Enhanced stability of P3HT/poly‐crystalline Si thin film hybrid solar cells

Hybrid solar cells have been fabricated from solution processing of poly‐(3‐hexylthiophen‐2,5‐diyl) onto planar poly‐crystalline thin film silicon (poly‐Si) absorbers on glass. The poly‐Si layers were prepared by laser crystallization. Methyl passivation of the poly‐Si surface by a one‐step grafting process via methyl‐Grignard enabled open circuit voltages of up to 552 mV and an overall power conversion efficiency of 6.6% for this device type. The solar cell exhibited significant advantages compared to the wafer‐based counterparts. The inverted device structure of the thin film cell lead to an enhancement of the quantum efficiency since the back side contacted cell had less light absorption and reflection losses due to the gold layer which was used as front contact for the c‐Si‐based hybrid solar cell. As a result, a photo current of 24.3 mA cm−2was obtained for a 10 μm thin poly‐Si layer on glass. Furthermore, the inverted device structure showed a pronounced increase in stability due to the much thicker gold back contact that reduces the diffusion of water and oxygen toward the polymer layer. After 3 months in ambient air, this type of solar cell operated with 86% of its initial efficiency.