Low temperature fabrication of PEDOT:PSS/micro-textured silicon-based heterojunction solar cells

Abstract

Organic/inorganic heterojunctions provide a viable option to replace the conventional high-temperature dopant diffusion-based p–n junction owing to their low manufacturing cost. Thus, there has been increasing interests in low temperature heterojunction solar cell concepts particularly polymer/silicon-based heterojunction solar cells. Here, we report fabrication of heterojunction silicon solar cells employing a relatively rapid and solution-based low temperature (~100 °C) process wherein heterojunctions are made by directly spin coating the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), a p-layer on the micro-textured (µT) n-Si substrates. The micro-texturing enhances the surface area as well as reduces reflectance to ~11 % in the spectral range useful for Si solar cell. The role of dimethyl sulfoxide (DMSO) addition in PEDOT:PSS on the performance parameters of the solar cells has been investigated. The PEDOT:PSS layer also acts as a surface passivation layer for n-Si as confirmed by the minority carrier lifetime measurements. Almost threefold enhancement in the photocurrent density (Jsc) and a fivefold improvement in the conversion efficiency (η) for an optimized DMSO addition in the polymer have been observed compared to that having no DMSO addition. As a result, a maximum η of 6.45 % and Jsc of 27.28 mA/cm2 have been achieved under 100 mW/cm2 irradiation at 25 °C. In these cells, open circuit voltage and fill factor are found low, which is the reason for low device efficiency. However, there is a scope for further improvement in device performance by process optimization particularly metal electrodes, PEDOT:PSS/DMSO layer thickness, PEDOT:PSS/DMSO/µT-Si interface properties, and incorporation of back surface field to exploit the full potential of such concepts.