Self-encapsulated wearable perovskite photovoltaics via lamination process and its biomedical application

Achieving over 20 % Efficiency in Laminated HTM-Free Carbon Electrode Perovskite Solar Cells through In Situ Interface Reconstruction

Laminating a free-standing carbon electrode film onto perovskite film is a promising method for fabricating HTM (hole transport material)-free carbon electrode perovskite solar cells (c-PSCs), offering more flexibility by decoupling the processes of carbon electrode and perovskite layer formation. However, the power conversion efficiency (PCE) of laminated HTM-free c-PSCs (<16.5 %) remains lower compared to c-PSCs with printed carbon pastes (>20 %), primarily due to poor interfacial contact between the perovskite and carbon layers. Herein, we report a chemical-mechanical driven in situ interface reconstruction strategy to solve such interface contact issues. The in situ interface reconstruction is firstly triggered by methylammonium chloride (MACl) surface treatment to chemically activate the film and then mechanically laminate the carbon electrode onto the softened perovskite film under heating. The perovskite film undergoes in situ regrowth and the carbon film starts to cure simultaneously, dynamically reconstructing the perovskite/carbon electrode interface. A tighter and conformal contact is achieved, greatly facilitating the carrier transport and extract. Ultimately, a champion PCE of 20.31 % is achieved with enhanced stability. Our in situ interface reconstruction strategy which is combinating the chemical and mechanical process offers a new choice for the further design of low-cost and efficient HTM-free c-PSCs.

Optimal bandgap of a single-junction photovoltaic cell for the mobile Internet-of-Things

The procedure for determining the maximum power of a single-junction photovoltaic cell operating in various types of lighting is presented. This is a key issue for photovoltaics powering the mobile Internet-of-Things (IoT). The simulations performed are based on the detailed balance principle, without any of the simplifying assumptions included in the Shockley-Queisser model. Optimal energy bandgap for diffuse solar light was found to be 1.64 eV with a cutoff generated power of 37.3 W/m2. For the LED lighting considered in this work, the optimal energy bandgap and maximum power limit are 1.86 eV, 1.63 W/m2, and 1.79 eV, 1.51 W/m2 for cool and warm lighting, respectively, at 900 lux. Considering that the maximum power limit of diffuse solar radiation is much higher than the limit for LED lighting, we concluded that 1.64 eV is the optimal bandgap for most mobile IoT devices operating outdoors all or almost all the time.

Understanding Process-Structure Relationships during Lamination of Halide Perovskite Interfaces

Fabrication of halide perovskite (HP) solar cells typically involves the sequential deposition of multiple layers to create a device stack, which is limited by the thermal and chemical incompatibility of top contact layers with the underlying HP semiconductor. One emerging strategy to overcome these restrictions on material selection and processing conditions is lamination, where two half-stacks are independently processed and then diffusion bonded to complete the device. Lamination reduces the processing constraints on the top side of the solar cell to allow new device designs, expanded use of deposition methods, and self-encapsulation of devices. While laminated perovskite solar cells with high efficiencies and novel interlayer combinations have been demonstrated, there is a limited understanding of how the lamination process parameters affect the diffusion-bond quality and material properties of the resulting HP layer. In this study, we systematically vary temperature, pressure, and time during lamination and quantify the resulting impacts on bonded area, grain domain size, and photoluminescence. A design of experiments is performed, and statistical analysis of the experimental results is used to quantitatively evaluate the resulting process-structure-property relationships. The lamination temperature is found to be the key parameter controlling these properties. A temperature of 150 °C enables successful bonding over 95% of the substrate area and also results in increases in apparent grain domain size and photoluminescence intensity. Based on these insights, the lamination temperature of functional perovskite solar cell devices is varied, demonstrating the importance of the resulting bond quality on device performance metrics.

Lamination of >21% Efficient Perovskite Solar Cells with Independent Process Control of Transport Layers and Interfaces

Transport layer and interface optimization is critical for improving the performance and stability of perovskite solar cells (PSCs) but is restricted by the conventional fabrication approach of sequential layer deposition. While the bottom transport layer is processed with minimum constraints, the narrow thermal and chemical stability window of the halide perovskite (HP) layer severely restricts the choice of top transport layer and its processing conditions. To overcome these limitations, we demonstrate lamination of HPs─where two transport layer-perovskite half-stacks are independently processed and diffusion-bonded at the HP-HP interface─as an alternative fabrication strategy that enables self-encapsulated solar cells. Power conversion efficiencies (PCE) of >21% are realized using cells that incorporate a novel transport layer combination along with dual-interface passivation via self-assembled monolayers, both of which are uniquely enabled by the lamination approach. This is the highest reported PCE for any laminated PSC encapsulated between glass substrates. We further show that this approach expands the processing window beyond traditional fabrication processes and is adaptable for different transport layer compositions. The laminated PSCs retained >75% of their initial PCE after 1000 h of 1-sun illumination at 40 °C in air using an all-inorganic transport layer configuration without additional encapsulation. Furthermore, a laminated 1 cm2 device maintained a Voc of 1.16 V. The scalable lamination strategy in this study enables the implementation of new transport layers and interfacial engineering approaches for improving performance and stability.