Hierarchical structures consisting of micropyramids and nanowires are used in Si/PEDOT:PSS hybrid solar cells to achieve a power conversion efficiency (PCE) up to 11.48% with excellent omnidirectionality. The structure provides a combined concepts of superior light trapping ability, significant increase of p-n junction areas, and short carrier diffusion distance, improving the photovoltaic characteristics including short-circuit current density, fill factor, and PCE. The enhancement of power generation is up to 253.8% at high incident angles, showing the outstanding omnidirectional operation ability of hybrid cells with hierarchical Si surfaces. This properly designed hierarchical-structured device paves a promising way for developing low-cost, high-efficiency, and omnidirectional solar applications in the future.

A novel strategy employing core-shell nanowire arrays (NWAs) consisting of Si/regioregular poly(3-hexylthiophene) (P3HT) was demonstrated to facilitate efficient light harvesting and exciton dissociation/charge collection for hybrid solar cells (HSCs). We experimentally demonstrate broadband and omnidirectional light-harvesting characteristics of core-shell NWA HSCs due to their subwavelength features, further supported by the simulation based on finite-difference time domain analysis. Meanwhile, core-shell geometry of NWA HSCs guarantees efficient charge separation since the thickness of the P3HT shells is comparable to the exciton diffusion length. Consequently, core-shell HSCs exhibit a 61% improvement of short-circuit current for a conversion efficiency (η) enhancement of 31.1% as compared to the P3HT-infiltrated Si NWA HSCs with layers forming a flat air/polymer cell interface. The improvement of crystal quality of P3HT shells due to the formation of ordering structure at Si interfaces after air mass 1.5 global (AM 1.5G) illumination was confirmed by transmission electron microscopy and Raman spectroscopy. The core-shell geometry with the interfacial improvement by AM 1.5G illumination promotes more efficient exciton dissociation and charge separation, leading to η improvement (∼140.6%) due to the considerable increase in V(oc) from 257 to 346 mV, J(sc) from 11.7 to 18.9 mA/cm(2), and FF from 32.2 to 35.2%, which is not observed in conventional P3HT-infiltrated Si NWA HSCs. The stability of the Si/P3HT core-shell NWA HSCs in air ambient was carefully examined. The core-shell geometry should be applicable to many other material systems of solar cells and thus holds high potential in third-generation solar cells.

The conversion efficiency (η) of organic solar cells (OSCs) constructed with ITO/ZnO/P3HT:PCBM/PEDOT:PSS/Ag is improved by incorporating Al into ZnO films (AZO) as electron transport layers (ETLs). Compared with ZnO films, AZO-based OSCs enhance η by ∼13.9% via improving short-circuit photocurrent density from 10.73 to 11.12 mA cm−2 and fill factor from 53.7% to 60.8%. Doping Al into ZnO ETLs not only optimizes band alignment between organic active layers and ETLs and increases carrier concentration, conductivity, and bandgap of ZnO films facilitating more light into OSCs but also improves the absorption of P3HT by promoting the molecular ordering of P3HT.