Sinteza organsko-anorganskih hibridnih halogenid perovskitov

magistrsko delo

Barbara Repič (Author), Marjan Marinšek (Mentor), Urška Šebenik (Thesis defence commission member), Boštjan Genorio (Thesis defence commission member)

Abstract

Med nastajajočimi fotovoltaičnimi tehnologijami je veliko pozornosti namenjene perovskitnim sončnim celicam. Presenetile so z neverjetno hitrim izboljšanjem učinkovitosti, ki je iz 2% v letu 2006 zrastla na več kot 20% v letu 2015. Poleg razpoložljivosti surovin je njihova nabavna vrednost nižja od običajnih silicijevih sončnih celic. Aktivna plast za absorpcijo svetlobe teh sončnih celic je 3D hibriden organsko-anorganski perovskitni material s kemijsko formulo ABX3. Ti materiali imajo izjemne lastnosti za fotovoltaične aplikacije kot so ustrezna širina prepovedanega pasu, visok absorpcijski koeficient, visoka mobilnost naboja in preprosto tvorbo plasti z nizkotemperaturni postopki nanašanja. Večinoma se v perovskitnih sončnih celicah uporablja metilamonijev svinčev halogenidni perovskit CH3NH3PbX3, X = Br, I. Tehnologija perovskitnih sončnih celic je kljub številnim izboljšavam še vedno v zgodnjih fazah komercializacije zaradi pomislekov glede stabilnosti in toksičnosti svinca. Za voljo tega se preučujejo tudi številne druge sestave organsko-anorganskih perovskitov. S spreminjanjem kationov in anionov se lahko enostavno spreminja kristalno strukturo in posledično tudi optične in elektronske lastnosti materiala. Smernice za izbor ionov z ustreznimi velikostmi radijev glede na kubično simetrijo, ki zagotavlja optimalne lastnosti za uporabo v fotovoltaiki, predstavljata tolerančni in oktaedrični faktor. V tem magistrskem delu se je na podlagi razpoložljivih podatkov iz literature najprej proučil sintezni postopek CH3NH3PbI3 perovskita. Sinteza poteka v dveh delih - s predhodno sintezo organskega halogenida, ki mu sledi mešanje le-tega z anorganskim halogenidom v ustreznem topilu. Z žarjenjem tako pripravljene prekurzorske raztopine se izkristalizira želen produkt. Ključni parametri pri sintezi so molarno razmerje reaktantov, izbor topila in vpliv vlage. CH3NH3PbI3 perovskit je nastal v treh različnih topilih - GBL, DMF in DMSO, s prisotnimi sekundarnimi fazami le v zadnjem primeru. Sinteza je bila uspešna tako pri stehiometrijskem razmerju reaktantov kot tudi pri uporabi pribitka PbI2. Na meritvah rentgenske praškovne difrakcije ni bilo vidnih razlik. Vse sinteze so bile opravile le pri atmosferskih pogojih. Po uspešni sintezi CH3NH3PbI3 se je na podlagi tolerančnih in oktaedričnih faktorjev izbralo še 24 spojin, ki v teoriji lahko tvorijo perovskitno kristalno strukturo. Za sintezo teh perovskitov se je uporabila prekurzorska raztopina v GBL s 40 ut.% reaktantov v stehiometrijskem razmerju. Večina izhodnih spojin je topnih v izbranem topilu z izjemo hidrazinijevega in imidazolijevega jodida ter vsi anorganski bromidi in kloridi. Za topnost PbI2 je bila potrebna prisotnost organskega halogenida. Sinteze želenih perovskitov so bile neuspešne v primeru neuspešne priprave reaktantov. Uporaba enakega sinteznega postopka za perovskite s hidrazinijevim ionom se je izkazala kot neuspešna, saj so nastali le amorfni in razgradni produkti. Podobno je bilo pri perovskitih, ki vsebujejo stroncij in kalcij. Sinteza bromidnih in kloridnih perovskitov je v nekaterih vzorcih bila uspešna kljub netopnosti reaktantov.

Keywords

materiali;perovskiti;perovskitne sončne celice;sinteza;hibridi;halogenidi;praškovna rentgenska difrakcija;XRD;magistrska dela;

Data

Language:	Slovenian
Year of publishing:	2019
Typology:	2.09 - Master's Thesis
Organization:	UL FKKT - Faculty of Chemistry and Chemical Technology
Publisher:	[B. Repič]
UDC:	620.1(043.2)
COBISS:	1538443715
Views:	770
Downloads:	196
Average score:	0 (0 votes)
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Other data

Secondary language:	English
Secondary title:	Synthesis of organic-inorganic hybrid halide perovskites
Secondary abstract:	Among the emerging photovoltaic technologies perovskite solar cells have attracted a great deal of attention. They surprised with incredibly rapid improvement in efficiency, which increased from 2% in 2006 to more than 20% in 2015. In addition to the availability of raw materials, their cost is lower than conventional silicon solar cells. The active light-absorbing layer of these solar cells is a 3D hybrid organic-inorganic perovskite material with chemical formula ABX3. These materials have exceptional properties for photovoltaic applications such as adequate bandgap, high absorption coefficient, high charge mobility and simple film formation with low-temperature deposition procedures. Perovskite solar cells predominantly use methylammonium lead halide perovskite CH3NH3PbX3, X = Br, I. Despite many improvements, the technology of perovskite solar cells is still in the early stages of commercialization due to lead stability and toxicity concerns. A number of other organic-inorganic perovskite compositions are also being studied because of that reason. By changing cations and anions, the crystal structure and consequently optical and electronic properties of this material can easily be altered. Tolerance and octahedral factors offer guidelines for the selection of ions with appropriate radius sizes according to cubic symmetry, which provides optimum properties for use in photovoltaics. In this master's thesis the synthesis process of CH3NH3PbI3 perovskite was researched based on the available literature data. The synthesis consists of two parts, the preliminary synthesis of the organic halide, followed by mixing the latter with the inorganic halide in the appropriate solvent. Annealing thus prepared precursor solutions results in crystallization of the desired product. The key parameters in the synthesis are the molar ratio of the reactants, the choice of solvent and the influence of moisture. CH3NH3PbI3 perovskite was formed in three different solvents - GBL, DMF in DMSO, with secondary phases only present in the later. The synthesis was successful both times, when using the stoichiometric ratio of the reactants as well as when using the excessive amounts of PbI2. There were no visible differences between XRD measurements. Syntheses were made only under atmospheric conditions. Following the successful synthesis of CH3NH3PbI3, other 24 compounds were selected, which in theory can form a perovskite crystal structure based on their tolerance and octahedral factors. For the synthesis of these perovskites a precursor solution in GBL with 40 wt% reactants in stoichiometric ratio was used. Most of the starting compounds are soluble in the selected solvent with the exception of hydrazinium and imidazolium iodide and all inorganic bromides and chlorides. For solubility of PbI2 addition of organic halide was required. The synthesis of the desired perovskites failed in case of unsuccessful preparation of reactants. The use of the same synthesis process for perovskites with hydrazinium ion proved to be unsuccessful, as only amorphous and the degradation products were observed. Similar results were observed in perovskites containing strontium and calcium. In some samples synthesis of bromide and chloride perovskites was successful regardless of insolubility of the reactants.
Secondary keywords:	synthesis;perovskite;hybride;XRD;
Type (COBISS):	Master's thesis/paper
Study programme:	1000376
Embargo end date (OpenAIRE):	1970-01-01
Thesis comment:	Univ. v Ljubljani, Fak. za kemijo in kemijsko tehnologijo, smer Kemijsko inženirstvo
Pages:	97 str.
ID:	11234437