Molybdenum trioxide (MoOX, X < 3), with a large work function, can induce upward band bending in crystalline silicon (c‐Si) when constructing a heterojunction, which makes it an attractive candidate for hole‐selective contact in c‐Si solar cells. Herein, the passivation property and hole selectivity of MoOX thin films are investigated on p‐type c‐Si wafers using MoOX/aluminum (Al) as rear contacts. To elevate the performance from the aspect of light management, silver (Ag) and copper (Cu) are further used as back electrodes instead of Al. Solar cells with Ag electrodes deliver the best performance with a power conversion efficiency of 18.74%, followed by Cu (17.61%) and Al (16.36%) electrodes, attributing to the better reflectivity of Ag and Cu. It is also noted that solar cells with MoOX/Ag and MoOX/Cu contacts show significant degradation under room temperature storage. The interfacial evolutions are then carefully studied as a function of elevated temperature that accelerate the thermodynamic process. The degradation mechanism involves redox reaction and metal diffusion at the MoOX/metal interfaces. This work points out the importance of selecting the adjacent layers of MoOX and regulating the interfaces to stabilize the MoOX‐based c‐Si solar cells.

Molybdenum oxide (MoO X , X < 3) has been successfully demonstrated as an efficient passivating hole-selective contact in crystalline Si (c-Si) heterojunction solar cells because of its large bandgap (∼3.2 eV) and work function (∼6.9 eV). However, the severe performance degradation coming from the instability of the MoO X and its interfaces has not been well addressed. In this work, we started with a c-Si(p)/MoO X heterojunction solar cell that yielded a power conversion efficiency (PCE) of 15.86%, in which the MoO X film was synthesized by industry-compatible atomic layer deposition (ALD). The initial PCE dropped to 10.20% after 2 days because of severe migration of O and Ag at the MoO X /Ag interface. We solved this by the insertion of a CrO X layer between the MoO X layer and the Ag electrode. The solar cell was found to be stable for more than 8 months in air because of the suppression of interface degradation. Our work demonstrates an effective way of improving the stability of silicon solar cells with transition metal oxide carrier selective contacts.

Crystalline silicon heterojunction solar cells based on hole-selective MoO X contacts provide obvious merits in terms of the decent passivation and carrier selectivity but face the challenge of long-term stability. With the aim to improve the performance and stability of solar cells with full area MoO X / metal contacts, a SiO X tunneling layer on silicon surface is intentionally formed by UV/O 3 treatment and an indium tin oxide (ITO) film is sputtered as a high-work-function electrode. Before ITO sputtering, an ultrathin V 2 O X capping layer is introduced to efficiently prevent MoO X film from air exposure and the damage by sputtering bombardment. The insertion of SiO X , V 2 O X , and ITO keeps the work function of MoO X at a high level, which improves the hole selectivity as well as the stability of the contact. The p-Si/SiO X /MoO X / V 2 O X /ITO/Ag solar cell demonstrates an efficiency of 20.0% with improved stability, which is the highest value for MoO X heterocontacts class on p-type silicon to date.

Nanostructured metal back reflectors (BRs) are playing an important role in thin-film solar cells, which facilitates an increased optical path length within a relatively thin absorbing layer. In this study, three nanotextured plasmonic metal (copper, gold, and silver) BRs underneath flexible thin-film amorphous silicon solar cells are systematically investigated. The solar cells with BRs demonstrate an excellent light harvesting capability in the long-wavelength region. With the combination of hybrid cavity resonances, horizontal modes, and surface plasmonic resonances, more incident light is coupled into the photoactive layer. Compared to the reference cells, the three devices with plasmonic BRs show lower parasitic absorptions with different individual absorption distributions. Both experimental and simulated results indicate that the silver BR cells delivered the best performance with a promising power conversion efficiency of 7.26%. These rational designs of light harvesting nanostructures provide guidelines for high-performance thin-film solar cells and other optoelectronic devices.