# Flash-Infrared-Annealing-Enabled High-Temperature Sintering of Photoanodes on Flexible Polymer Foils for Ultralight Photovoltaics

## TL;DR

This paper introduces a new method to sinter solar cell components on flexible plastic using infrared heating, enabling lightweight and efficient photovoltaic devices.

## Contribution

The novel use of flash infrared annealing enables high-temperature sintering on flexible substrates without damaging them.

## Key findings

- Flexible DSCs achieved a power conversion efficiency of 5.10% under standard illumination.
- Localized IR sintering reduces processing barriers for roll-to-roll printable solar cells.
- Devices have 51× higher specific power compared to glass-based equivalents.

## Abstract

Ultralight photovoltaics are indispensable wherever every
gram
counts, from self-powered Internet of Things nodes to free-hanging
greenhouse covers. In dye-sensitized solar cells (DSCs) the required
450–500 °C sintering of the mesoporous TiO2 (m-TiO2) photoanode has so far limited the use
of polymer substrates. Here, we replace the furnace step with flash
infrared annealing. Near-IR radiation heats the 3.5 μm
m-TiO2 layer to 550 ± 20 °C while keeping
a 12.5 μm indium-tin-oxide/polyimide foil below 170 °C
with a water-cooled heat-sink. We obtain complete removal of organic
binders, while the substrate sheet resistance increases modestly from
60.2 to 129.8 Ω sq–1. Flexible DSCs
reach power conversion efficiencies of 5.10% under AM 1.5G
illumination, a record value for DSCs on sub-25 μm plastics.
The finished devices deliver 51× the specific power of equivalent
glass devices. A cradle-to-gate life cycle assessment normalized to
power-per-mass reveals order-of-magnitude reductions in several categories
compared with rigid hot-plate processing. Localized IR sintering thus
removes the last processing barrier for truly roll-to-roll printable
hybrid solar cells.