sintonizável que será integrado no telescópio SOAR de 4 metros, instalado no Chile, para observações melhoradas com óptica adaptativa. / This work presents the results obtained in the development of a system specified to perform tests in the characterization of photo-detectors devices such as avalanche photodiodes. The test system is prepared to contribute to the characterization of the photo-detection in charge-coupled devices with electron multiplication (EMCCD). The objective of this study is to evaluate the performance of photo-detectors devices to characterize the most significant parameters in the optic transduction in order to collaborate in the project of an embedded electronic system for controlling and reading the information contained with the EMCCD. The technology of the electron multiplication in CCD devices and avalanche diodes has important applications in monitoring the environment of low light, astronomy and other scientific imaging applications including the low level of bioluminescence for the identification of drugs and applications of genetic engineering. For purposes of assessing the performance of the photo-detector it was necessary to develop an infrastructure to have proper control of the operating temperature of the EMCCD. Options were named with a montage of Peltier cell cooling and a choice of cryogenically cooled with liquid nitrogen. The results are useful in the detection of ultra weak light signals while minimizing detector noise during the acquisition of images from instrument comprising an optical tunable filter, that will be integrated into SOAR 4 meters telescope, installed in Chile, for observations improved with adaptive optics.

Neste trabalho são apresentados os resultados obtidos no desenvolvimento de um sistema especificado para realizar testes na caracterização de dispositivos fotodetectores como fotodiodos de avalanche. O sistema de ensaios elaborado pretende auxiliar com na caracterização da fotodetecção em dispositivos de acoplamento de cargas com multiplicação de elétrons (EMCCD). O objetivo deste trabalho é avaliar o desempenho dos dispositivos fotodetectores para caracterizar os parâmetros mais significativos no processo da transdução óptica de modo a colaborar no projeto da eletrônica embarcada de controle e leitura da informação contida no EMCCD. A tecnologia da multiplicação dos elétrons em dispositivos CCD e diodos de avalanche têm aplicações importantes na vigilância de ambiente de luminosidade reduzida, astronomia, além de outras aplicações de imagens científicas incluindo as de baixo nível de bioluminescência para identificação de drogas e aplicações da engenharia genética. Para efeito de avaliação do desempenho do sistema fotodetector foi necessário desenvolver uma infra-estrutura para ter controle adequado da temperatura de operação do EMCCD. Foram nomeadas as opções com uma montagem de resfriamento com células Peltier e uma opção por criogenia resfriada com nitrogênio líquido. Os resultados obtidos são úteis na detecção de sinais luminosos ultrafracos minimizando o ruído do detector na aquisição de imagens com o auxilio da instrumentação de um filtro óptico sintonizável que será integrado no telescópio SOAR de 4 metros, instalado no Chile, para observações melhoradas com óptica adaptativa. / This work presents the results obtained in the development of a system specified to perform tests in the characterization of photo-detectors devices such as avalanche photodiodes. The test system is prepared to contribute to the characterization of the photo-detection in charge-coupled devices with electron multiplication (EMCCD). The objective of this study is to evaluate the performance of photo-detectors devices to characterize the most significant parameters in the optic transduction in order to collaborate in the project of an embedded electronic system for controlling and reading the information contained with the EMCCD. The technology of the electron multiplication in CCD devices and avalanche diodes has important applications in monitoring the environment of low light, astronomy and other scientific imaging applications including the low level of bioluminescence for the identification of drugs and applications of genetic engineering. For purposes of assessing the performance of the photo-detector it was necessary to develop an infrastructure to have proper control of the operating temperature of the EMCCD. Options were named with a montage of Peltier cell cooling and a choice of cryogenically cooled with liquid nitrogen. The results are useful in the detection of ultra weak light signals while minimizing detector noise during the acquisition of images from instrument comprising an optical tunable filter, that will be integrated into SOAR 4 meters telescope, installed in Chile, for observations improved with adaptive optics.

Dispositifs photovoltaïques d'aujourd'hui convertissent l'énergie solaire en électricité de manière propre, renouvelable et inépuisable et représentent un remplacement possible pour les combustibles fossiles. Toutefois, afin de rivaliser avec les sources d'énergie classiques une augmentation significative de l'efficacité de conversion est inévitable. Dans ce travail, nous nous concentrons sur des aspects pouvant propulser le rendement de conversion au-dessus des limites de cellules présentes. La première partie de l'étude est consacrée à de nouvelles idées théoriques considérés comme le photovoltaïque de 3ème génération, alors que le plus d'intérêt est maintenu à étudier les avantages possibles de la multiplication d'électrons faible seuil. Dans la deuxième partie de l'étude, nous développons un modèle qui permet un traitement précis des propriétés optiques et de transport des structures de silicium avec des interfaces enterrées. Les analyses théoriques et expérimentales approfondies des structures existantes MIND sont ensuite effectuées. En étudiant le flux exacte et la distribution d'énergie à l'intérieur de plusieurs structures dans le cadre de leur géométrie, nous estimons les rendements quantiques possibles et les comparer avec les résultats expérimentaux. Grâce aux moyens de simulations numériques couplées avec caractérisation expérimentale, nous extrayons l'efficacité de la collecte de porteur de cellules étudiées. De nouveaux effets sont observés, une telle augmentation possible de l'efficacité de la collecte au-dessus de l'unité. Une analyse plus approfondie des résultats expérimentaux couplés avec l'étude numérique suit quelques explications classiques et non classiques de l'augmentation de l'efficacité de la collecte ou l'augmentation résultante de l'efficacité quantique. Avec la plupart des explications classiques exclu, nous concluons que l'explication la plus probable, mais non définitive de cet effet peut être interprété comme le résultat d'une multiplication des porteurs faible seuil. / Photovoltaic devices of today convert solar energy into electricity in a clean, renewable and inexhaustible way and represent a possible replacement for the fossil fuels. However, in order to compete with classical energy sources a significant increase in the conversion efficiency is inevitable. In this work, we concentrate on the aspects able to raise the conversion efficiency above the limitations of present cells. The first part of the study is devoted to new theoretical ideas considered as 3rd generation photovoltaics, while the most interest is kept at studying the possible benefits of electron multiplication at low-energies. In the second part of the study, we develop a model that allows a precise treatment of optical and transport properties of silicon structures with buried interfaces. Extensive theoretical and experimental analyses of existing MIND structures are then conducted. By studying the exact flux and power distribution inside several structures in conjunction with their geometry, we estimate the possible quantum efficiencies and compare them with experimental results. Through the means of numerical simulations coupled with experimental characterization, we extract the carrier collection efficiency of studied cells. New effects are being observed, such a possible increase in collection efficiency above unity. A deeper analysis of the experimental results coupled with the numerical study analyzes several classical and non-classical explanations of the increase in collection efficiency or the resulting increase in the quantum efficiency. With most of the classical explanations ruled out, we conclude that the most probable, but not definitiveexplanation of this effect can be interpreted as the result of a low-energy carrier multiplication.

This degree project was performed in collaboration with the division of nuclear physics at the department of physics, KTH Royal Institute of Technology. A partial goal of the project was to create a simulation model, where the relationship be- tween the multiplication of electrons that occurs in an ionization chamber and the different pressures of air in the detector could be visualized. The main goal was then to use this model in order to examine the behaviour of electron multiplication for different geometries of the simulated ionization chamber. The simulation was performed in Python 3.7 (Python Soft- ware Foundation, DE, United States), and geometry was modified by increasing and decreasing the simulated inner and anode wire radius of the chamber. Results showed that the peak of the multiplication curve occurred at different pressures for different geometries. When the anode wire radius was fixed, the peak occurred at a lower pressure for an increase of the inner radius, whereas, when the inner radius was fixed, the peak occurred at a higher pressure for an increase of the anode wire radius. The number of created electrons are dependent of Townsend’s coefficent, α, which in turn is dependent of the relationship between pressure and electric field strength. The electric field strength within an ionization chamber varies for different geometries, and therefore is the relationship between pressure and electric field that results in the max- imum value of α, and thus the maximum peak of the multiplication factor, consequently given by different pressures for different chamber geometries. If the results from the simulations in this project are to correspond with actual experimental data, the knowledge of this geometry-dependence may be used to include or exclude the multiplication peak in further measurements depending upon preference.