# Boosting Organic Solar Cell Performance via Light-Assisted Crystallization of P3HT:PCBM Blend

## TL;DR

This study shows that using light during annealing improves the performance of organic solar cells made with P3HT and PCBM.

## Contribution

The novel contribution is demonstrating that light-assisted annealing enhances crystallinity and efficiency in P3HT:PCBM solar cells.

## Key findings

- Light-assisted annealing improved P3HT crystallinity and in-plane molecular stacking.
- P3HT:PCBM blends with a 1:0.6 ratio achieved higher efficiency with light-assisted annealing.
- Light-assisted annealing reduced charge recombination and improved carrier mobility.

## Abstract

In this study, we
explore the effect of halogen-light-assisted
(LA) annealing on the crystallization of poly­(3-hexylthiophene) (P3HT)
films and the morphology of P3HT:[6,6]-phenyl-C61-butyric acid methyl
ester (PCBM) blends, along with their impact on organic solar cell
performance. Samples were annealed at various temperatures (100–120
°C) and durations (5–15 min) using both conventional hot
plate (HP) and LA methods. Structural analysis showed that LA annealing
significantly enhanced the crystallinity of P3HT films through improved
in-plane molecular stacking. For the P3HT:PCBM blend layers, the best
film quality and device performance were achieved with LA annealing
at 100 °C for 15 min, resulting in a power conversion efficiency
(PCE) of 3.10% compared to 2.22% for the HP-annealed counterpart.
We further evaluated blends with different P3HT:PCBM ratios (1:0.6,
1:1, and 1:1.4) and found that P3HT-rich compositions, especially
1:0.6, benefited most from LA annealing, achieving better film morphology
and higher efficiency. Charge transport and recombination behavior
were studied through time-resolved photoluminescence, light-intensity-dependent J–V, and space charge limited current
measurements. These analyses confirmed that LA annealing improves
charge carrier mobility, reduces trap densities, and minimizes nonradiative
recombination. Overall, our results demonstrate that LA annealing
is an effective and scalable method to enhance both the material quality
and photovoltaic performance in P3HT:PCBM-based solar cells.