Solar photons beyond the band gap wavelengths: their effect on solution-processed solar cells

A deep understanding of how solution-processed solar cells (SSCs) perform under varying temperatures and irradiance is crucial for their optimal design, synthesis, and use. However, current partial spectral characterization, primarily below the band gap wavelengths (λ < λ_g), limits insights into their full operation. In this work, we expand the current knowledge by providing comprehensive full-spectrum experimental optical characterizations (∼300-2500 nm) and theoretical optical-thermal-electrical analysis for the most common high-efficiency single-junction and tandem organic SSCs (OSCs) and perovskite SSCs (PSCs), including p-i-n OSC, n-i-p OSC, p-i-n PSC, n-i-p mesoscopic PSC, OSC/PSC, and PSC/PSC. By incorporating solar photons above λ_g in our investigation, we uncover the effects of parasitic absorption (∼300-2500 nm) and conversion losses (λ < λ_g) on operating temperature and power conversion efficiency (PCE) losses, highlighting the conditions, materials, and optimal architectures for reducing device temperature. These improvements could reduce PCE losses by up to ∼7 times compared to conventional silicon wafer-based solar cells in real-world conditions.