With rapid and brilliant progress in performance over recent years, perovskite solar cells have drawn increasing attention for portable power source applications.

By employing the neutral plane concept, we demonstrated ultra-flexible perovskite solar cells that can withstand 100 cycles of crumpling.

Black orthorhombic (B-γ) CsSnI3 with low toxicity and excellent optoelectronic properties is a promising candidate for perovskite solar cell (PSC). However, the performance of the B-γ CsSnI3-based PSCs is much lower than their lead-based or organotin-based counterparts due to the heavy self-doping of Sn2+ to form Sn4+ under ambient-air conditions. Here, this undesirable oxidation in CsSnI3 is restricted by engineering the localized electron density with phthalimide (PTM) additive. The lone electron pairs of NH and two CO units of PTM are designed to form trigeminal coordination bonding with Sn2+, resulting in reduced defect density and relatively grain-ordered perovskite film. The champion efficiencies of 10.1% and 9.6% are obtained for the modified rigid and flexible B-γ CsSnI3-based PSCs, respectively. These encapsulated devices maintain 94.3%, 83.4%, and 81.3% of their initial efficiencies under inert (60 days), ambient (45 days), and 1 Sun continuous illumination at ∼70 °C (2000 min) conditions, respectively.

Transparent carbon electrodes, carbon nanotubes, and graphene were used as the bottom electrode in flexible inverted perovskite solar cells. Their photovoltaic performance and mechanical resilience were compared and analyzed using various techniques. Whereas a conventional inverted perovskite solar cells using indium tin oxide showed a power conversion efficiency of 17.8%, the carbon nanotube- and graphene-based cells showed efficiencies of 12.8% and 14.2%, respectively. An established MoO doping was used for  carbon electrode-based devices. The difference in the photovoltaic performance between the carbon nanotube- and graphene-based cells was due to the difference in morphology and transmittance. Raman spectroscopy, and cyclic flexural testing revealed that the graphene-based cells were more susceptible to strain than the carbon nanotube-based cells, though the difference was marginal. Overall, despite higher performance, the transfer step for graphene has lower reproducibility. Thus, the development of better graphene transfer methods would help maximize the current capacity of graphene-based cells.

Solution processability of photoactive halide perovskites differentiates them from traditional inorganic semiconducting materials that require multiple post-processing steps such as thermal/vacuum/blow- & solvent-assistant treatment. Here we report a technical breakthrough...

Double‐walled carbon nanotubes are between single‐walled carbon nanotubes and multiwalled carbon nanotubes. They are comparable to single‐walled carbon nanotubes with respect to the light optical density, but their mechanical stability and solubility are higher. Exploiting such advantages, solution‐processed transparent electrodes are demonstrated using double‐walled carbon nanotubes and their application to perovskite solar cells is also demonstrated. Perovskite solar cells which harvest clean solar power have attracted a lot of attention as a next‐generation renewable energy source. However, their eco‐friendliness, cost, and flexibility are limited by the use of transparent oxide conductors, which are inflexible, difficult to fabricate, and made up of expensive rare metals. Solution‐processed double‐walled carbon nanotubes can replace conventional transparent electrodes to resolve such issues. Perovskite solar cells using the double‐walled carbon nanotube transparent electrodes produce an operating power conversion efficiency of 17.2% without hysteresis. As the first solution‐processed electrode‐based perovskite solar cells, this work will pave the pathway to the large‐size, low‐cost, and eco‐friendly solar devices.

Black orthorhombic (B-γ) CsSnI3 with reduced biotoxicity and environmental impact and excellent optoelectronic properties is being considered as a promising eco-friendly candidate for high-performing perovskite solar cells (PSCs). A major challenge in a large-scale implementation of CsSnI3 PSCs includes the rapid transformation of Sn2+ to Sn4+ (within a few minutes) under an ambient-air condition. Here, we demonstrate that ambient-air stable B-γ CsSnI3 PSCs can be fabricated by incorporating N,N′-methylenebis­(acrylamide) (MBAA) into the perovskite layer and by using poly­(3-hexylthiophene) as the hole transporting material. The lone electron pairs of −NH and −CO units of MBAA are designed to form coordination bonding with Sn2+ in the B-γ CsSnI3, resulting in a reduced defect (Sn4+) density and better stability under multiple conditions for the perovskite light absorber. After a modification, the highest power conversion efficiency (PCE) of 7.50% is documented under an ambient-air condition for the unencapsulated CsSnI3-MBAA PSC. Furthermore, the MBAA-modified devices sustain 60.2%, 76.5%, and 58.4% of their initial PCEs after 1440 h of storage in an inert condition, after 120 h of storage in an ambient-air condition, and after 120 h of 1 Sun continuous illumination, respectively.

A moth-eye nanostructured mp-TiO2 film using conventional lithography, nano-imprinting and polydimethyl-siloxane (PDMS) stamping methods is demonstrated for the first time. Power conversion efficiency of the moth-eye patterned perovskite solar cell is improved by ≈11%, which mainly results from increasing light harvesting efficiency by structural optical property.