Organisch-anorganische Perowskite sind attraktiv für Dünnschichtsolarzellen. Die Übertragung laborbasierter Herstellungsverfahren, typischerweise Rotationsbeschichtung, auf industrielle Prozesse erfordert ein tiefgehendes Verständnis der physikalisch-chemischen Auswirkungen auf die Schichtqualität. Diese Arbeit zeigt, dass die Effizienz-Reproduzierbarkeit von Perowskit-Solarzellen (PSCs) nicht primär durch Unterschiede zwischen Laboren, sondern durch interne Prozessschwankungen beeinflusst wird. Verglichen wurden PSCs mit PEDOT und PTAA als Lochleiter auf den beiden Perowskiten, MAPI und 3CAT. PEDOT-basierte PSCs zeigten neben geringerer Reproduzierbarkeit eine niedrigere Effizienz, bedingt durch Voc- und FF-Verluste, schlechtere energetische Angleichung und morphologische Grenzflächenprobleme. Im Vergleich zu 3CAT, war die Effizienz von MAPI-basierten Zellen schlechter reproduzierbar, was durch eine stärkere Abhängigkeit der MAPI-Schichten von Prozessschwankungen erklärt werden kann. Die Anwendung eines Anti-Lösungsmittel-Tropfens (AS-Tropfen) während des in dieser Rotationsbeschichtungsprozesses beeinflusst die Morphologie und Effizienz der Solarzellen erheblich. Das optimale Zeitfenster für den AS-Tropfen ist für MAPI (~10 s) kleiner als für 3CAT (~50 s). Ein falsches Timing führt zu morphologischen Hohlräumen und vermindert die Effizienz. Optische In-situ-Studien zeigten, dass der AS-Tropfen vor Beginn der natürlichen Perowskit-Kristallisation appliziert werden sollte. Für MAPI beginnt diese nach 20 Sekunden, für 3CAT nach 100 Sekunden. Ein zu später AS-Tropfen reduziert die Verfügbarkeit von Lösungsmittel für die Rekristallisation und verschlechtert die Morphologie der Perowskit-Phase. 3CAT toleriert zeitliche Variationen besser, da es während der natürlichen Kristallisation sowohl lösungsmittelhaltige Vorphasen als auch Perowskit-Phasen bildet, während MAPI hauptsächlich lösungsmittelhaltige Vorphasen bildet, was die Prozessanfälligkeit erhöht. / Organic-inorganic perovskites are promising materials for thin-film solar cells, with potential for industrial-scale production through scalable manufacturing. The transition from laboratory-based spin-coating to scalable processes requires understanding the factors affecting perovskite film quality. High-performance reproducibility is essential for commercializing perovskite solar cells (PSCs), currently challenging for certain perovskite combinations. Reproducibility issues are evident from performance variations in published PSC results fabricated from different laboratories. Even within a single laboratory, process fluctuations can lead to efficiency irreproducibility, as this study shows. Different PSC stack combinations were compared using two hole conductors, PEDOT and PTAA, with two perovskite compositions, MAPI and 3CAT. PEDOT solar cells showed low reproducibility and lower efficiency due to poor energetic alignment and morphological issues. MAPI and 3CAT with PTAA achieved higher efficiencies. However, MAPI is more sensitive to process variations, leading to lower reproducibility. This hypothesis is supported by in-situ measurements, which show that the timinng window for the addition of an anti-solvent drip (AS-drip) during spin-coating is narrower for MAPI (~10 s) than for 3CAT (~50 s). AS-drip outside this window causes morphological voids, reducing efficiency. The optical in-situ studies show that AS-drip timing is crucial: crystallization onset occurs earlier for MAPI (20s) than for 3CAT (100s). Late AS-drip results in solvate phase formation, reducing solvent availability and negatively impacting morphology. MAPI forms solvate exclusively during crystallization, while 3CAT forms both solvate and perovskite phases, increasing tolerance to timing variations.

No description available.

<p>  </p> <p>Organic-inorganic halide perovskites are at the brink of commercialization as the next generation of light-absorbing materials for solar energy harvesting devices. Perovskites have large absorption coefficients, long charge-carrier lifetimes and diffusion lengths, and a tunable absorption spectrum. Furthermore, these materials can be low-temperature solution-processed, which transfers to low-cost manufacturing and cost-competitive products. The remarkable material properties of perovskites enable a broad product-market fit, encompassing traditional and new applications for solar technology. Perovskites can be deposited on flexible substrates for flexible solar cells, applied in thermochromic windows for power generation and building cooling, or tuned for tandem solar cell application to include in high-performance solar panels. However, perovskites are intrinsically unstable, which has so far prevented their commercialization. Despite large research efforts, including over two thousand publications per year, perovskite solar cells degrade in under one year of operation. In a saturated research field, new ideas are needed to inspire alternative approaches to solve the perovskite stability problem. In this dissertation, we detail research efforts surrounding the concept of a self-healing perovskite solar cell.</p> <p>     A self-healing perovskite solar cell can be classified with two distinctions: mechanically healing and molecularly healing. First, mechanically self-healing involves the material’s ability to recover its intrinsic properties after mechanical damage such as tares, lacerations, or cracking. This type of healing was unique to the organic polymer community and ultra-rare in semiconducting materials. By combining a self-healing polymer with perovskite material, we developed a self-healing semiconducting perovskite composite material which can heal using synergistic grain growth and solid-state diffusion processes at slightly elevated temperatures. The material is demonstrated in flexible solar cells with improved bending durability and a power conversion efficiency reaching 10%. The addition of fluidic polymer enables macroscopic perovskite material movement, which is otherwise brittle and rigid. The results inspire the use of polymer scaffolds for mechanically self-healing solar cells.</p> <p>     The second type of healing, molecular healing, involves healing defects within the rigid crystal domains resulting from ion migration. The same phenomenon which leads to device degradation, also assists the recovery of the device performance after resting the device in the dark. During device operation, perovskite ions diffuse in the perovskite lattice and accumulate at the device interfaces where they undergo chemical reactions or leave the perovskite layer, ultimately consuming the perovskite precursors. The photovoltaic performance can be recovered if irreversible degradation is limited. Ideally, degradation and recovery can match day and night cycling to dramatically extend the lifetime of perovskite solar cells. In this dissertation, we introduce the application of chalcogenide chemistry in the fabrication of perovskite solar cells to control the thin film crystallization process, ultimately to reduce defects in the perovskite bulk and introduce surface functionality which extends the device stability. This new strategy will help improve molecularly self-healing perovskite solar cell by reducing irreversible degradation. Lastly, we present a few other new ideas to inspire future research in perovskite solar cells and assist in the commercialization of the next generation of photovoltaics.</p>