The growth in global demand for energy, a significant emission of pollutants into the atmosphere and related concerns about the environmental impact of fossil fuels led to an awareness on the use of high sustainability alternatives. One of the possible solutions is given by thin film organic photovoltaics (OPV), developed in the past few years exclusively on a lab scale, because not ready for up-scaling processes, yet. One of the causes is related to the limits of efficiency in single-junction devices. My thesis aims the realization of multi-junction devices, known as tandem, which present greater efficiency than the corresponding single-junction solar cells at the same thickness. With the characterization of adhesion, morphological and optical properties the inks/formulations used in this work were characterized. This was useful to understand their compatibility for the manufacture of organic solar cells on flexible substrates. A preliminary study on opto-electronic properties of the materials was occurred through the realization of single-junction devices on rigid substrates, using the spin coating technique, and the best conditions were transferred to flexible substrates using the technique slot die coating. Subsequently tandem organic solar cells with two junctions electrically connected in series were manufactured on both substrates. An optical model in transfer matrix (TMF) was used to understand the influence of the electric field on the photo-generation process of charge in devices experimentally realized. It was also possible to assess how the density of the short circuit current (JSC) varies depending on the thickness of the active layer and to build theoretical tandem structures with the best results obtained from the calculation.
La crescente richiesta energetica mondiale, l’emissione rilevante di inquinanti in atmosfera e le correlate preoccupazioni sull’impatto ambientale delle fonti fossili hanno portato a una sensibilizzazione sull’impiego di alternative ad alta sostenibilità. Una delle soluzioni possibili è data dal fotovoltaico organico a film sottile (OPV), sviluppatosi negli ultimi anni esclusivamente su scala di laboratorio e non ancora maturo per uno scale-up industriale. Una delle cause è legata ai limiti di efficienza nei dispositivi a singola giunzione. Il mio lavoro di tesi si pone come obiettivo la realizzazione di dispositivi a giunzione multipla, noti come tandem, che presentino efficienza maggiore rispetto ai relativi dispositivi a singola giunzione, a parità di spessore. Grazie alla caratterizzazione delle proprietà di adesione, morfologiche e ottiche è stato possibile definire se le formulazioni impiegate possiedano i requisiti necessari per la fabbricazione di celle solari organiche su supporto flessibile. Lo studio preliminare delle proprietà opto-elettroniche dei materiali è avvenuto attraverso la realizzazione di dispositivi a singola giunzione su supporto rigido mediante spin coating, e le condizioni migliori sono state trasferite su supporto flessibile mediante slot die coating. Successivamente sono stati realizzati su entrambe le tipologie di substrato i dispositivi tandem, aventi due giunzioni connesse elettricamente in serie. L’impiego di un modello ottico a matrice di trasferimento (TMF) ha permesso di comprendere l’influenza del campo elettrico sulla fotogenerazione di carica nei dispositivi realizzati sperimentalmente. È stato possibile inoltre valutare come la densità di corrente di corto circuito (JSC) varia in funzione dello spessore di strato attivo e di costruire dispositivi tandem teorici con i risultati migliori ottenuti dal calcolo.
Preparazione e caratterizzazione di celle solari organiche ad architettura tandem
BARBIERI, RICCARDO
2014/2015
Abstract
The growth in global demand for energy, a significant emission of pollutants into the atmosphere and related concerns about the environmental impact of fossil fuels led to an awareness on the use of high sustainability alternatives. One of the possible solutions is given by thin film organic photovoltaics (OPV), developed in the past few years exclusively on a lab scale, because not ready for up-scaling processes, yet. One of the causes is related to the limits of efficiency in single-junction devices. My thesis aims the realization of multi-junction devices, known as tandem, which present greater efficiency than the corresponding single-junction solar cells at the same thickness. With the characterization of adhesion, morphological and optical properties the inks/formulations used in this work were characterized. This was useful to understand their compatibility for the manufacture of organic solar cells on flexible substrates. A preliminary study on opto-electronic properties of the materials was occurred through the realization of single-junction devices on rigid substrates, using the spin coating technique, and the best conditions were transferred to flexible substrates using the technique slot die coating. Subsequently tandem organic solar cells with two junctions electrically connected in series were manufactured on both substrates. An optical model in transfer matrix (TMF) was used to understand the influence of the electric field on the photo-generation process of charge in devices experimentally realized. It was also possible to assess how the density of the short circuit current (JSC) varies depending on the thickness of the active layer and to build theoretical tandem structures with the best results obtained from the calculation.| File | Dimensione | Formato | |
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2015_12_Barbieri.pdf
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Descrizione: Testo della tesi
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https://hdl.handle.net/10589/115424