Perovskite solar cells (PSCs) are promising photovoltaic technologies, since they are fabricated from unexpensive materials, by means of low-energy processes, and exhibit high photovoltaic conversion efficiency (PCE). PSCs are composed of a semiconductor active material, the perovskite, which is sandwiched between selective charge extracting materials. Generally, electrodes consist in a thin metal film and in a transparent conductive oxide. The accurate selection of each component of the solar cell is crucial to achieve high PCEs because a correct energy level alignment within the device results in efficient charge transport processes. In this project, formamidium lead iodide perovskite (FAPbI3) was elected as active material, because of its suitable bandgap energy and its convenient structural properties. Tin oxide (SnO2) and Spiro-OMe-TAD were employed as electron transporting material (ETM) and hole transporting material (HTM) respectively. Thin films of gold and indium tin oxide (ITO) formed the electrodes of the solar cells. Fabricated PSCs were optimised through interface and bulk engineering. Methylammonium chloride (MACl) was employed to hinder phase transition from the perovskite α-FAPbI3 to the non-perovskite δ-FAPbI3. Moreover, a low-dimensional perovskite, of formula BA(2)FA(n-1)Pb(n)I(3n+1), was formed on top of FAPbI3, producing a bilayer structure and enhancing the PCE of the solar cell. For the deposition of the ETM, several annealing temperatures, spin-coating procedures and SnO2 concentrations in water were investigated. Two recipes were examined for the HTM and additional treatments to the layer were attempted to enhance the performances of the cells. Eventually, a standard fabrication method was determined for the production of highly efficient PSCs, characterised by remarkable photovoltaic parameters, achieving 20.39% PCE. Finally, BA(2)FA(n-1)Pb(n)I(3n+1) perovskite was substituted with a passivation layer produced by depositing a solution of 4-methylphenethylammonium chloride (4-MePEACl) onto FAPbI3, ultimately enhancing the PCE of the solar cells to 21.37%.
Le celle solari a perovskite (PSC) sono promettenti tecnologie fotovoltaiche, dato che sono prodotte con materiali economici, attraverso processi a basso impatto energetico, e generano elevate efficienze di conversione fotovoltaica (PCE). Le PSC sono costituite da un materiale attivo semiconduttore, la perovskite, che è interfacciato a due materiali trasportatori selettivi di carica che, a loro volta, si trovano a contatto con gli elettrodi della cella, tipicamente un metallo e un ossido trasparente conduttivo. Al fine di produrre elevate PCE, è fondamentale favorire un ottimale processo di estrazione di carica nel dispositivo, selezionando accuratamente ciascun componente. In questo progetto, la perovskite formammidinio piombo ioduro (FAPbI3) è stata scelta come materiale attivo, date la sua adeguata energia di band gap e le sue notevoli proprietà strutturali. Ossido di stagno (SnO2) e Spiro-OMe-TAD sono stati utilizzati, rispettivamente, come materiale trasportatore di elettroni (ETM) e materiale trasportatore di lacune (HTM) e un film nanometrico di oro e uno strato di ossido di indio drogato con stagno (ITO) sono stati impiegati come elettrodi. Con l’obiettivo di raggiungere performance significative, ciascuno strato del dispositivo è stato ottimizzato, destinando particolare attenzione ai singoli materiali e alle interfacce tra strati adiacenti. Cloruro di metilammonio (MACl) è stato adoperato per impedire la transizione di fase da α-FAPbI3 a δ-FAPbI3, rispettivamente fase perovskitica e non-perovskitica. Inoltre, una perovskite a bassa dimensionalità, di formula BA(2)FA(n-1)Pb(n)I(3n+1), è stata sintetizzata sulla superficie di FAPbI3, producendo una struttura a doppio strato ed aumentando la PCE delle celle solari. Per la formazione dell’ETM sono state testate diverse temperature di annealing, procedure di spin-coating e concentrazioni di SnO2 in acqua. Per quanto riguarda l’HTM, sono state confrontate due diverse ricette e valutati svariati trattamenti del film. Considerando i risultati ottenuti, è stata definita una procedura di fabbricazione, che ha portato alla creazione di PSC caratterizzate da parametri fotovoltaici considerevoli, raggiungendo PCE pari a 20.39%. Infine, la perovskite BA(2)FA(n-1)Pb(n)I(3n+1) è stata sostituita con uno strato di passivazione, generato depositando una soluzione di cloruro di 4-metilfeniletilammonio (4-MePEACl) su FAPbI3, che ha permesso di incrementare la PCE delle PSC fino a 21.37%.
Ingegnerizzazione di Materiali ed Interfacce in Celle Solari a Perovskite Formammidinio Piombo-Alogenuro: una via verso Dispositivi ad Alta Efficienza
LARINI, VALENTINA
2020/2021
Abstract
Perovskite solar cells (PSCs) are promising photovoltaic technologies, since they are fabricated from unexpensive materials, by means of low-energy processes, and exhibit high photovoltaic conversion efficiency (PCE). PSCs are composed of a semiconductor active material, the perovskite, which is sandwiched between selective charge extracting materials. Generally, electrodes consist in a thin metal film and in a transparent conductive oxide. The accurate selection of each component of the solar cell is crucial to achieve high PCEs because a correct energy level alignment within the device results in efficient charge transport processes. In this project, formamidium lead iodide perovskite (FAPbI3) was elected as active material, because of its suitable bandgap energy and its convenient structural properties. Tin oxide (SnO2) and Spiro-OMe-TAD were employed as electron transporting material (ETM) and hole transporting material (HTM) respectively. Thin films of gold and indium tin oxide (ITO) formed the electrodes of the solar cells. Fabricated PSCs were optimised through interface and bulk engineering. Methylammonium chloride (MACl) was employed to hinder phase transition from the perovskite α-FAPbI3 to the non-perovskite δ-FAPbI3. Moreover, a low-dimensional perovskite, of formula BA(2)FA(n-1)Pb(n)I(3n+1), was formed on top of FAPbI3, producing a bilayer structure and enhancing the PCE of the solar cell. For the deposition of the ETM, several annealing temperatures, spin-coating procedures and SnO2 concentrations in water were investigated. Two recipes were examined for the HTM and additional treatments to the layer were attempted to enhance the performances of the cells. Eventually, a standard fabrication method was determined for the production of highly efficient PSCs, characterised by remarkable photovoltaic parameters, achieving 20.39% PCE. Finally, BA(2)FA(n-1)Pb(n)I(3n+1) perovskite was substituted with a passivation layer produced by depositing a solution of 4-methylphenethylammonium chloride (4-MePEACl) onto FAPbI3, ultimately enhancing the PCE of the solar cells to 21.37%.È consentito all'utente scaricare e condividere i documenti disponibili a testo pieno in UNITESI UNIPV nel rispetto della licenza Creative Commons del tipo CC BY NC ND.
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https://hdl.handle.net/20.500.14239/14029