Melissa Ann Davis

Nickel oxide (NiO _x ) is a common hole transport layer (HTL) in perovskite photovoltaics, but the chemical reactivity of NiOx surfaces accelerates degradation when contacting perovskites. We developed an ultrathin, conformal tin oxide (SnO _x ) interlayer to suppress interfacial reactivity between NiO _x and perovskite. SnO _x is typically an electron transport layer, but we show that the energy alignment can be modified for hole extraction using molecules with dipoles. This synergy yielded high efficiency in perovskite photovoltaic devices and showed an ~10x improvement in T 90 lifetime in open-circuit conditions under AM1.5G at 65°C. This structure also improves resilience to thermomechanical durability, as minimodules retained 95.7% of their initial performance after 1000 thermal cycles (−65° to 85°C), highlighting the importance of interfaces for robust perovskite photovoltaic modules.

Current encapsulation architectures for thin‐film metal halide perovskite do not adequately eliminate all ambient stressors. Here, we develop low transmission rate barrier layers using atomic layer deposited (ALD) aluminum oxide grown directly on the completed photovoltaic (PV) device stack to provide an additional seal, prior to full packaging. We investigate the effect of deposition temperature and oxidant chemistries on the barrier growth for protection of perovskite photovoltaic devices. We characterize the layers individually, then integrate into devices to detail the tradeoff between protection and deposition compatibility. To enhance compatibility and impermeability, we present an approach using water as the aluminum oxidant during nucleation and switching from water to ozone for the remainder of the growth. At 50 nm, the barrier results in a water vapor transmission rate (WVTR) of 4.5·10 ⁻⁴ g/m ² /day, and 1,000‐hour device stability under 45°C with 85% relative humidity without further packaging. This barrier provides sufficient protection to enable minimal degradation of the perovskite solar cells while completely submerged in water for 140 minutes. Additionally, we characterize the oxygen transmission rate (OTR) to be 0.49 cm ³ /m ² /day at 23°C and 0% relative humidity, which is 1.5 orders of magnitude improvement over the OTR of the current encapsulation.

Here, a thorough study of the effects of multiple stressors on a series of FAMACsPb(IBr)3 solar cells was assessed to test the stability of such systems for space applications. Combinations of thermal cycling, constant illumination, and electric field during the temperature ramp were all investigated. In all cases, some degradation of the solar cells was apparent, which was nearly reversible in the case of protocol 1 (thermal) and protocol 2 (thermal with illumination). However, under protocols 3 and 4 (thermal, illumination, and variable electric field), the devices did not return to initial conditions, suggesting possible irreversible degradation. An evaluation of device parameters: short circuit current density (Jsc), fill factor (FF), and open circuit voltage (Voc) shows that the Jsc is the least affected parameter [T = 450 K, remaining factors Jsc(T)/Jsc(300 K) ≥ 94%] regardless of protocol. For all protocols, the remaining factors at T = 450 K were 85%–90% and 78%–85% for FF and Voc, respectively. Under protocol 4 (practical solar cell operation), the FF and Voc behavior lags behind that of protocols 1 and 2 until T > 420 K. Overall, the results indicate that metal halide perovskite solar cells have potential for space power applications, as the device’s remaining factors were ≥90% for protocols 4, 2, and 1 for T ≤ 380, 400, and 420 K, respectively. With regard to CubeSat missions testing metal halide perovskites by applying a controlled voltage (V = 0.001 V) between measurements (protocol 2), particularly when the device is idle, degradation from combined stressors can be mitigated, reducing the risk of irreversible damage.

Robust contact schemes that boost stability and simplify the production process are needed for perovskite solar cells (PSCs). We codeposited perovskite and hole-selective contact while protecting the perovskite to enable deposition of SnO _x /Ag without the use of a fullerene. The SnO _x , prepared through atomic layer deposition, serves as a durable inorganic electron transport layer. Tailoring the oxygen vacancy defects in the SnO _x layer led to power conversion efficiencies (PCEs) of >25%. Our devices exhibit superior stability over conventional p-i-n PSCs, successfully meeting several benchmark stability tests. They retained >95% PCE after 2000 hours of continuous operation at their maximum power point under simulated AM1.5 illumination at 65°C. Additionally, they boast a certified T ₉₇ lifetime exceeding 1000 hours.

Flexible perovskite solar cells introduce opportunities for high throughput, high specific weight, and short energy payback time photovoltaics. However, they require additional investigation into their mechanical resiliency. This work investigates the mechanical properties and behaviors of perovskite thin films and builds a robust model for future research. A two-pronged approach was utilized. Perovskite thin films were flexed in a three-point bend mode with in-situ SEM. Novel insights into the perovskite mechanical behaviors with varying substrate layers were gained. Modeling and validation, the second prong, was completed with finite element analysis. Model coupons of the imaged perovskite architectures were built, with sensitivity analysis completed to provide mechanical property estimates. The results demonstrate that mechanical degradation of perovskite thin films on polyethylene terephthalate (PET) primarily presents as a crack in the grain boundaries between crystals. Perovskite thin films on Indium Tin Oxide (ITO) and PET primarily crack in a periodic pattern regardless of the placement of perovskite crystals.

Cracking behaviors within perovskite thin films are modeled through finite element analysis. Coupons of polyethylene terephthalate (PET), Indium Tin Oxide (ITO), and perovskite layers are deformed in three-point bend mode. Modeling gives insight into ranges for the physical properties of each layer due to gaps in literature inputs. The model proves the relationship between perovskite crystal size and its mechanical tolerance. Models with smaller crystals withstand more than 30% further displacement than those with crystals twice their size. A material replacement of ITO, the driving force causing cracking in films, is also modeled, and cracking within the perovskite layer occurred significantly later, showing an improved resilience to bending.