Achieving 23.83% conversion efficiency in silicon heterojunction solar cell with ultra‐thin MoO_x hole collector layer via tailoring (i)a‐Si:H/MoO_x interface

Abstract

Thin films of transition metal oxides such as molybdenum oxide (MoOx) are attractive for application in silicon heterojunction solar cells for their potential to yield large short‐circuit current density. However, full control of electrical properties of thin MoOx layers must be mastered to obtain an efficient hole collector. Here, we show that the key to control the MoOx layer quality is the interface between the MoOx and the hydrogenated intrinsic amorphous silicon passivation layer underneath. By means of ab initio modelling, we demonstrate a dipole at such interface and study its minimization in terms of work function variation to enable high performance hole transport. We apply this knowledge to experimentally tailor the oxygen content in MoOx by plasma treatments (PTs). PTs act as a barrier to oxygen diffusion/reaction and result in optimal electrical properties of the MoOx hole collector. With this approach, we can thin down the MoOx thickness to 1.7 nm and demonstrate short‐circuit current density well above 40 mA/cm2 and a champion device exhibiting 23.83% conversion efficiency.

Tunable Hole‐Selective Transport by Solution‐Processed MoO3−x Via Doping for p‐Type Crystalline Silicon Solar Cells

“…Besides, oxygen vacancies can trap electrons, evidenced by electron spin resonance (ESR) measurement (Figure S2, Supporting Information), in which the pristine and Nb 5+ ‐doped MoO 3− x samples possess a similar signal centered at g = 2.0014 as in the ternary metal oxides. [ 26 ] This effect can reduce the recombination probability of electrons and holes, especially considering that oxygen vacancies generate more easily in the film close to the MoO 3− x / p ‐Si interface, [ 19 ] resulting in the increased τ eff and i‐V OC as measured. Nevertheless, excessive doping leads to the formation of a large number of oxygen vacancy defects and the deterioration of film quality, lowering the passivation contact performance.…”

“…[18] The highest efficiency of silicon solar cells based on MoO 3Àx selective contact layer reached 23.83% very recently by suppressing the interfacial oxygen vacancy generation with plasma pretreatment of α-Si:H layer. [19] DOI: 10.1002/solr.202300023 Molybdenum oxide (MoO 3Àx , x < 3) has been successfully used as an efficient hole-selective contact material for crystalline silicon heterojunction solar cells. The carrier transport capability strongly depends on its work function, that is, oxygen vacancies; however, there are lack of effective methods to modulate the multiple oxidation states.…”

“…[ 18 ] The highest efficiency of silicon solar cells based on MoO 3− x selective contact layer reached 23.83% very recently by suppressing the interfacial oxygen vacancy generation with plasma pretreatment of α‐Si:H layer. [ 19 ] Both requirements for efficient hole extraction from induced MoO 3− x /c‐Si heterojunction are suggested to band‐to‐band (B2B) tunneling and trap‐assisted tunneling (TAT). [ 20 ] However, the two transport paths strongly depend on oxygen vacancy concentration in MoO 3− x , that is, the former desires as less oxygen vacancies as possible to obtain high work function, while the latter needs a certain number of oxygen vacancies to assist the tunneling of holes.…”

High-performance perovskite/silicon heterojunction solar cells enabled by industrially compatible post annealing

“…12,13 Dopant-free contacts are expected to reduce the parasitic optical absorption and Auger recombination as well as simplifying the fabrication process. Up till now, various metal oxides, [14][15][16][17][18] fluorides, [19][20][21] nitrides, [22][23][24] oxynitride, 25,26 oxyfluoride and organic polymers, [27][28][29] have been demonstrated as hole-or electron-transport layers for c-Si solar cells. Due to considerable efforts devoted to this topic, the PCE of c-Si solar cells with dopant-free carrier-selective contacts has increased rapidly in these years.…”

Aluminum and Molybdenum Co-Doped Zinc Oxide Films as Dual-Functional Carrier-Selective Contact for Silicon Solar Cells

“…Transition metal oxides (TMOs) play various roles in optoelectronic devices, such as solar cells, photoelectric detectors, organic light-emitting diodes, and so forth. − In recent years, TMOs have been playing a significant role in solar cells, and they are commonly used in silicon solar cells as the transparent conductive oxide (TCO) electrode or carrier selective contact (CSC). − TCOs such as indium tin oxide (ITO), indium tungsten oxide, and aluminum-doped zinc oxide (AZO) have been widely applied on the silicon solar cells as a transparency electrode due to their low sheet resistance and high transparency, and TCO can also provide antireflection effect to enhance light absorption in silicon heterojunction (SHJ) solar cells. ,,,− Due to the undesirable lateral conductivity of the intrinsic a-Si:H films and doped a-Si:H films deposited on the c-Si wafer, TCO is deposited between the a-Si:H layer and the metal grid to ensure that the carriers can be laterally collected to the metal grid with a low resistance.…”