This work confirms that radical intermediates are the reactive species in quinhydrone/methanol (QHY/ME) passivation on silicon surfaces. The two constituent parts, p-benzoquinone (BQ) and hydroquinone (HQ), have been studied separately. BQ abstracts the hydrogen atom from methanol to become semiquinone radicals (QH*). Both QH* and the resulting methanol radical are responsible for the large, instantaneous increase in minority carrier lifetime in BQ/ME, obtaining the lowest surface recombination velocity of 1.6 cm/s. HQ releases a hydrogen atom to become QH*. The quinone derivatives containing a lower electronegativity group (Cl or O) on the benzene ring form radicals more easily, and give better passivation results. This radical-driven passivation mechanism is also valid on other radical sources. X-ray photoelectron spectroscopy (XPS) supports the radical mechanism in the observation of dominating BQ bonding after 1 h of BQ/ME treatment, and increasing methanol bonding with increasing immersion time, reaching a roughly 21% SiOSi, 13% ME, and 6% BQ monolayer coverage in 24 h for BQ/ME passivated silicon. Density functional theory (DFT) further confirms the thermodynamic possibility of radical bonding and proves that the “edge-on” single-bonded configuration is more energetically favorable than the “face-on” double-bonded configuration.

Hybrid silicon solar cells have been fabricated by the spin coating of conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as a p-type contact on textured n-type crystalline silicon wafers. The effect of adding co-solvents, ethylene glycol (EG) and dimethyl sulphoxide (DMSO), to PEDOT:PSS improves its conductivity which translates to the improved performance of solar cells. Transfer length measurements were conducted to realize optimal contact with minimal losses between the front metal contact (silver) and PEDOT:PSS. From the conductivity and device results, a 7% EG with 0.25 wt% Triton (surfactant) blend of PEDOT:PSS is found to be optimal for these cells. This current approach with a few changes in the device architecture will pave way for the further improvement of PEDOT:PSS based hybrid silicon solar cells.

Interfacial layers consisting of organic molecules with a permanent dipole moment exhibit enhanced charge carrier selectivity when applied as electron‐selective contacts in crystalline silicon (c‐Si) heterojunction solar cells. It is found that thermal annealing has a detrimental effect on the charge carrier selectivity of dipole materials based on the amino acid l‐histidine mixed with a fluorosurfactant. Although, the implied open‐circuit voltage (iVoc) increases with annealing, the Voc decreases significantly which is accompanied by a decrease in the built‐in voltage (Vbi) and increase in the specific contact resistivity (ρc). Based on numerical device simulations, it is concluded that the tunneling of electrons through the dipole layer becomes less effective with increasing annealing temperature due to the decomposition of the dipole materials. The decomposition leads to a more “resistive” interfacial layer and to a gradient in the electron quasi‐Fermi potential and, thus, a decrease in Voc. Furthermore, storage under ambient air at room temperature degraded the electron‐selective contacts substantially, limiting the potential of the dipole material for the application in silicon organic heterojunction solar cells.

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