Gas-assisted spray coating of perovskite solar cells incorporating sprayed self-assembled monolayers

Self-assembled monolayers (SAMs) are becoming widely utilized as hole-selective layers in high-performance p-i-n architecture perovskite solar cells. Ultrasonic spray coating and airbrush coating are demonstrated here as effective methods to deposit MeO-2PACz; a carbazole-based SAM. Potential dewetting of hybrid perovskite precursor solutions from this layer is overcome using optimized solvent rinsing protocols. The use of air-knife gas-quenching is then explored to rapidly remove the volatile solvent from an MAPbI3 precursor film spray-coated onto an MeO-2PACz SAM, allowing fabrication of p-i-n devices with power conversion efficiencies in excess of 20%, with all other layers thermally evaporated. This combination of deposition techniques is consistent with a rapid, roll-to-roll manufacturing process for the fabrication of large-area solar cells

A flexible back-contact perovskite solar micro-module

Back-contact perovskite solar cells are fabricated by depositing methylammonium lead iodide perovskite into micron-sized grooves, with opposite walls of each groove being coated with either n- or p-type selective contacts. V-Shaped grooves are created by embossing a polymeric substrate, with the different charge-selective electrodes deposited onto the walls of the groove using a directional evaporation technique. We show that individual grooves act as photovoltaic devices, having a power conversion efficiency of up to 7.3%. By series-connecting multiple grooves, we create integrated micro-modules that build open circuit voltages up to nearly 15 V and power conversion efficiencies over 4%. The devices created are fully flexible, do not include rare metals, and are processed using techniques applicable to roll-to-roll processing

Manipulating Crystallization of Organolead Mixed-Halide Thin Films in Antisolvent Baths for Wide-Bandgap Perovskite Solar Cells

Wide-bandgap perovskite solar cells (PSCs) based on organolead (I, Br)-mixed halide perovskites (e.g., MAPbI₂Br and MAPbIBr₂ perovskite with bandgaps of 1.77 and 2.05 eV, respectively) are considered as promising low-cost alternatives for application in tandem or multijunction photovoltaics (PVs). Here, we demonstrate that manipulating the crystallization behavior of (I, Br)-mixed halide perovskites in antisolvent bath is critical for the formation of smooth, dense thin films of these perovskites. Since the growth of perovskite grains from a precursor solution tends to be more rapid with increasing Br content, further enhancement in the nucleation rate becomes necessary for the effective decoupling of the nucleation and the crystal-growth stages in Br-rich perovskites. This is enabled by introducing simple stirring during antisolvent-bathing, which induces enhanced advection transport of the extracted precursor-solvent into the bath environment. Consequently, wide-bandgap planar PSCs fabricated using these high quality mixed-halide perovskite thin films, Br-rich MAPbIBr₂, in particular, show enhanced PV performance

High-Performance Formamidinium-Based Perovskite Solar Cells via Microstructure-Mediated δ‑to‑α Phase Transformation

The δ → α phase transformation is a crucial step in the solution-growth process of formamidinium-based lead triiodide (FAPbI₃) hybrid organic–inorganic perovskite (HOIP) thin films for perovskite solar cells (PSCs). Because the addition of cesium (Cs) stabilizes the α phase of FAPbI₃-based HOIPs, here our research focuses on FAPbI₃(Cs) thin films. We show that having a large grain size in the δ-FAPbI₃(Cs) non-perovskite intermediate films is essential for the growth of high-quality α-FAPbI₃(Cs) HOIP thin films. Here grain coarsening and phase transformation occur simultaneously during the thermal annealing step. A large starting grain size in the δ-FAPbI₃(Cs) thin films suppresses grain coarsening, precluding the formation of voids at the final α-FAPbI₃(Cs)–substrate interfaces. PSCs based on the interface void-free α-FAPbI₃(Cs) HOIP thin films are much more efficient and stable in the ambient atmosphere. This interesting finding inspired us to develop a simple room-temperature aging method for preparing coarse-grained δ-FAPbI₃(Cs) intermediate films, which are subsequently converted to coarse-grained, high-quality α-FAPbI₃(Cs) HOIP thin films. This study highlights the importance of microstructure meditation in the processing of formamidinium-based PSCs

Autonominen videokuvan siirtoon soveltuva tietoverkkoratkaisu viranomaisajoneuvoihin

Työn tavoitteena oli luoda tutkielma, jossa huomioidaan olosuhteita ja tilanteita, joita voi tulla eteen videokuvan siirrossa kenttäolosuhteissa. Kenttäolosuhteissa toimittaessa on yhteyksien toimivuusvarmuuteen kiinnitettävä erityistä huomiota. Toimivista tietoliikenneyhteyksistä saattaa olla kiinni ihmishenkien tai materiaalien pelastuminen. Insinöörityössä tutkittiin eri kuvansiirtotapoja viranomaisajoneuvojen välillä. Työssä tutkittiin neljää erilaista tiedonsiirtotapaa, kahta kaapelitoteutusta ja kahta langatonta versiota. Tutkimus oli luonteeltaan teoreettinen, lukuun ottamatta WLAN mittauksia. Työssä pohditaan pääsääntöisesti erinäisiä ratkaisuja ja toteutustapoja. Langattoman lähiverkon (WLAN) toimivuus kenttäolosuhteissa on sidoksissa moneen käyttäjästä riippumattomaan asiaan kuten säähän, rakenteisiin ja maaston muotoihin. Tästä syystä langatonta lähiverkkoa ei voida pitää ensisijaisena tiedonsiirtomuotona. Tätä asiaa tukivat myös suoritetut mittaukset. WLAN:ia voidaan kuitenkin käyttää muodostettaessa verkko ajoneuvon lähietäisyydelle esimerkiksi kameraa tai tietokonetta varten. Työssä tutkittiin kotimaisen Ajeco Oy:n 4Com -monikanavareitittimen ominaisuuksia ja todettiin sen soveltuvan hyvin viranomaisajoneuvon kuvansiirron runkolaitteeksi. Johtopäätöksenä voidaan todeta, että kaapeliyhteydet ovat tiedonsiirto-ominaisuuksiltaan varmempia kuin langattomat vaihtoehdot. Kaapeliyhteyksien käyttökuntoon saattaminen on kuitenkin hitaampaa. Mahdollisissa jatkotutkimuksissa olisi huomioitava pidemmän matkan langattomien tiedonsiirtotapojen, kuten esimerkiksi WIMAXin, käyttömahdollisuuksia.This thesis aims to describe the effects of field operations on video transmission. Under field conditions, the functionality of data communications requires special attention. Problems in data connections may lead to material losses and in the worst case prevent saving human lives. The thesis examines different methods of transferring image between two vehicles. In detail, four different data transmission methods are compared; two cable implementations and two wireless versions. Problems and challenges are approached from a theoretical aspect. Specific implementation solutions are compared and their strengths and weaknesses are demonstrated. There are numerous different aspects that affect wireless LAN (WLAN) performance in field conditions. These aspects include the weather, infrastructure and terrain. For this reason, a wireless LAN cannot be considered as the primary option for video transmission. These concerns were proven justified via attenuation measurements of the WLAN signal. Nevertheless, WLAN may be used in forming a close range network around the vehicle, for example to connect cameras, computers and PDAs. For longer range video transfer it could be determined that a domestic Ajeco Ltd 4Com multi-channel router is an adequate device. It can be concluded that in order to provide stable, reliable and secure data transfer between vehicles, it is necessary to use wired connections. Wired connections are slower to setup than wireless connections, but wired connections are clearly a better choice due to the numerous challenges that are encountered with wireless connections. For future research it would be worthwile to study the possibilities of long-distance wireless communication methods such as Wi-MAX

Nonplanar spray-coated perovskite solar cells

Spray coating is an industrially mature technique used to deposit thin films that combines high throughput with the ability to coat nonplanar surfaces. Here, we explore the use of ultrasonic spray coating to fabricate perovskite solar cells (PSCs) over rigid, nonplanar surfaces without problems caused by solution dewetting and subsequent "run-off". Encouragingly, we find that PSCs can be spray-coated using our processes onto glass substrates held at angles of inclination up to 45° away from the horizontal, with such devices having comparable power conversion efficiencies (up to 18.3%) to those spray-cast onto horizontal substrates. Having established that our process can be used to create PSCs on surfaces that are not horizontal, we fabricate devices over a convex glass substrate, with devices having a maximum power conversion efficiency of 12.5%. To our best knowledge, this study represents the first demonstration of a rigid, curved perovskite solar cell. The integration of perovskite photovoltaics onto curved surfaces will likely find direct applications in the aerospace and automotive sectors

Direct integration of perovskite solar cells with carbon fiber substrates

Integrating photovoltaic devices onto the surface of carbon-fiber-reinforced polymer substrates should create materials with high mechanical strength that are also able to generate electrical power. Such devices are anticipated to find ready applications as structural, energy-harvesting systems in both the automotive and aeronautical sectors. Here, the fabrication of triple-cation perovskite n–i–p solar cells onto the surface of planarized carbon-fiber-reinforced polymer substrates is demonstrated, with devices utilizing a transparent top ITO contact. These devices also contain a “wrinkled” SiO2 interlayer placed between the device and substrate that alleviates thermally induced cracking of the bottom ITO layer. Devices are found to have a maximum stabilized power conversion efficiency of 14.5% and a specific power (power per weight) of 21.4 W g−1 (without encapsulation), making them highly suitable for mobile power applications.</p