Combining electron‐ and hole‐selective materials in one crystalline silicon (Si) solar cell, thereby avoiding any dopants, is not considered for application to photovoltaic industry until only comparable efficiency and stable performance are achievable. Here, it is demonstrated how a conventionally unstable electron‐selective contact (ESC) is optimized with huge boost in stability as well as improved electron transport. With the introduction of a Ti thin film between a‐Si:H( i )/LiF and Al electrode, high‐level passivation ( S eff = 4.6 cm s –1 ) from a‐Si:H( i ) and preferential band alignment ( ρ C = 7.9 mΩ cm 2 ) from low work function stack of LiF/Ti/Al are both stably retained in the newly constructed n ‐Si/a‐Si:H( i )/LiF/Ti/Al ESC. A detailed interfacial elements analysis reveals that the efficiently blocked inward diffusion of Al from electrode by the Ti protecting layer balances transport and recombination losses in general. This excellent electron‐selective properties in combination with large process tolerance that enable remarkable device performance, particularly high efficiencies of 22.12% and 23.61%, respectively, are successfully approached by heterojunction solar cells with dopant‐free ESC and dopant‐free contacts for both polarities.

Silicon (Si)‐based dopant‐free heterojunction solar cells (SCs) featuring carrier‐selective contacts (CSCs) have attracted considerable interest due to the extreme simplifications in their device structure and manufacturing procedure. However, these SCs are limited by the unsatisfactory contact properties on both sides of the junction, and their efficiencies are not comparable with those of commercially available Si SCs. In this report, a high‐performance silicon‐oxide/magnesium (SiOx/Mg) electron‐selective contact (ESC) design is described. Combining an ultrathin SiOx and a low work function Mg layer, the novel ESC simultaneously yields low recombinative and resistive losses. In addition, deposition of Mg on SiOx relaxes the restriction on the threshold thickness of the SiOx for electron tunneling and therefore broadens the optimization space for rear‐sided passivation. Meanwhile, hole‐selective contact with boosted light harvesting and suppressed interfacial recombination is achieved by forming a fully conformal contact between the conducting poly(3,4‐ethylene dioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) and periodic Si pyramid arrays. With the double‐sided carrier‐selective contact designs, PEDOT: PSS/Si/SiOx/Mg SCs with efficiency of 15% are finally obtained via a totally dopant‐free processing. Subsequent calculations further indicate a pathway for the improvement of these contacts toward an efficiency that is competitive with conventionally diffused pn junction SCs.

Surface nanotexturing with excellent light-trapping property is expected to significantly increase the conversion efficiency of solar cells. However, limited by the serious surface recombination arising from the greatly enlarged surface area, the silicon (Si) nanotexturing-based solar cells cannot yet achieve satisfactory high efficiency, which is more prominent in organic/Si hybrid solar cells (HSCs) where a uniform polymer layer can rarely be conformably coated on nanotextured substrate. Here, the HSCs featuring advanced surface texture of periodic upright nanopyramid (UNP) arrays and hole-conductive conjugated polymers, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), are investigated. The tetramethylammonium hydroxide etching is used to smooth the surface morphologies of the Si-UNPs, leading to reduced surface defect states. The uniform Si-UNPs together with silane chemical-incorporated PEDOT:PSS solution enable the simultaneous realization of excellent broadband light absorption as well as enhanced electrical contact between the textured Si and the conducting polymer. The resulting PEDOT:PSS/Si HSCs textured with UNP arrays show a promising power conversion efficiency of 13.8%, significantly higher than 12.1% of the cells based on the-state-of-the-art surface texture with random pyramids. These results provide a viable route toward shape-controlled nanotexturing-based high-performance organic/Si HSCs.