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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 (J sc) 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 J sc 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.

Recently, a lot of attention is being paid to combine silicon nanowires (SiNWs) and the conventional micro-pyramid silicon (µT-Si) structures leading to SiNWs/µT-Si binary structures for efficient light harvesting. We report large-area fabrication of vertical SiNWs array over three-dimensional micro-pyramid structured silicon substrate through silver (Ag)-assisted electroless wet chemical etching in aqueous HF and AgNO3 solution. The influence of AgNO3 concentration has been investigated over the formation of the SiNWs. Vertical SiNWs formation takes place for lower AgNO3 concentrations. For higher concentrations, random formation of NWs and depletion of the micro-pyramids is observed. The present study reveals strong influence of local morphology of micro-pyramids over NWs formation. The formation mechanism of such binary structures has been discussed in co-relation with dimensional features of the micro-pyramids and surface free energy. Such hierarchically textured binary structured silicon surfaces exhibit excellent light trapping properties reducing reflectance to as low as